linux/drivers/iommu/iommufd/main.c

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// SPDX-License-Identifier: GPL-2.0-only
/* Copyright (C) 2021 Intel Corporation
* Copyright (c) 2021-2022, NVIDIA CORPORATION & AFFILIATES
*
* iommufd provides control over the IOMMU HW objects created by IOMMU kernel
* drivers. IOMMU HW objects revolve around IO page tables that map incoming DMA
* addresses (IOVA) to CPU addresses.
*/
#define pr_fmt(fmt) "iommufd: " fmt
#include <linux/bug.h>
#include <linux/file.h>
#include <linux/fs.h>
#include <linux/iommufd.h>
#include <linux/miscdevice.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/slab.h>
#include <uapi/linux/iommufd.h>
#include "io_pagetable.h"
#include "iommufd_private.h"
#include "iommufd_test.h"
struct iommufd_object_ops {
void (*pre_destroy)(struct iommufd_object *obj);
void (*destroy)(struct iommufd_object *obj);
void (*abort)(struct iommufd_object *obj);
};
static const struct iommufd_object_ops iommufd_object_ops[];
static struct miscdevice vfio_misc_dev;
struct iommufd_object *_iommufd_object_alloc(struct iommufd_ctx *ictx,
size_t size,
enum iommufd_object_type type)
{
struct iommufd_object *obj;
int rc;
obj = kzalloc(size, GFP_KERNEL_ACCOUNT);
if (!obj)
return ERR_PTR(-ENOMEM);
obj->type = type;
/* Starts out bias'd by 1 until it is removed from the xarray */
refcount_set(&obj->wait_cnt, 1);
refcount_set(&obj->users, 1);
/*
* Reserve an ID in the xarray but do not publish the pointer yet since
* the caller hasn't initialized it yet. Once the pointer is published
* in the xarray and visible to other threads we can't reliably destroy
* it anymore, so the caller must complete all errorable operations
* before calling iommufd_object_finalize().
*/
rc = xa_alloc(&ictx->objects, &obj->id, XA_ZERO_ENTRY, xa_limit_31b,
GFP_KERNEL_ACCOUNT);
if (rc)
goto out_free;
return obj;
out_free:
kfree(obj);
return ERR_PTR(rc);
}
struct iommufd_object *_iommufd_object_alloc_ucmd(struct iommufd_ucmd *ucmd,
size_t size,
enum iommufd_object_type type)
{
struct iommufd_object *new_obj;
/* Something is coded wrong if this is hit */
if (WARN_ON(ucmd->new_obj))
return ERR_PTR(-EBUSY);
/*
* An abort op means that its caller needs to invoke it within a lock in
* the caller. So it doesn't work with _iommufd_object_alloc_ucmd() that
* will invoke the abort op in iommufd_object_abort_and_destroy(), which
* must be outside the caller's lock.
*/
if (WARN_ON(iommufd_object_ops[type].abort))
return ERR_PTR(-EOPNOTSUPP);
new_obj = _iommufd_object_alloc(ucmd->ictx, size, type);
if (IS_ERR(new_obj))
return new_obj;
ucmd->new_obj = new_obj;
return new_obj;
}
/*
* Allow concurrent access to the object.
*
* Once another thread can see the object pointer it can prevent object
* destruction. Expect for special kernel-only objects there is no in-kernel way
* to reliably destroy a single object. Thus all APIs that are creating objects
* must use iommufd_object_abort() to handle their errors and only call
* iommufd_object_finalize() once object creation cannot fail.
*/
void iommufd_object_finalize(struct iommufd_ctx *ictx,
struct iommufd_object *obj)
{
XA_STATE(xas, &ictx->objects, obj->id);
void *old;
xa_lock(&ictx->objects);
old = xas_store(&xas, obj);
xa_unlock(&ictx->objects);
/* obj->id was returned from xa_alloc() so the xas_store() cannot fail */
WARN_ON(old != XA_ZERO_ENTRY);
}
/* Undo _iommufd_object_alloc() if iommufd_object_finalize() was not called */
void iommufd_object_abort(struct iommufd_ctx *ictx, struct iommufd_object *obj)
{
XA_STATE(xas, &ictx->objects, obj->id);
void *old;
xa_lock(&ictx->objects);
old = xas_store(&xas, NULL);
xa_unlock(&ictx->objects);
WARN_ON(old != XA_ZERO_ENTRY);
kfree(obj);
}
/*
* Abort an object that has been fully initialized and needs destroy, but has
* not been finalized.
*/
void iommufd_object_abort_and_destroy(struct iommufd_ctx *ictx,
struct iommufd_object *obj)
{
if (iommufd_object_ops[obj->type].abort)
iommufd_object_ops[obj->type].abort(obj);
else
iommufd_object_ops[obj->type].destroy(obj);
iommufd_object_abort(ictx, obj);
}
struct iommufd_object *iommufd_get_object(struct iommufd_ctx *ictx, u32 id,
enum iommufd_object_type type)
{
struct iommufd_object *obj;
if (iommufd_should_fail())
return ERR_PTR(-ENOENT);
xa_lock(&ictx->objects);
obj = xa_load(&ictx->objects, id);
if (!obj || (type != IOMMUFD_OBJ_ANY && obj->type != type) ||
!iommufd_lock_obj(obj))
obj = ERR_PTR(-ENOENT);
xa_unlock(&ictx->objects);
return obj;
}
static int iommufd_object_dec_wait(struct iommufd_ctx *ictx,
struct iommufd_object *to_destroy)
iommufd: Do not UAF during iommufd_put_object() The mixture of kernel and user space lifecycle objects continues to be complicated inside iommufd. The obj->destroy_rwsem is used to bring order to the kernel driver destruction sequence but it cannot be sequenced right with the other refcounts so we end up possibly UAF'ing: BUG: KASAN: slab-use-after-free in __up_read+0x627/0x750 kernel/locking/rwsem.c:1342 Read of size 8 at addr ffff888073cde868 by task syz-executor934/6535 CPU: 1 PID: 6535 Comm: syz-executor934 Not tainted 6.6.0-rc7-syzkaller-00195-g2af9b20dbb39 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/09/2023 Call Trace: <TASK> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xd9/0x1b0 lib/dump_stack.c:106 print_address_description mm/kasan/report.c:364 [inline] print_report+0xc4/0x620 mm/kasan/report.c:475 kasan_report+0xda/0x110 mm/kasan/report.c:588 __up_read+0x627/0x750 kernel/locking/rwsem.c:1342 iommufd_put_object drivers/iommu/iommufd/iommufd_private.h:149 [inline] iommufd_vfio_ioas+0x46c/0x580 drivers/iommu/iommufd/vfio_compat.c:146 iommufd_fops_ioctl+0x347/0x4d0 drivers/iommu/iommufd/main.c:398 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:871 [inline] __se_sys_ioctl fs/ioctl.c:857 [inline] __x64_sys_ioctl+0x18f/0x210 fs/ioctl.c:857 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd There are two races here, the more obvious one: CPU 0 CPU 1 iommufd_put_object() iommufd_destroy() refcount_dec(&obj->users) iommufd_object_remove() kfree() up_read(&obj->destroy_rwsem) // Boom And there is also perhaps some possibility that the rwsem could hit an issue: CPU 0 CPU 1 iommufd_put_object() iommufd_object_destroy_user() refcount_dec(&obj->users); down_write(&obj->destroy_rwsem) up_read(&obj->destroy_rwsem); atomic_long_or(RWSEM_FLAG_WAITERS, &sem->count); tmp = atomic_long_add_return_release() rwsem_try_write_lock() iommufd_object_remove() up_write(&obj->destroy_rwsem) kfree() clear_nonspinnable() // Boom Fix this by reorganizing this again so that two refcounts are used to keep track of things with a rule that users == 0 && shortterm_users == 0 means no other threads have that memory. Put a wait_queue in the iommufd_ctx object that is triggered when any sub object reaches a 0 shortterm_users. This allows the same wait for userspace ioctls to finish behavior that the rwsem was providing. This is weaker still than the prior versions: - There is no bias on shortterm_users so if some thread is waiting to destroy other threads can continue to get new read sides - If destruction fails, eg because of an active in-kernel user, then shortterm_users will have cycled to zero momentarily blocking new users - If userspace races destroy with other userspace operations they continue to get an EBUSY since we still can't intermix looking up an ID and sleeping for its unref In all cases these are things that userspace brings on itself, correct programs will not hit them. Fixes: 99f98a7c0d69 ("iommufd: IOMMUFD_DESTROY should not increase the refcount") Link: https://lore.kernel.org/all/2-v2-ca9e00171c5b+123-iommufd_syz4_jgg@nvidia.com/ Reported-by: syzbot+d31adfb277377ef8fcba@syzkaller.appspotmail.com Closes: https://lore.kernel.org/r/00000000000055ef9a0609336580@google.com Reviewed-by: Kevin Tian <kevin.tian@intel.com> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
2023-11-12 15:44:08 -04:00
{
if (refcount_dec_and_test(&to_destroy->wait_cnt))
iommufd: Do not UAF during iommufd_put_object() The mixture of kernel and user space lifecycle objects continues to be complicated inside iommufd. The obj->destroy_rwsem is used to bring order to the kernel driver destruction sequence but it cannot be sequenced right with the other refcounts so we end up possibly UAF'ing: BUG: KASAN: slab-use-after-free in __up_read+0x627/0x750 kernel/locking/rwsem.c:1342 Read of size 8 at addr ffff888073cde868 by task syz-executor934/6535 CPU: 1 PID: 6535 Comm: syz-executor934 Not tainted 6.6.0-rc7-syzkaller-00195-g2af9b20dbb39 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/09/2023 Call Trace: <TASK> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xd9/0x1b0 lib/dump_stack.c:106 print_address_description mm/kasan/report.c:364 [inline] print_report+0xc4/0x620 mm/kasan/report.c:475 kasan_report+0xda/0x110 mm/kasan/report.c:588 __up_read+0x627/0x750 kernel/locking/rwsem.c:1342 iommufd_put_object drivers/iommu/iommufd/iommufd_private.h:149 [inline] iommufd_vfio_ioas+0x46c/0x580 drivers/iommu/iommufd/vfio_compat.c:146 iommufd_fops_ioctl+0x347/0x4d0 drivers/iommu/iommufd/main.c:398 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:871 [inline] __se_sys_ioctl fs/ioctl.c:857 [inline] __x64_sys_ioctl+0x18f/0x210 fs/ioctl.c:857 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd There are two races here, the more obvious one: CPU 0 CPU 1 iommufd_put_object() iommufd_destroy() refcount_dec(&obj->users) iommufd_object_remove() kfree() up_read(&obj->destroy_rwsem) // Boom And there is also perhaps some possibility that the rwsem could hit an issue: CPU 0 CPU 1 iommufd_put_object() iommufd_object_destroy_user() refcount_dec(&obj->users); down_write(&obj->destroy_rwsem) up_read(&obj->destroy_rwsem); atomic_long_or(RWSEM_FLAG_WAITERS, &sem->count); tmp = atomic_long_add_return_release() rwsem_try_write_lock() iommufd_object_remove() up_write(&obj->destroy_rwsem) kfree() clear_nonspinnable() // Boom Fix this by reorganizing this again so that two refcounts are used to keep track of things with a rule that users == 0 && shortterm_users == 0 means no other threads have that memory. Put a wait_queue in the iommufd_ctx object that is triggered when any sub object reaches a 0 shortterm_users. This allows the same wait for userspace ioctls to finish behavior that the rwsem was providing. This is weaker still than the prior versions: - There is no bias on shortterm_users so if some thread is waiting to destroy other threads can continue to get new read sides - If destruction fails, eg because of an active in-kernel user, then shortterm_users will have cycled to zero momentarily blocking new users - If userspace races destroy with other userspace operations they continue to get an EBUSY since we still can't intermix looking up an ID and sleeping for its unref In all cases these are things that userspace brings on itself, correct programs will not hit them. Fixes: 99f98a7c0d69 ("iommufd: IOMMUFD_DESTROY should not increase the refcount") Link: https://lore.kernel.org/all/2-v2-ca9e00171c5b+123-iommufd_syz4_jgg@nvidia.com/ Reported-by: syzbot+d31adfb277377ef8fcba@syzkaller.appspotmail.com Closes: https://lore.kernel.org/r/00000000000055ef9a0609336580@google.com Reviewed-by: Kevin Tian <kevin.tian@intel.com> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
2023-11-12 15:44:08 -04:00
return 0;
if (iommufd_object_ops[to_destroy->type].pre_destroy)
iommufd_object_ops[to_destroy->type].pre_destroy(to_destroy);
iommufd: Do not UAF during iommufd_put_object() The mixture of kernel and user space lifecycle objects continues to be complicated inside iommufd. The obj->destroy_rwsem is used to bring order to the kernel driver destruction sequence but it cannot be sequenced right with the other refcounts so we end up possibly UAF'ing: BUG: KASAN: slab-use-after-free in __up_read+0x627/0x750 kernel/locking/rwsem.c:1342 Read of size 8 at addr ffff888073cde868 by task syz-executor934/6535 CPU: 1 PID: 6535 Comm: syz-executor934 Not tainted 6.6.0-rc7-syzkaller-00195-g2af9b20dbb39 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/09/2023 Call Trace: <TASK> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xd9/0x1b0 lib/dump_stack.c:106 print_address_description mm/kasan/report.c:364 [inline] print_report+0xc4/0x620 mm/kasan/report.c:475 kasan_report+0xda/0x110 mm/kasan/report.c:588 __up_read+0x627/0x750 kernel/locking/rwsem.c:1342 iommufd_put_object drivers/iommu/iommufd/iommufd_private.h:149 [inline] iommufd_vfio_ioas+0x46c/0x580 drivers/iommu/iommufd/vfio_compat.c:146 iommufd_fops_ioctl+0x347/0x4d0 drivers/iommu/iommufd/main.c:398 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:871 [inline] __se_sys_ioctl fs/ioctl.c:857 [inline] __x64_sys_ioctl+0x18f/0x210 fs/ioctl.c:857 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd There are two races here, the more obvious one: CPU 0 CPU 1 iommufd_put_object() iommufd_destroy() refcount_dec(&obj->users) iommufd_object_remove() kfree() up_read(&obj->destroy_rwsem) // Boom And there is also perhaps some possibility that the rwsem could hit an issue: CPU 0 CPU 1 iommufd_put_object() iommufd_object_destroy_user() refcount_dec(&obj->users); down_write(&obj->destroy_rwsem) up_read(&obj->destroy_rwsem); atomic_long_or(RWSEM_FLAG_WAITERS, &sem->count); tmp = atomic_long_add_return_release() rwsem_try_write_lock() iommufd_object_remove() up_write(&obj->destroy_rwsem) kfree() clear_nonspinnable() // Boom Fix this by reorganizing this again so that two refcounts are used to keep track of things with a rule that users == 0 && shortterm_users == 0 means no other threads have that memory. Put a wait_queue in the iommufd_ctx object that is triggered when any sub object reaches a 0 shortterm_users. This allows the same wait for userspace ioctls to finish behavior that the rwsem was providing. This is weaker still than the prior versions: - There is no bias on shortterm_users so if some thread is waiting to destroy other threads can continue to get new read sides - If destruction fails, eg because of an active in-kernel user, then shortterm_users will have cycled to zero momentarily blocking new users - If userspace races destroy with other userspace operations they continue to get an EBUSY since we still can't intermix looking up an ID and sleeping for its unref In all cases these are things that userspace brings on itself, correct programs will not hit them. Fixes: 99f98a7c0d69 ("iommufd: IOMMUFD_DESTROY should not increase the refcount") Link: https://lore.kernel.org/all/2-v2-ca9e00171c5b+123-iommufd_syz4_jgg@nvidia.com/ Reported-by: syzbot+d31adfb277377ef8fcba@syzkaller.appspotmail.com Closes: https://lore.kernel.org/r/00000000000055ef9a0609336580@google.com Reviewed-by: Kevin Tian <kevin.tian@intel.com> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
2023-11-12 15:44:08 -04:00
if (wait_event_timeout(ictx->destroy_wait,
refcount_read(&to_destroy->wait_cnt) == 0,
msecs_to_jiffies(60000)))
iommufd: Do not UAF during iommufd_put_object() The mixture of kernel and user space lifecycle objects continues to be complicated inside iommufd. The obj->destroy_rwsem is used to bring order to the kernel driver destruction sequence but it cannot be sequenced right with the other refcounts so we end up possibly UAF'ing: BUG: KASAN: slab-use-after-free in __up_read+0x627/0x750 kernel/locking/rwsem.c:1342 Read of size 8 at addr ffff888073cde868 by task syz-executor934/6535 CPU: 1 PID: 6535 Comm: syz-executor934 Not tainted 6.6.0-rc7-syzkaller-00195-g2af9b20dbb39 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/09/2023 Call Trace: <TASK> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xd9/0x1b0 lib/dump_stack.c:106 print_address_description mm/kasan/report.c:364 [inline] print_report+0xc4/0x620 mm/kasan/report.c:475 kasan_report+0xda/0x110 mm/kasan/report.c:588 __up_read+0x627/0x750 kernel/locking/rwsem.c:1342 iommufd_put_object drivers/iommu/iommufd/iommufd_private.h:149 [inline] iommufd_vfio_ioas+0x46c/0x580 drivers/iommu/iommufd/vfio_compat.c:146 iommufd_fops_ioctl+0x347/0x4d0 drivers/iommu/iommufd/main.c:398 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:871 [inline] __se_sys_ioctl fs/ioctl.c:857 [inline] __x64_sys_ioctl+0x18f/0x210 fs/ioctl.c:857 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd There are two races here, the more obvious one: CPU 0 CPU 1 iommufd_put_object() iommufd_destroy() refcount_dec(&obj->users) iommufd_object_remove() kfree() up_read(&obj->destroy_rwsem) // Boom And there is also perhaps some possibility that the rwsem could hit an issue: CPU 0 CPU 1 iommufd_put_object() iommufd_object_destroy_user() refcount_dec(&obj->users); down_write(&obj->destroy_rwsem) up_read(&obj->destroy_rwsem); atomic_long_or(RWSEM_FLAG_WAITERS, &sem->count); tmp = atomic_long_add_return_release() rwsem_try_write_lock() iommufd_object_remove() up_write(&obj->destroy_rwsem) kfree() clear_nonspinnable() // Boom Fix this by reorganizing this again so that two refcounts are used to keep track of things with a rule that users == 0 && shortterm_users == 0 means no other threads have that memory. Put a wait_queue in the iommufd_ctx object that is triggered when any sub object reaches a 0 shortterm_users. This allows the same wait for userspace ioctls to finish behavior that the rwsem was providing. This is weaker still than the prior versions: - There is no bias on shortterm_users so if some thread is waiting to destroy other threads can continue to get new read sides - If destruction fails, eg because of an active in-kernel user, then shortterm_users will have cycled to zero momentarily blocking new users - If userspace races destroy with other userspace operations they continue to get an EBUSY since we still can't intermix looking up an ID and sleeping for its unref In all cases these are things that userspace brings on itself, correct programs will not hit them. Fixes: 99f98a7c0d69 ("iommufd: IOMMUFD_DESTROY should not increase the refcount") Link: https://lore.kernel.org/all/2-v2-ca9e00171c5b+123-iommufd_syz4_jgg@nvidia.com/ Reported-by: syzbot+d31adfb277377ef8fcba@syzkaller.appspotmail.com Closes: https://lore.kernel.org/r/00000000000055ef9a0609336580@google.com Reviewed-by: Kevin Tian <kevin.tian@intel.com> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
2023-11-12 15:44:08 -04:00
return 0;
pr_crit("Time out waiting for iommufd object to become free\n");
refcount_inc(&to_destroy->wait_cnt);
iommufd: Do not UAF during iommufd_put_object() The mixture of kernel and user space lifecycle objects continues to be complicated inside iommufd. The obj->destroy_rwsem is used to bring order to the kernel driver destruction sequence but it cannot be sequenced right with the other refcounts so we end up possibly UAF'ing: BUG: KASAN: slab-use-after-free in __up_read+0x627/0x750 kernel/locking/rwsem.c:1342 Read of size 8 at addr ffff888073cde868 by task syz-executor934/6535 CPU: 1 PID: 6535 Comm: syz-executor934 Not tainted 6.6.0-rc7-syzkaller-00195-g2af9b20dbb39 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/09/2023 Call Trace: <TASK> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xd9/0x1b0 lib/dump_stack.c:106 print_address_description mm/kasan/report.c:364 [inline] print_report+0xc4/0x620 mm/kasan/report.c:475 kasan_report+0xda/0x110 mm/kasan/report.c:588 __up_read+0x627/0x750 kernel/locking/rwsem.c:1342 iommufd_put_object drivers/iommu/iommufd/iommufd_private.h:149 [inline] iommufd_vfio_ioas+0x46c/0x580 drivers/iommu/iommufd/vfio_compat.c:146 iommufd_fops_ioctl+0x347/0x4d0 drivers/iommu/iommufd/main.c:398 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:871 [inline] __se_sys_ioctl fs/ioctl.c:857 [inline] __x64_sys_ioctl+0x18f/0x210 fs/ioctl.c:857 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd There are two races here, the more obvious one: CPU 0 CPU 1 iommufd_put_object() iommufd_destroy() refcount_dec(&obj->users) iommufd_object_remove() kfree() up_read(&obj->destroy_rwsem) // Boom And there is also perhaps some possibility that the rwsem could hit an issue: CPU 0 CPU 1 iommufd_put_object() iommufd_object_destroy_user() refcount_dec(&obj->users); down_write(&obj->destroy_rwsem) up_read(&obj->destroy_rwsem); atomic_long_or(RWSEM_FLAG_WAITERS, &sem->count); tmp = atomic_long_add_return_release() rwsem_try_write_lock() iommufd_object_remove() up_write(&obj->destroy_rwsem) kfree() clear_nonspinnable() // Boom Fix this by reorganizing this again so that two refcounts are used to keep track of things with a rule that users == 0 && shortterm_users == 0 means no other threads have that memory. Put a wait_queue in the iommufd_ctx object that is triggered when any sub object reaches a 0 shortterm_users. This allows the same wait for userspace ioctls to finish behavior that the rwsem was providing. This is weaker still than the prior versions: - There is no bias on shortterm_users so if some thread is waiting to destroy other threads can continue to get new read sides - If destruction fails, eg because of an active in-kernel user, then shortterm_users will have cycled to zero momentarily blocking new users - If userspace races destroy with other userspace operations they continue to get an EBUSY since we still can't intermix looking up an ID and sleeping for its unref In all cases these are things that userspace brings on itself, correct programs will not hit them. Fixes: 99f98a7c0d69 ("iommufd: IOMMUFD_DESTROY should not increase the refcount") Link: https://lore.kernel.org/all/2-v2-ca9e00171c5b+123-iommufd_syz4_jgg@nvidia.com/ Reported-by: syzbot+d31adfb277377ef8fcba@syzkaller.appspotmail.com Closes: https://lore.kernel.org/r/00000000000055ef9a0609336580@google.com Reviewed-by: Kevin Tian <kevin.tian@intel.com> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
2023-11-12 15:44:08 -04:00
return -EBUSY;
}
iommufd: IOMMUFD_DESTROY should not increase the refcount syzkaller found a race where IOMMUFD_DESTROY increments the refcount: obj = iommufd_get_object(ucmd->ictx, cmd->id, IOMMUFD_OBJ_ANY); if (IS_ERR(obj)) return PTR_ERR(obj); iommufd_ref_to_users(obj); /* See iommufd_ref_to_users() */ if (!iommufd_object_destroy_user(ucmd->ictx, obj)) As part of the sequence to join the two existing primitives together. Allowing the refcount the be elevated without holding the destroy_rwsem violates the assumption that all temporary refcount elevations are protected by destroy_rwsem. Racing IOMMUFD_DESTROY with iommufd_object_destroy_user() will cause spurious failures: WARNING: CPU: 0 PID: 3076 at drivers/iommu/iommufd/device.c:477 iommufd_access_destroy+0x18/0x20 drivers/iommu/iommufd/device.c:478 Modules linked in: CPU: 0 PID: 3076 Comm: syz-executor.0 Not tainted 6.3.0-rc1-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/03/2023 RIP: 0010:iommufd_access_destroy+0x18/0x20 drivers/iommu/iommufd/device.c:477 Code: e8 3d 4e 00 00 84 c0 74 01 c3 0f 0b c3 0f 1f 44 00 00 f3 0f 1e fa 48 89 fe 48 8b bf a8 00 00 00 e8 1d 4e 00 00 84 c0 74 01 c3 <0f> 0b c3 0f 1f 44 00 00 41 57 41 56 41 55 4c 8d ae d0 00 00 00 41 RSP: 0018:ffffc90003067e08 EFLAGS: 00010246 RAX: 0000000000000000 RBX: ffff888109ea0300 RCX: 0000000000000000 RDX: 0000000000000001 RSI: 0000000000000000 RDI: 00000000ffffffff RBP: 0000000000000004 R08: 0000000000000000 R09: ffff88810bbb3500 R10: ffff88810bbb3e48 R11: 0000000000000000 R12: ffffc90003067e88 R13: ffffc90003067ea8 R14: ffff888101249800 R15: 00000000fffffffe FS: 00007ff7254fe6c0(0000) GS:ffff888237c00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000555557262da8 CR3: 000000010a6fd000 CR4: 0000000000350ef0 Call Trace: <TASK> iommufd_test_create_access drivers/iommu/iommufd/selftest.c:596 [inline] iommufd_test+0x71c/0xcf0 drivers/iommu/iommufd/selftest.c:813 iommufd_fops_ioctl+0x10f/0x1b0 drivers/iommu/iommufd/main.c:337 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:870 [inline] __se_sys_ioctl fs/ioctl.c:856 [inline] __x64_sys_ioctl+0x84/0xc0 fs/ioctl.c:856 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x38/0x80 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd The solution is to not increment the refcount on the IOMMUFD_DESTROY path at all. Instead use the xa_lock to serialize everything. The refcount check == 1 and xa_erase can be done under a single critical region. This avoids the need for any refcount incrementing. It has the downside that if userspace races destroy with other operations it will get an EBUSY instead of waiting, but this is kind of racing is already dangerous. Fixes: 2ff4bed7fee7 ("iommufd: File descriptor, context, kconfig and makefiles") Link: https://lore.kernel.org/r/2-v1-85aacb2af554+bc-iommufd_syz3_jgg@nvidia.com Reviewed-by: Kevin Tian <kevin.tian@intel.com> Reported-by: syzbot+7574ebfe589049630608@syzkaller.appspotmail.com Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
2023-07-25 16:05:49 -03:00
/*
* Remove the given object id from the xarray if the only reference to the
iommufd: Do not UAF during iommufd_put_object() The mixture of kernel and user space lifecycle objects continues to be complicated inside iommufd. The obj->destroy_rwsem is used to bring order to the kernel driver destruction sequence but it cannot be sequenced right with the other refcounts so we end up possibly UAF'ing: BUG: KASAN: slab-use-after-free in __up_read+0x627/0x750 kernel/locking/rwsem.c:1342 Read of size 8 at addr ffff888073cde868 by task syz-executor934/6535 CPU: 1 PID: 6535 Comm: syz-executor934 Not tainted 6.6.0-rc7-syzkaller-00195-g2af9b20dbb39 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/09/2023 Call Trace: <TASK> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xd9/0x1b0 lib/dump_stack.c:106 print_address_description mm/kasan/report.c:364 [inline] print_report+0xc4/0x620 mm/kasan/report.c:475 kasan_report+0xda/0x110 mm/kasan/report.c:588 __up_read+0x627/0x750 kernel/locking/rwsem.c:1342 iommufd_put_object drivers/iommu/iommufd/iommufd_private.h:149 [inline] iommufd_vfio_ioas+0x46c/0x580 drivers/iommu/iommufd/vfio_compat.c:146 iommufd_fops_ioctl+0x347/0x4d0 drivers/iommu/iommufd/main.c:398 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:871 [inline] __se_sys_ioctl fs/ioctl.c:857 [inline] __x64_sys_ioctl+0x18f/0x210 fs/ioctl.c:857 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd There are two races here, the more obvious one: CPU 0 CPU 1 iommufd_put_object() iommufd_destroy() refcount_dec(&obj->users) iommufd_object_remove() kfree() up_read(&obj->destroy_rwsem) // Boom And there is also perhaps some possibility that the rwsem could hit an issue: CPU 0 CPU 1 iommufd_put_object() iommufd_object_destroy_user() refcount_dec(&obj->users); down_write(&obj->destroy_rwsem) up_read(&obj->destroy_rwsem); atomic_long_or(RWSEM_FLAG_WAITERS, &sem->count); tmp = atomic_long_add_return_release() rwsem_try_write_lock() iommufd_object_remove() up_write(&obj->destroy_rwsem) kfree() clear_nonspinnable() // Boom Fix this by reorganizing this again so that two refcounts are used to keep track of things with a rule that users == 0 && shortterm_users == 0 means no other threads have that memory. Put a wait_queue in the iommufd_ctx object that is triggered when any sub object reaches a 0 shortterm_users. This allows the same wait for userspace ioctls to finish behavior that the rwsem was providing. This is weaker still than the prior versions: - There is no bias on shortterm_users so if some thread is waiting to destroy other threads can continue to get new read sides - If destruction fails, eg because of an active in-kernel user, then shortterm_users will have cycled to zero momentarily blocking new users - If userspace races destroy with other userspace operations they continue to get an EBUSY since we still can't intermix looking up an ID and sleeping for its unref In all cases these are things that userspace brings on itself, correct programs will not hit them. Fixes: 99f98a7c0d69 ("iommufd: IOMMUFD_DESTROY should not increase the refcount") Link: https://lore.kernel.org/all/2-v2-ca9e00171c5b+123-iommufd_syz4_jgg@nvidia.com/ Reported-by: syzbot+d31adfb277377ef8fcba@syzkaller.appspotmail.com Closes: https://lore.kernel.org/r/00000000000055ef9a0609336580@google.com Reviewed-by: Kevin Tian <kevin.tian@intel.com> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
2023-11-12 15:44:08 -04:00
* object is held by the xarray.
iommufd: IOMMUFD_DESTROY should not increase the refcount syzkaller found a race where IOMMUFD_DESTROY increments the refcount: obj = iommufd_get_object(ucmd->ictx, cmd->id, IOMMUFD_OBJ_ANY); if (IS_ERR(obj)) return PTR_ERR(obj); iommufd_ref_to_users(obj); /* See iommufd_ref_to_users() */ if (!iommufd_object_destroy_user(ucmd->ictx, obj)) As part of the sequence to join the two existing primitives together. Allowing the refcount the be elevated without holding the destroy_rwsem violates the assumption that all temporary refcount elevations are protected by destroy_rwsem. Racing IOMMUFD_DESTROY with iommufd_object_destroy_user() will cause spurious failures: WARNING: CPU: 0 PID: 3076 at drivers/iommu/iommufd/device.c:477 iommufd_access_destroy+0x18/0x20 drivers/iommu/iommufd/device.c:478 Modules linked in: CPU: 0 PID: 3076 Comm: syz-executor.0 Not tainted 6.3.0-rc1-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/03/2023 RIP: 0010:iommufd_access_destroy+0x18/0x20 drivers/iommu/iommufd/device.c:477 Code: e8 3d 4e 00 00 84 c0 74 01 c3 0f 0b c3 0f 1f 44 00 00 f3 0f 1e fa 48 89 fe 48 8b bf a8 00 00 00 e8 1d 4e 00 00 84 c0 74 01 c3 <0f> 0b c3 0f 1f 44 00 00 41 57 41 56 41 55 4c 8d ae d0 00 00 00 41 RSP: 0018:ffffc90003067e08 EFLAGS: 00010246 RAX: 0000000000000000 RBX: ffff888109ea0300 RCX: 0000000000000000 RDX: 0000000000000001 RSI: 0000000000000000 RDI: 00000000ffffffff RBP: 0000000000000004 R08: 0000000000000000 R09: ffff88810bbb3500 R10: ffff88810bbb3e48 R11: 0000000000000000 R12: ffffc90003067e88 R13: ffffc90003067ea8 R14: ffff888101249800 R15: 00000000fffffffe FS: 00007ff7254fe6c0(0000) GS:ffff888237c00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000555557262da8 CR3: 000000010a6fd000 CR4: 0000000000350ef0 Call Trace: <TASK> iommufd_test_create_access drivers/iommu/iommufd/selftest.c:596 [inline] iommufd_test+0x71c/0xcf0 drivers/iommu/iommufd/selftest.c:813 iommufd_fops_ioctl+0x10f/0x1b0 drivers/iommu/iommufd/main.c:337 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:870 [inline] __se_sys_ioctl fs/ioctl.c:856 [inline] __x64_sys_ioctl+0x84/0xc0 fs/ioctl.c:856 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x38/0x80 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd The solution is to not increment the refcount on the IOMMUFD_DESTROY path at all. Instead use the xa_lock to serialize everything. The refcount check == 1 and xa_erase can be done under a single critical region. This avoids the need for any refcount incrementing. It has the downside that if userspace races destroy with other operations it will get an EBUSY instead of waiting, but this is kind of racing is already dangerous. Fixes: 2ff4bed7fee7 ("iommufd: File descriptor, context, kconfig and makefiles") Link: https://lore.kernel.org/r/2-v1-85aacb2af554+bc-iommufd_syz3_jgg@nvidia.com Reviewed-by: Kevin Tian <kevin.tian@intel.com> Reported-by: syzbot+7574ebfe589049630608@syzkaller.appspotmail.com Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
2023-07-25 16:05:49 -03:00
*/
iommufd: Do not UAF during iommufd_put_object() The mixture of kernel and user space lifecycle objects continues to be complicated inside iommufd. The obj->destroy_rwsem is used to bring order to the kernel driver destruction sequence but it cannot be sequenced right with the other refcounts so we end up possibly UAF'ing: BUG: KASAN: slab-use-after-free in __up_read+0x627/0x750 kernel/locking/rwsem.c:1342 Read of size 8 at addr ffff888073cde868 by task syz-executor934/6535 CPU: 1 PID: 6535 Comm: syz-executor934 Not tainted 6.6.0-rc7-syzkaller-00195-g2af9b20dbb39 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/09/2023 Call Trace: <TASK> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xd9/0x1b0 lib/dump_stack.c:106 print_address_description mm/kasan/report.c:364 [inline] print_report+0xc4/0x620 mm/kasan/report.c:475 kasan_report+0xda/0x110 mm/kasan/report.c:588 __up_read+0x627/0x750 kernel/locking/rwsem.c:1342 iommufd_put_object drivers/iommu/iommufd/iommufd_private.h:149 [inline] iommufd_vfio_ioas+0x46c/0x580 drivers/iommu/iommufd/vfio_compat.c:146 iommufd_fops_ioctl+0x347/0x4d0 drivers/iommu/iommufd/main.c:398 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:871 [inline] __se_sys_ioctl fs/ioctl.c:857 [inline] __x64_sys_ioctl+0x18f/0x210 fs/ioctl.c:857 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd There are two races here, the more obvious one: CPU 0 CPU 1 iommufd_put_object() iommufd_destroy() refcount_dec(&obj->users) iommufd_object_remove() kfree() up_read(&obj->destroy_rwsem) // Boom And there is also perhaps some possibility that the rwsem could hit an issue: CPU 0 CPU 1 iommufd_put_object() iommufd_object_destroy_user() refcount_dec(&obj->users); down_write(&obj->destroy_rwsem) up_read(&obj->destroy_rwsem); atomic_long_or(RWSEM_FLAG_WAITERS, &sem->count); tmp = atomic_long_add_return_release() rwsem_try_write_lock() iommufd_object_remove() up_write(&obj->destroy_rwsem) kfree() clear_nonspinnable() // Boom Fix this by reorganizing this again so that two refcounts are used to keep track of things with a rule that users == 0 && shortterm_users == 0 means no other threads have that memory. Put a wait_queue in the iommufd_ctx object that is triggered when any sub object reaches a 0 shortterm_users. This allows the same wait for userspace ioctls to finish behavior that the rwsem was providing. This is weaker still than the prior versions: - There is no bias on shortterm_users so if some thread is waiting to destroy other threads can continue to get new read sides - If destruction fails, eg because of an active in-kernel user, then shortterm_users will have cycled to zero momentarily blocking new users - If userspace races destroy with other userspace operations they continue to get an EBUSY since we still can't intermix looking up an ID and sleeping for its unref In all cases these are things that userspace brings on itself, correct programs will not hit them. Fixes: 99f98a7c0d69 ("iommufd: IOMMUFD_DESTROY should not increase the refcount") Link: https://lore.kernel.org/all/2-v2-ca9e00171c5b+123-iommufd_syz4_jgg@nvidia.com/ Reported-by: syzbot+d31adfb277377ef8fcba@syzkaller.appspotmail.com Closes: https://lore.kernel.org/r/00000000000055ef9a0609336580@google.com Reviewed-by: Kevin Tian <kevin.tian@intel.com> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
2023-11-12 15:44:08 -04:00
int iommufd_object_remove(struct iommufd_ctx *ictx,
struct iommufd_object *to_destroy, u32 id,
unsigned int flags)
iommufd: IOMMUFD_DESTROY should not increase the refcount syzkaller found a race where IOMMUFD_DESTROY increments the refcount: obj = iommufd_get_object(ucmd->ictx, cmd->id, IOMMUFD_OBJ_ANY); if (IS_ERR(obj)) return PTR_ERR(obj); iommufd_ref_to_users(obj); /* See iommufd_ref_to_users() */ if (!iommufd_object_destroy_user(ucmd->ictx, obj)) As part of the sequence to join the two existing primitives together. Allowing the refcount the be elevated without holding the destroy_rwsem violates the assumption that all temporary refcount elevations are protected by destroy_rwsem. Racing IOMMUFD_DESTROY with iommufd_object_destroy_user() will cause spurious failures: WARNING: CPU: 0 PID: 3076 at drivers/iommu/iommufd/device.c:477 iommufd_access_destroy+0x18/0x20 drivers/iommu/iommufd/device.c:478 Modules linked in: CPU: 0 PID: 3076 Comm: syz-executor.0 Not tainted 6.3.0-rc1-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/03/2023 RIP: 0010:iommufd_access_destroy+0x18/0x20 drivers/iommu/iommufd/device.c:477 Code: e8 3d 4e 00 00 84 c0 74 01 c3 0f 0b c3 0f 1f 44 00 00 f3 0f 1e fa 48 89 fe 48 8b bf a8 00 00 00 e8 1d 4e 00 00 84 c0 74 01 c3 <0f> 0b c3 0f 1f 44 00 00 41 57 41 56 41 55 4c 8d ae d0 00 00 00 41 RSP: 0018:ffffc90003067e08 EFLAGS: 00010246 RAX: 0000000000000000 RBX: ffff888109ea0300 RCX: 0000000000000000 RDX: 0000000000000001 RSI: 0000000000000000 RDI: 00000000ffffffff RBP: 0000000000000004 R08: 0000000000000000 R09: ffff88810bbb3500 R10: ffff88810bbb3e48 R11: 0000000000000000 R12: ffffc90003067e88 R13: ffffc90003067ea8 R14: ffff888101249800 R15: 00000000fffffffe FS: 00007ff7254fe6c0(0000) GS:ffff888237c00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000555557262da8 CR3: 000000010a6fd000 CR4: 0000000000350ef0 Call Trace: <TASK> iommufd_test_create_access drivers/iommu/iommufd/selftest.c:596 [inline] iommufd_test+0x71c/0xcf0 drivers/iommu/iommufd/selftest.c:813 iommufd_fops_ioctl+0x10f/0x1b0 drivers/iommu/iommufd/main.c:337 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:870 [inline] __se_sys_ioctl fs/ioctl.c:856 [inline] __x64_sys_ioctl+0x84/0xc0 fs/ioctl.c:856 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x38/0x80 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd The solution is to not increment the refcount on the IOMMUFD_DESTROY path at all. Instead use the xa_lock to serialize everything. The refcount check == 1 and xa_erase can be done under a single critical region. This avoids the need for any refcount incrementing. It has the downside that if userspace races destroy with other operations it will get an EBUSY instead of waiting, but this is kind of racing is already dangerous. Fixes: 2ff4bed7fee7 ("iommufd: File descriptor, context, kconfig and makefiles") Link: https://lore.kernel.org/r/2-v1-85aacb2af554+bc-iommufd_syz3_jgg@nvidia.com Reviewed-by: Kevin Tian <kevin.tian@intel.com> Reported-by: syzbot+7574ebfe589049630608@syzkaller.appspotmail.com Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
2023-07-25 16:05:49 -03:00
{
struct iommufd_object *obj;
XA_STATE(xas, &ictx->objects, id);
bool zerod_wait_cnt = false;
iommufd: Do not UAF during iommufd_put_object() The mixture of kernel and user space lifecycle objects continues to be complicated inside iommufd. The obj->destroy_rwsem is used to bring order to the kernel driver destruction sequence but it cannot be sequenced right with the other refcounts so we end up possibly UAF'ing: BUG: KASAN: slab-use-after-free in __up_read+0x627/0x750 kernel/locking/rwsem.c:1342 Read of size 8 at addr ffff888073cde868 by task syz-executor934/6535 CPU: 1 PID: 6535 Comm: syz-executor934 Not tainted 6.6.0-rc7-syzkaller-00195-g2af9b20dbb39 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/09/2023 Call Trace: <TASK> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xd9/0x1b0 lib/dump_stack.c:106 print_address_description mm/kasan/report.c:364 [inline] print_report+0xc4/0x620 mm/kasan/report.c:475 kasan_report+0xda/0x110 mm/kasan/report.c:588 __up_read+0x627/0x750 kernel/locking/rwsem.c:1342 iommufd_put_object drivers/iommu/iommufd/iommufd_private.h:149 [inline] iommufd_vfio_ioas+0x46c/0x580 drivers/iommu/iommufd/vfio_compat.c:146 iommufd_fops_ioctl+0x347/0x4d0 drivers/iommu/iommufd/main.c:398 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:871 [inline] __se_sys_ioctl fs/ioctl.c:857 [inline] __x64_sys_ioctl+0x18f/0x210 fs/ioctl.c:857 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd There are two races here, the more obvious one: CPU 0 CPU 1 iommufd_put_object() iommufd_destroy() refcount_dec(&obj->users) iommufd_object_remove() kfree() up_read(&obj->destroy_rwsem) // Boom And there is also perhaps some possibility that the rwsem could hit an issue: CPU 0 CPU 1 iommufd_put_object() iommufd_object_destroy_user() refcount_dec(&obj->users); down_write(&obj->destroy_rwsem) up_read(&obj->destroy_rwsem); atomic_long_or(RWSEM_FLAG_WAITERS, &sem->count); tmp = atomic_long_add_return_release() rwsem_try_write_lock() iommufd_object_remove() up_write(&obj->destroy_rwsem) kfree() clear_nonspinnable() // Boom Fix this by reorganizing this again so that two refcounts are used to keep track of things with a rule that users == 0 && shortterm_users == 0 means no other threads have that memory. Put a wait_queue in the iommufd_ctx object that is triggered when any sub object reaches a 0 shortterm_users. This allows the same wait for userspace ioctls to finish behavior that the rwsem was providing. This is weaker still than the prior versions: - There is no bias on shortterm_users so if some thread is waiting to destroy other threads can continue to get new read sides - If destruction fails, eg because of an active in-kernel user, then shortterm_users will have cycled to zero momentarily blocking new users - If userspace races destroy with other userspace operations they continue to get an EBUSY since we still can't intermix looking up an ID and sleeping for its unref In all cases these are things that userspace brings on itself, correct programs will not hit them. Fixes: 99f98a7c0d69 ("iommufd: IOMMUFD_DESTROY should not increase the refcount") Link: https://lore.kernel.org/all/2-v2-ca9e00171c5b+123-iommufd_syz4_jgg@nvidia.com/ Reported-by: syzbot+d31adfb277377ef8fcba@syzkaller.appspotmail.com Closes: https://lore.kernel.org/r/00000000000055ef9a0609336580@google.com Reviewed-by: Kevin Tian <kevin.tian@intel.com> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
2023-11-12 15:44:08 -04:00
int ret;
iommufd: IOMMUFD_DESTROY should not increase the refcount syzkaller found a race where IOMMUFD_DESTROY increments the refcount: obj = iommufd_get_object(ucmd->ictx, cmd->id, IOMMUFD_OBJ_ANY); if (IS_ERR(obj)) return PTR_ERR(obj); iommufd_ref_to_users(obj); /* See iommufd_ref_to_users() */ if (!iommufd_object_destroy_user(ucmd->ictx, obj)) As part of the sequence to join the two existing primitives together. Allowing the refcount the be elevated without holding the destroy_rwsem violates the assumption that all temporary refcount elevations are protected by destroy_rwsem. Racing IOMMUFD_DESTROY with iommufd_object_destroy_user() will cause spurious failures: WARNING: CPU: 0 PID: 3076 at drivers/iommu/iommufd/device.c:477 iommufd_access_destroy+0x18/0x20 drivers/iommu/iommufd/device.c:478 Modules linked in: CPU: 0 PID: 3076 Comm: syz-executor.0 Not tainted 6.3.0-rc1-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/03/2023 RIP: 0010:iommufd_access_destroy+0x18/0x20 drivers/iommu/iommufd/device.c:477 Code: e8 3d 4e 00 00 84 c0 74 01 c3 0f 0b c3 0f 1f 44 00 00 f3 0f 1e fa 48 89 fe 48 8b bf a8 00 00 00 e8 1d 4e 00 00 84 c0 74 01 c3 <0f> 0b c3 0f 1f 44 00 00 41 57 41 56 41 55 4c 8d ae d0 00 00 00 41 RSP: 0018:ffffc90003067e08 EFLAGS: 00010246 RAX: 0000000000000000 RBX: ffff888109ea0300 RCX: 0000000000000000 RDX: 0000000000000001 RSI: 0000000000000000 RDI: 00000000ffffffff RBP: 0000000000000004 R08: 0000000000000000 R09: ffff88810bbb3500 R10: ffff88810bbb3e48 R11: 0000000000000000 R12: ffffc90003067e88 R13: ffffc90003067ea8 R14: ffff888101249800 R15: 00000000fffffffe FS: 00007ff7254fe6c0(0000) GS:ffff888237c00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000555557262da8 CR3: 000000010a6fd000 CR4: 0000000000350ef0 Call Trace: <TASK> iommufd_test_create_access drivers/iommu/iommufd/selftest.c:596 [inline] iommufd_test+0x71c/0xcf0 drivers/iommu/iommufd/selftest.c:813 iommufd_fops_ioctl+0x10f/0x1b0 drivers/iommu/iommufd/main.c:337 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:870 [inline] __se_sys_ioctl fs/ioctl.c:856 [inline] __x64_sys_ioctl+0x84/0xc0 fs/ioctl.c:856 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x38/0x80 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd The solution is to not increment the refcount on the IOMMUFD_DESTROY path at all. Instead use the xa_lock to serialize everything. The refcount check == 1 and xa_erase can be done under a single critical region. This avoids the need for any refcount incrementing. It has the downside that if userspace races destroy with other operations it will get an EBUSY instead of waiting, but this is kind of racing is already dangerous. Fixes: 2ff4bed7fee7 ("iommufd: File descriptor, context, kconfig and makefiles") Link: https://lore.kernel.org/r/2-v1-85aacb2af554+bc-iommufd_syz3_jgg@nvidia.com Reviewed-by: Kevin Tian <kevin.tian@intel.com> Reported-by: syzbot+7574ebfe589049630608@syzkaller.appspotmail.com Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
2023-07-25 16:05:49 -03:00
/*
* The purpose of the wait_cnt is to ensure deterministic destruction
* of objects used by external drivers and destroyed by this function.
* Incrementing this wait_cnt should either be short lived, such as
* during ioctl execution, or be revoked and blocked during
* pre_destroy(), such as vdev holding the idev's refcount.
iommufd: IOMMUFD_DESTROY should not increase the refcount syzkaller found a race where IOMMUFD_DESTROY increments the refcount: obj = iommufd_get_object(ucmd->ictx, cmd->id, IOMMUFD_OBJ_ANY); if (IS_ERR(obj)) return PTR_ERR(obj); iommufd_ref_to_users(obj); /* See iommufd_ref_to_users() */ if (!iommufd_object_destroy_user(ucmd->ictx, obj)) As part of the sequence to join the two existing primitives together. Allowing the refcount the be elevated without holding the destroy_rwsem violates the assumption that all temporary refcount elevations are protected by destroy_rwsem. Racing IOMMUFD_DESTROY with iommufd_object_destroy_user() will cause spurious failures: WARNING: CPU: 0 PID: 3076 at drivers/iommu/iommufd/device.c:477 iommufd_access_destroy+0x18/0x20 drivers/iommu/iommufd/device.c:478 Modules linked in: CPU: 0 PID: 3076 Comm: syz-executor.0 Not tainted 6.3.0-rc1-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/03/2023 RIP: 0010:iommufd_access_destroy+0x18/0x20 drivers/iommu/iommufd/device.c:477 Code: e8 3d 4e 00 00 84 c0 74 01 c3 0f 0b c3 0f 1f 44 00 00 f3 0f 1e fa 48 89 fe 48 8b bf a8 00 00 00 e8 1d 4e 00 00 84 c0 74 01 c3 <0f> 0b c3 0f 1f 44 00 00 41 57 41 56 41 55 4c 8d ae d0 00 00 00 41 RSP: 0018:ffffc90003067e08 EFLAGS: 00010246 RAX: 0000000000000000 RBX: ffff888109ea0300 RCX: 0000000000000000 RDX: 0000000000000001 RSI: 0000000000000000 RDI: 00000000ffffffff RBP: 0000000000000004 R08: 0000000000000000 R09: ffff88810bbb3500 R10: ffff88810bbb3e48 R11: 0000000000000000 R12: ffffc90003067e88 R13: ffffc90003067ea8 R14: ffff888101249800 R15: 00000000fffffffe FS: 00007ff7254fe6c0(0000) GS:ffff888237c00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000555557262da8 CR3: 000000010a6fd000 CR4: 0000000000350ef0 Call Trace: <TASK> iommufd_test_create_access drivers/iommu/iommufd/selftest.c:596 [inline] iommufd_test+0x71c/0xcf0 drivers/iommu/iommufd/selftest.c:813 iommufd_fops_ioctl+0x10f/0x1b0 drivers/iommu/iommufd/main.c:337 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:870 [inline] __se_sys_ioctl fs/ioctl.c:856 [inline] __x64_sys_ioctl+0x84/0xc0 fs/ioctl.c:856 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x38/0x80 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd The solution is to not increment the refcount on the IOMMUFD_DESTROY path at all. Instead use the xa_lock to serialize everything. The refcount check == 1 and xa_erase can be done under a single critical region. This avoids the need for any refcount incrementing. It has the downside that if userspace races destroy with other operations it will get an EBUSY instead of waiting, but this is kind of racing is already dangerous. Fixes: 2ff4bed7fee7 ("iommufd: File descriptor, context, kconfig and makefiles") Link: https://lore.kernel.org/r/2-v1-85aacb2af554+bc-iommufd_syz3_jgg@nvidia.com Reviewed-by: Kevin Tian <kevin.tian@intel.com> Reported-by: syzbot+7574ebfe589049630608@syzkaller.appspotmail.com Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
2023-07-25 16:05:49 -03:00
*/
if (flags & REMOVE_WAIT) {
ret = iommufd_object_dec_wait(ictx, to_destroy);
iommufd: Do not UAF during iommufd_put_object() The mixture of kernel and user space lifecycle objects continues to be complicated inside iommufd. The obj->destroy_rwsem is used to bring order to the kernel driver destruction sequence but it cannot be sequenced right with the other refcounts so we end up possibly UAF'ing: BUG: KASAN: slab-use-after-free in __up_read+0x627/0x750 kernel/locking/rwsem.c:1342 Read of size 8 at addr ffff888073cde868 by task syz-executor934/6535 CPU: 1 PID: 6535 Comm: syz-executor934 Not tainted 6.6.0-rc7-syzkaller-00195-g2af9b20dbb39 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/09/2023 Call Trace: <TASK> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xd9/0x1b0 lib/dump_stack.c:106 print_address_description mm/kasan/report.c:364 [inline] print_report+0xc4/0x620 mm/kasan/report.c:475 kasan_report+0xda/0x110 mm/kasan/report.c:588 __up_read+0x627/0x750 kernel/locking/rwsem.c:1342 iommufd_put_object drivers/iommu/iommufd/iommufd_private.h:149 [inline] iommufd_vfio_ioas+0x46c/0x580 drivers/iommu/iommufd/vfio_compat.c:146 iommufd_fops_ioctl+0x347/0x4d0 drivers/iommu/iommufd/main.c:398 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:871 [inline] __se_sys_ioctl fs/ioctl.c:857 [inline] __x64_sys_ioctl+0x18f/0x210 fs/ioctl.c:857 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd There are two races here, the more obvious one: CPU 0 CPU 1 iommufd_put_object() iommufd_destroy() refcount_dec(&obj->users) iommufd_object_remove() kfree() up_read(&obj->destroy_rwsem) // Boom And there is also perhaps some possibility that the rwsem could hit an issue: CPU 0 CPU 1 iommufd_put_object() iommufd_object_destroy_user() refcount_dec(&obj->users); down_write(&obj->destroy_rwsem) up_read(&obj->destroy_rwsem); atomic_long_or(RWSEM_FLAG_WAITERS, &sem->count); tmp = atomic_long_add_return_release() rwsem_try_write_lock() iommufd_object_remove() up_write(&obj->destroy_rwsem) kfree() clear_nonspinnable() // Boom Fix this by reorganizing this again so that two refcounts are used to keep track of things with a rule that users == 0 && shortterm_users == 0 means no other threads have that memory. Put a wait_queue in the iommufd_ctx object that is triggered when any sub object reaches a 0 shortterm_users. This allows the same wait for userspace ioctls to finish behavior that the rwsem was providing. This is weaker still than the prior versions: - There is no bias on shortterm_users so if some thread is waiting to destroy other threads can continue to get new read sides - If destruction fails, eg because of an active in-kernel user, then shortterm_users will have cycled to zero momentarily blocking new users - If userspace races destroy with other userspace operations they continue to get an EBUSY since we still can't intermix looking up an ID and sleeping for its unref In all cases these are things that userspace brings on itself, correct programs will not hit them. Fixes: 99f98a7c0d69 ("iommufd: IOMMUFD_DESTROY should not increase the refcount") Link: https://lore.kernel.org/all/2-v2-ca9e00171c5b+123-iommufd_syz4_jgg@nvidia.com/ Reported-by: syzbot+d31adfb277377ef8fcba@syzkaller.appspotmail.com Closes: https://lore.kernel.org/r/00000000000055ef9a0609336580@google.com Reviewed-by: Kevin Tian <kevin.tian@intel.com> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
2023-11-12 15:44:08 -04:00
if (ret) {
/*
* We have a bug. Put back the callers reference and
* defer cleaning this object until close.
*/
refcount_dec(&to_destroy->users);
return ret;
}
zerod_wait_cnt = true;
iommufd: Do not UAF during iommufd_put_object() The mixture of kernel and user space lifecycle objects continues to be complicated inside iommufd. The obj->destroy_rwsem is used to bring order to the kernel driver destruction sequence but it cannot be sequenced right with the other refcounts so we end up possibly UAF'ing: BUG: KASAN: slab-use-after-free in __up_read+0x627/0x750 kernel/locking/rwsem.c:1342 Read of size 8 at addr ffff888073cde868 by task syz-executor934/6535 CPU: 1 PID: 6535 Comm: syz-executor934 Not tainted 6.6.0-rc7-syzkaller-00195-g2af9b20dbb39 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/09/2023 Call Trace: <TASK> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xd9/0x1b0 lib/dump_stack.c:106 print_address_description mm/kasan/report.c:364 [inline] print_report+0xc4/0x620 mm/kasan/report.c:475 kasan_report+0xda/0x110 mm/kasan/report.c:588 __up_read+0x627/0x750 kernel/locking/rwsem.c:1342 iommufd_put_object drivers/iommu/iommufd/iommufd_private.h:149 [inline] iommufd_vfio_ioas+0x46c/0x580 drivers/iommu/iommufd/vfio_compat.c:146 iommufd_fops_ioctl+0x347/0x4d0 drivers/iommu/iommufd/main.c:398 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:871 [inline] __se_sys_ioctl fs/ioctl.c:857 [inline] __x64_sys_ioctl+0x18f/0x210 fs/ioctl.c:857 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd There are two races here, the more obvious one: CPU 0 CPU 1 iommufd_put_object() iommufd_destroy() refcount_dec(&obj->users) iommufd_object_remove() kfree() up_read(&obj->destroy_rwsem) // Boom And there is also perhaps some possibility that the rwsem could hit an issue: CPU 0 CPU 1 iommufd_put_object() iommufd_object_destroy_user() refcount_dec(&obj->users); down_write(&obj->destroy_rwsem) up_read(&obj->destroy_rwsem); atomic_long_or(RWSEM_FLAG_WAITERS, &sem->count); tmp = atomic_long_add_return_release() rwsem_try_write_lock() iommufd_object_remove() up_write(&obj->destroy_rwsem) kfree() clear_nonspinnable() // Boom Fix this by reorganizing this again so that two refcounts are used to keep track of things with a rule that users == 0 && shortterm_users == 0 means no other threads have that memory. Put a wait_queue in the iommufd_ctx object that is triggered when any sub object reaches a 0 shortterm_users. This allows the same wait for userspace ioctls to finish behavior that the rwsem was providing. This is weaker still than the prior versions: - There is no bias on shortterm_users so if some thread is waiting to destroy other threads can continue to get new read sides - If destruction fails, eg because of an active in-kernel user, then shortterm_users will have cycled to zero momentarily blocking new users - If userspace races destroy with other userspace operations they continue to get an EBUSY since we still can't intermix looking up an ID and sleeping for its unref In all cases these are things that userspace brings on itself, correct programs will not hit them. Fixes: 99f98a7c0d69 ("iommufd: IOMMUFD_DESTROY should not increase the refcount") Link: https://lore.kernel.org/all/2-v2-ca9e00171c5b+123-iommufd_syz4_jgg@nvidia.com/ Reported-by: syzbot+d31adfb277377ef8fcba@syzkaller.appspotmail.com Closes: https://lore.kernel.org/r/00000000000055ef9a0609336580@google.com Reviewed-by: Kevin Tian <kevin.tian@intel.com> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
2023-11-12 15:44:08 -04:00
}
xa_lock(&ictx->objects);
obj = xas_load(&xas);
if (to_destroy) {
/*
* If the caller is holding a ref on obj we put it here under
* the spinlock.
*/
iommufd: IOMMUFD_DESTROY should not increase the refcount syzkaller found a race where IOMMUFD_DESTROY increments the refcount: obj = iommufd_get_object(ucmd->ictx, cmd->id, IOMMUFD_OBJ_ANY); if (IS_ERR(obj)) return PTR_ERR(obj); iommufd_ref_to_users(obj); /* See iommufd_ref_to_users() */ if (!iommufd_object_destroy_user(ucmd->ictx, obj)) As part of the sequence to join the two existing primitives together. Allowing the refcount the be elevated without holding the destroy_rwsem violates the assumption that all temporary refcount elevations are protected by destroy_rwsem. Racing IOMMUFD_DESTROY with iommufd_object_destroy_user() will cause spurious failures: WARNING: CPU: 0 PID: 3076 at drivers/iommu/iommufd/device.c:477 iommufd_access_destroy+0x18/0x20 drivers/iommu/iommufd/device.c:478 Modules linked in: CPU: 0 PID: 3076 Comm: syz-executor.0 Not tainted 6.3.0-rc1-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/03/2023 RIP: 0010:iommufd_access_destroy+0x18/0x20 drivers/iommu/iommufd/device.c:477 Code: e8 3d 4e 00 00 84 c0 74 01 c3 0f 0b c3 0f 1f 44 00 00 f3 0f 1e fa 48 89 fe 48 8b bf a8 00 00 00 e8 1d 4e 00 00 84 c0 74 01 c3 <0f> 0b c3 0f 1f 44 00 00 41 57 41 56 41 55 4c 8d ae d0 00 00 00 41 RSP: 0018:ffffc90003067e08 EFLAGS: 00010246 RAX: 0000000000000000 RBX: ffff888109ea0300 RCX: 0000000000000000 RDX: 0000000000000001 RSI: 0000000000000000 RDI: 00000000ffffffff RBP: 0000000000000004 R08: 0000000000000000 R09: ffff88810bbb3500 R10: ffff88810bbb3e48 R11: 0000000000000000 R12: ffffc90003067e88 R13: ffffc90003067ea8 R14: ffff888101249800 R15: 00000000fffffffe FS: 00007ff7254fe6c0(0000) GS:ffff888237c00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000555557262da8 CR3: 000000010a6fd000 CR4: 0000000000350ef0 Call Trace: <TASK> iommufd_test_create_access drivers/iommu/iommufd/selftest.c:596 [inline] iommufd_test+0x71c/0xcf0 drivers/iommu/iommufd/selftest.c:813 iommufd_fops_ioctl+0x10f/0x1b0 drivers/iommu/iommufd/main.c:337 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:870 [inline] __se_sys_ioctl fs/ioctl.c:856 [inline] __x64_sys_ioctl+0x84/0xc0 fs/ioctl.c:856 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x38/0x80 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd The solution is to not increment the refcount on the IOMMUFD_DESTROY path at all. Instead use the xa_lock to serialize everything. The refcount check == 1 and xa_erase can be done under a single critical region. This avoids the need for any refcount incrementing. It has the downside that if userspace races destroy with other operations it will get an EBUSY instead of waiting, but this is kind of racing is already dangerous. Fixes: 2ff4bed7fee7 ("iommufd: File descriptor, context, kconfig and makefiles") Link: https://lore.kernel.org/r/2-v1-85aacb2af554+bc-iommufd_syz3_jgg@nvidia.com Reviewed-by: Kevin Tian <kevin.tian@intel.com> Reported-by: syzbot+7574ebfe589049630608@syzkaller.appspotmail.com Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
2023-07-25 16:05:49 -03:00
refcount_dec(&obj->users);
iommufd: Do not UAF during iommufd_put_object() The mixture of kernel and user space lifecycle objects continues to be complicated inside iommufd. The obj->destroy_rwsem is used to bring order to the kernel driver destruction sequence but it cannot be sequenced right with the other refcounts so we end up possibly UAF'ing: BUG: KASAN: slab-use-after-free in __up_read+0x627/0x750 kernel/locking/rwsem.c:1342 Read of size 8 at addr ffff888073cde868 by task syz-executor934/6535 CPU: 1 PID: 6535 Comm: syz-executor934 Not tainted 6.6.0-rc7-syzkaller-00195-g2af9b20dbb39 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/09/2023 Call Trace: <TASK> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xd9/0x1b0 lib/dump_stack.c:106 print_address_description mm/kasan/report.c:364 [inline] print_report+0xc4/0x620 mm/kasan/report.c:475 kasan_report+0xda/0x110 mm/kasan/report.c:588 __up_read+0x627/0x750 kernel/locking/rwsem.c:1342 iommufd_put_object drivers/iommu/iommufd/iommufd_private.h:149 [inline] iommufd_vfio_ioas+0x46c/0x580 drivers/iommu/iommufd/vfio_compat.c:146 iommufd_fops_ioctl+0x347/0x4d0 drivers/iommu/iommufd/main.c:398 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:871 [inline] __se_sys_ioctl fs/ioctl.c:857 [inline] __x64_sys_ioctl+0x18f/0x210 fs/ioctl.c:857 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd There are two races here, the more obvious one: CPU 0 CPU 1 iommufd_put_object() iommufd_destroy() refcount_dec(&obj->users) iommufd_object_remove() kfree() up_read(&obj->destroy_rwsem) // Boom And there is also perhaps some possibility that the rwsem could hit an issue: CPU 0 CPU 1 iommufd_put_object() iommufd_object_destroy_user() refcount_dec(&obj->users); down_write(&obj->destroy_rwsem) up_read(&obj->destroy_rwsem); atomic_long_or(RWSEM_FLAG_WAITERS, &sem->count); tmp = atomic_long_add_return_release() rwsem_try_write_lock() iommufd_object_remove() up_write(&obj->destroy_rwsem) kfree() clear_nonspinnable() // Boom Fix this by reorganizing this again so that two refcounts are used to keep track of things with a rule that users == 0 && shortterm_users == 0 means no other threads have that memory. Put a wait_queue in the iommufd_ctx object that is triggered when any sub object reaches a 0 shortterm_users. This allows the same wait for userspace ioctls to finish behavior that the rwsem was providing. This is weaker still than the prior versions: - There is no bias on shortterm_users so if some thread is waiting to destroy other threads can continue to get new read sides - If destruction fails, eg because of an active in-kernel user, then shortterm_users will have cycled to zero momentarily blocking new users - If userspace races destroy with other userspace operations they continue to get an EBUSY since we still can't intermix looking up an ID and sleeping for its unref In all cases these are things that userspace brings on itself, correct programs will not hit them. Fixes: 99f98a7c0d69 ("iommufd: IOMMUFD_DESTROY should not increase the refcount") Link: https://lore.kernel.org/all/2-v2-ca9e00171c5b+123-iommufd_syz4_jgg@nvidia.com/ Reported-by: syzbot+d31adfb277377ef8fcba@syzkaller.appspotmail.com Closes: https://lore.kernel.org/r/00000000000055ef9a0609336580@google.com Reviewed-by: Kevin Tian <kevin.tian@intel.com> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
2023-11-12 15:44:08 -04:00
if (WARN_ON(obj != to_destroy)) {
ret = -ENOENT;
goto err_xa;
}
} else if (xa_is_zero(obj) || !obj) {
ret = -ENOENT;
goto err_xa;
}
iommufd: IOMMUFD_DESTROY should not increase the refcount syzkaller found a race where IOMMUFD_DESTROY increments the refcount: obj = iommufd_get_object(ucmd->ictx, cmd->id, IOMMUFD_OBJ_ANY); if (IS_ERR(obj)) return PTR_ERR(obj); iommufd_ref_to_users(obj); /* See iommufd_ref_to_users() */ if (!iommufd_object_destroy_user(ucmd->ictx, obj)) As part of the sequence to join the two existing primitives together. Allowing the refcount the be elevated without holding the destroy_rwsem violates the assumption that all temporary refcount elevations are protected by destroy_rwsem. Racing IOMMUFD_DESTROY with iommufd_object_destroy_user() will cause spurious failures: WARNING: CPU: 0 PID: 3076 at drivers/iommu/iommufd/device.c:477 iommufd_access_destroy+0x18/0x20 drivers/iommu/iommufd/device.c:478 Modules linked in: CPU: 0 PID: 3076 Comm: syz-executor.0 Not tainted 6.3.0-rc1-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/03/2023 RIP: 0010:iommufd_access_destroy+0x18/0x20 drivers/iommu/iommufd/device.c:477 Code: e8 3d 4e 00 00 84 c0 74 01 c3 0f 0b c3 0f 1f 44 00 00 f3 0f 1e fa 48 89 fe 48 8b bf a8 00 00 00 e8 1d 4e 00 00 84 c0 74 01 c3 <0f> 0b c3 0f 1f 44 00 00 41 57 41 56 41 55 4c 8d ae d0 00 00 00 41 RSP: 0018:ffffc90003067e08 EFLAGS: 00010246 RAX: 0000000000000000 RBX: ffff888109ea0300 RCX: 0000000000000000 RDX: 0000000000000001 RSI: 0000000000000000 RDI: 00000000ffffffff RBP: 0000000000000004 R08: 0000000000000000 R09: ffff88810bbb3500 R10: ffff88810bbb3e48 R11: 0000000000000000 R12: ffffc90003067e88 R13: ffffc90003067ea8 R14: ffff888101249800 R15: 00000000fffffffe FS: 00007ff7254fe6c0(0000) GS:ffff888237c00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000555557262da8 CR3: 000000010a6fd000 CR4: 0000000000350ef0 Call Trace: <TASK> iommufd_test_create_access drivers/iommu/iommufd/selftest.c:596 [inline] iommufd_test+0x71c/0xcf0 drivers/iommu/iommufd/selftest.c:813 iommufd_fops_ioctl+0x10f/0x1b0 drivers/iommu/iommufd/main.c:337 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:870 [inline] __se_sys_ioctl fs/ioctl.c:856 [inline] __x64_sys_ioctl+0x84/0xc0 fs/ioctl.c:856 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x38/0x80 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd The solution is to not increment the refcount on the IOMMUFD_DESTROY path at all. Instead use the xa_lock to serialize everything. The refcount check == 1 and xa_erase can be done under a single critical region. This avoids the need for any refcount incrementing. It has the downside that if userspace races destroy with other operations it will get an EBUSY instead of waiting, but this is kind of racing is already dangerous. Fixes: 2ff4bed7fee7 ("iommufd: File descriptor, context, kconfig and makefiles") Link: https://lore.kernel.org/r/2-v1-85aacb2af554+bc-iommufd_syz3_jgg@nvidia.com Reviewed-by: Kevin Tian <kevin.tian@intel.com> Reported-by: syzbot+7574ebfe589049630608@syzkaller.appspotmail.com Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
2023-07-25 16:05:49 -03:00
if (!refcount_dec_if_one(&obj->users)) {
iommufd: Do not UAF during iommufd_put_object() The mixture of kernel and user space lifecycle objects continues to be complicated inside iommufd. The obj->destroy_rwsem is used to bring order to the kernel driver destruction sequence but it cannot be sequenced right with the other refcounts so we end up possibly UAF'ing: BUG: KASAN: slab-use-after-free in __up_read+0x627/0x750 kernel/locking/rwsem.c:1342 Read of size 8 at addr ffff888073cde868 by task syz-executor934/6535 CPU: 1 PID: 6535 Comm: syz-executor934 Not tainted 6.6.0-rc7-syzkaller-00195-g2af9b20dbb39 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/09/2023 Call Trace: <TASK> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xd9/0x1b0 lib/dump_stack.c:106 print_address_description mm/kasan/report.c:364 [inline] print_report+0xc4/0x620 mm/kasan/report.c:475 kasan_report+0xda/0x110 mm/kasan/report.c:588 __up_read+0x627/0x750 kernel/locking/rwsem.c:1342 iommufd_put_object drivers/iommu/iommufd/iommufd_private.h:149 [inline] iommufd_vfio_ioas+0x46c/0x580 drivers/iommu/iommufd/vfio_compat.c:146 iommufd_fops_ioctl+0x347/0x4d0 drivers/iommu/iommufd/main.c:398 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:871 [inline] __se_sys_ioctl fs/ioctl.c:857 [inline] __x64_sys_ioctl+0x18f/0x210 fs/ioctl.c:857 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd There are two races here, the more obvious one: CPU 0 CPU 1 iommufd_put_object() iommufd_destroy() refcount_dec(&obj->users) iommufd_object_remove() kfree() up_read(&obj->destroy_rwsem) // Boom And there is also perhaps some possibility that the rwsem could hit an issue: CPU 0 CPU 1 iommufd_put_object() iommufd_object_destroy_user() refcount_dec(&obj->users); down_write(&obj->destroy_rwsem) up_read(&obj->destroy_rwsem); atomic_long_or(RWSEM_FLAG_WAITERS, &sem->count); tmp = atomic_long_add_return_release() rwsem_try_write_lock() iommufd_object_remove() up_write(&obj->destroy_rwsem) kfree() clear_nonspinnable() // Boom Fix this by reorganizing this again so that two refcounts are used to keep track of things with a rule that users == 0 && shortterm_users == 0 means no other threads have that memory. Put a wait_queue in the iommufd_ctx object that is triggered when any sub object reaches a 0 shortterm_users. This allows the same wait for userspace ioctls to finish behavior that the rwsem was providing. This is weaker still than the prior versions: - There is no bias on shortterm_users so if some thread is waiting to destroy other threads can continue to get new read sides - If destruction fails, eg because of an active in-kernel user, then shortterm_users will have cycled to zero momentarily blocking new users - If userspace races destroy with other userspace operations they continue to get an EBUSY since we still can't intermix looking up an ID and sleeping for its unref In all cases these are things that userspace brings on itself, correct programs will not hit them. Fixes: 99f98a7c0d69 ("iommufd: IOMMUFD_DESTROY should not increase the refcount") Link: https://lore.kernel.org/all/2-v2-ca9e00171c5b+123-iommufd_syz4_jgg@nvidia.com/ Reported-by: syzbot+d31adfb277377ef8fcba@syzkaller.appspotmail.com Closes: https://lore.kernel.org/r/00000000000055ef9a0609336580@google.com Reviewed-by: Kevin Tian <kevin.tian@intel.com> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
2023-11-12 15:44:08 -04:00
ret = -EBUSY;
goto err_xa;
iommufd: IOMMUFD_DESTROY should not increase the refcount syzkaller found a race where IOMMUFD_DESTROY increments the refcount: obj = iommufd_get_object(ucmd->ictx, cmd->id, IOMMUFD_OBJ_ANY); if (IS_ERR(obj)) return PTR_ERR(obj); iommufd_ref_to_users(obj); /* See iommufd_ref_to_users() */ if (!iommufd_object_destroy_user(ucmd->ictx, obj)) As part of the sequence to join the two existing primitives together. Allowing the refcount the be elevated without holding the destroy_rwsem violates the assumption that all temporary refcount elevations are protected by destroy_rwsem. Racing IOMMUFD_DESTROY with iommufd_object_destroy_user() will cause spurious failures: WARNING: CPU: 0 PID: 3076 at drivers/iommu/iommufd/device.c:477 iommufd_access_destroy+0x18/0x20 drivers/iommu/iommufd/device.c:478 Modules linked in: CPU: 0 PID: 3076 Comm: syz-executor.0 Not tainted 6.3.0-rc1-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/03/2023 RIP: 0010:iommufd_access_destroy+0x18/0x20 drivers/iommu/iommufd/device.c:477 Code: e8 3d 4e 00 00 84 c0 74 01 c3 0f 0b c3 0f 1f 44 00 00 f3 0f 1e fa 48 89 fe 48 8b bf a8 00 00 00 e8 1d 4e 00 00 84 c0 74 01 c3 <0f> 0b c3 0f 1f 44 00 00 41 57 41 56 41 55 4c 8d ae d0 00 00 00 41 RSP: 0018:ffffc90003067e08 EFLAGS: 00010246 RAX: 0000000000000000 RBX: ffff888109ea0300 RCX: 0000000000000000 RDX: 0000000000000001 RSI: 0000000000000000 RDI: 00000000ffffffff RBP: 0000000000000004 R08: 0000000000000000 R09: ffff88810bbb3500 R10: ffff88810bbb3e48 R11: 0000000000000000 R12: ffffc90003067e88 R13: ffffc90003067ea8 R14: ffff888101249800 R15: 00000000fffffffe FS: 00007ff7254fe6c0(0000) GS:ffff888237c00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000555557262da8 CR3: 000000010a6fd000 CR4: 0000000000350ef0 Call Trace: <TASK> iommufd_test_create_access drivers/iommu/iommufd/selftest.c:596 [inline] iommufd_test+0x71c/0xcf0 drivers/iommu/iommufd/selftest.c:813 iommufd_fops_ioctl+0x10f/0x1b0 drivers/iommu/iommufd/main.c:337 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:870 [inline] __se_sys_ioctl fs/ioctl.c:856 [inline] __x64_sys_ioctl+0x84/0xc0 fs/ioctl.c:856 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x38/0x80 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd The solution is to not increment the refcount on the IOMMUFD_DESTROY path at all. Instead use the xa_lock to serialize everything. The refcount check == 1 and xa_erase can be done under a single critical region. This avoids the need for any refcount incrementing. It has the downside that if userspace races destroy with other operations it will get an EBUSY instead of waiting, but this is kind of racing is already dangerous. Fixes: 2ff4bed7fee7 ("iommufd: File descriptor, context, kconfig and makefiles") Link: https://lore.kernel.org/r/2-v1-85aacb2af554+bc-iommufd_syz3_jgg@nvidia.com Reviewed-by: Kevin Tian <kevin.tian@intel.com> Reported-by: syzbot+7574ebfe589049630608@syzkaller.appspotmail.com Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
2023-07-25 16:05:49 -03:00
}
xas_store(&xas, (flags & REMOVE_OBJ_TOMBSTONE) ? XA_ZERO_ENTRY : NULL);
iommufd: IOMMUFD_DESTROY should not increase the refcount syzkaller found a race where IOMMUFD_DESTROY increments the refcount: obj = iommufd_get_object(ucmd->ictx, cmd->id, IOMMUFD_OBJ_ANY); if (IS_ERR(obj)) return PTR_ERR(obj); iommufd_ref_to_users(obj); /* See iommufd_ref_to_users() */ if (!iommufd_object_destroy_user(ucmd->ictx, obj)) As part of the sequence to join the two existing primitives together. Allowing the refcount the be elevated without holding the destroy_rwsem violates the assumption that all temporary refcount elevations are protected by destroy_rwsem. Racing IOMMUFD_DESTROY with iommufd_object_destroy_user() will cause spurious failures: WARNING: CPU: 0 PID: 3076 at drivers/iommu/iommufd/device.c:477 iommufd_access_destroy+0x18/0x20 drivers/iommu/iommufd/device.c:478 Modules linked in: CPU: 0 PID: 3076 Comm: syz-executor.0 Not tainted 6.3.0-rc1-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/03/2023 RIP: 0010:iommufd_access_destroy+0x18/0x20 drivers/iommu/iommufd/device.c:477 Code: e8 3d 4e 00 00 84 c0 74 01 c3 0f 0b c3 0f 1f 44 00 00 f3 0f 1e fa 48 89 fe 48 8b bf a8 00 00 00 e8 1d 4e 00 00 84 c0 74 01 c3 <0f> 0b c3 0f 1f 44 00 00 41 57 41 56 41 55 4c 8d ae d0 00 00 00 41 RSP: 0018:ffffc90003067e08 EFLAGS: 00010246 RAX: 0000000000000000 RBX: ffff888109ea0300 RCX: 0000000000000000 RDX: 0000000000000001 RSI: 0000000000000000 RDI: 00000000ffffffff RBP: 0000000000000004 R08: 0000000000000000 R09: ffff88810bbb3500 R10: ffff88810bbb3e48 R11: 0000000000000000 R12: ffffc90003067e88 R13: ffffc90003067ea8 R14: ffff888101249800 R15: 00000000fffffffe FS: 00007ff7254fe6c0(0000) GS:ffff888237c00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000555557262da8 CR3: 000000010a6fd000 CR4: 0000000000350ef0 Call Trace: <TASK> iommufd_test_create_access drivers/iommu/iommufd/selftest.c:596 [inline] iommufd_test+0x71c/0xcf0 drivers/iommu/iommufd/selftest.c:813 iommufd_fops_ioctl+0x10f/0x1b0 drivers/iommu/iommufd/main.c:337 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:870 [inline] __se_sys_ioctl fs/ioctl.c:856 [inline] __x64_sys_ioctl+0x84/0xc0 fs/ioctl.c:856 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x38/0x80 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd The solution is to not increment the refcount on the IOMMUFD_DESTROY path at all. Instead use the xa_lock to serialize everything. The refcount check == 1 and xa_erase can be done under a single critical region. This avoids the need for any refcount incrementing. It has the downside that if userspace races destroy with other operations it will get an EBUSY instead of waiting, but this is kind of racing is already dangerous. Fixes: 2ff4bed7fee7 ("iommufd: File descriptor, context, kconfig and makefiles") Link: https://lore.kernel.org/r/2-v1-85aacb2af554+bc-iommufd_syz3_jgg@nvidia.com Reviewed-by: Kevin Tian <kevin.tian@intel.com> Reported-by: syzbot+7574ebfe589049630608@syzkaller.appspotmail.com Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
2023-07-25 16:05:49 -03:00
if (ictx->vfio_ioas == container_of(obj, struct iommufd_ioas, obj))
ictx->vfio_ioas = NULL;
xa_unlock(&ictx->objects);
/*
* Since users is zero any positive wait_cnt must be racing
iommufd: Do not UAF during iommufd_put_object() The mixture of kernel and user space lifecycle objects continues to be complicated inside iommufd. The obj->destroy_rwsem is used to bring order to the kernel driver destruction sequence but it cannot be sequenced right with the other refcounts so we end up possibly UAF'ing: BUG: KASAN: slab-use-after-free in __up_read+0x627/0x750 kernel/locking/rwsem.c:1342 Read of size 8 at addr ffff888073cde868 by task syz-executor934/6535 CPU: 1 PID: 6535 Comm: syz-executor934 Not tainted 6.6.0-rc7-syzkaller-00195-g2af9b20dbb39 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/09/2023 Call Trace: <TASK> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xd9/0x1b0 lib/dump_stack.c:106 print_address_description mm/kasan/report.c:364 [inline] print_report+0xc4/0x620 mm/kasan/report.c:475 kasan_report+0xda/0x110 mm/kasan/report.c:588 __up_read+0x627/0x750 kernel/locking/rwsem.c:1342 iommufd_put_object drivers/iommu/iommufd/iommufd_private.h:149 [inline] iommufd_vfio_ioas+0x46c/0x580 drivers/iommu/iommufd/vfio_compat.c:146 iommufd_fops_ioctl+0x347/0x4d0 drivers/iommu/iommufd/main.c:398 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:871 [inline] __se_sys_ioctl fs/ioctl.c:857 [inline] __x64_sys_ioctl+0x18f/0x210 fs/ioctl.c:857 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd There are two races here, the more obvious one: CPU 0 CPU 1 iommufd_put_object() iommufd_destroy() refcount_dec(&obj->users) iommufd_object_remove() kfree() up_read(&obj->destroy_rwsem) // Boom And there is also perhaps some possibility that the rwsem could hit an issue: CPU 0 CPU 1 iommufd_put_object() iommufd_object_destroy_user() refcount_dec(&obj->users); down_write(&obj->destroy_rwsem) up_read(&obj->destroy_rwsem); atomic_long_or(RWSEM_FLAG_WAITERS, &sem->count); tmp = atomic_long_add_return_release() rwsem_try_write_lock() iommufd_object_remove() up_write(&obj->destroy_rwsem) kfree() clear_nonspinnable() // Boom Fix this by reorganizing this again so that two refcounts are used to keep track of things with a rule that users == 0 && shortterm_users == 0 means no other threads have that memory. Put a wait_queue in the iommufd_ctx object that is triggered when any sub object reaches a 0 shortterm_users. This allows the same wait for userspace ioctls to finish behavior that the rwsem was providing. This is weaker still than the prior versions: - There is no bias on shortterm_users so if some thread is waiting to destroy other threads can continue to get new read sides - If destruction fails, eg because of an active in-kernel user, then shortterm_users will have cycled to zero momentarily blocking new users - If userspace races destroy with other userspace operations they continue to get an EBUSY since we still can't intermix looking up an ID and sleeping for its unref In all cases these are things that userspace brings on itself, correct programs will not hit them. Fixes: 99f98a7c0d69 ("iommufd: IOMMUFD_DESTROY should not increase the refcount") Link: https://lore.kernel.org/all/2-v2-ca9e00171c5b+123-iommufd_syz4_jgg@nvidia.com/ Reported-by: syzbot+d31adfb277377ef8fcba@syzkaller.appspotmail.com Closes: https://lore.kernel.org/r/00000000000055ef9a0609336580@google.com Reviewed-by: Kevin Tian <kevin.tian@intel.com> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
2023-11-12 15:44:08 -04:00
* iommufd_put_object(), or we have a bug.
*/
if (!zerod_wait_cnt) {
ret = iommufd_object_dec_wait(ictx, obj);
iommufd: Do not UAF during iommufd_put_object() The mixture of kernel and user space lifecycle objects continues to be complicated inside iommufd. The obj->destroy_rwsem is used to bring order to the kernel driver destruction sequence but it cannot be sequenced right with the other refcounts so we end up possibly UAF'ing: BUG: KASAN: slab-use-after-free in __up_read+0x627/0x750 kernel/locking/rwsem.c:1342 Read of size 8 at addr ffff888073cde868 by task syz-executor934/6535 CPU: 1 PID: 6535 Comm: syz-executor934 Not tainted 6.6.0-rc7-syzkaller-00195-g2af9b20dbb39 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/09/2023 Call Trace: <TASK> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xd9/0x1b0 lib/dump_stack.c:106 print_address_description mm/kasan/report.c:364 [inline] print_report+0xc4/0x620 mm/kasan/report.c:475 kasan_report+0xda/0x110 mm/kasan/report.c:588 __up_read+0x627/0x750 kernel/locking/rwsem.c:1342 iommufd_put_object drivers/iommu/iommufd/iommufd_private.h:149 [inline] iommufd_vfio_ioas+0x46c/0x580 drivers/iommu/iommufd/vfio_compat.c:146 iommufd_fops_ioctl+0x347/0x4d0 drivers/iommu/iommufd/main.c:398 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:871 [inline] __se_sys_ioctl fs/ioctl.c:857 [inline] __x64_sys_ioctl+0x18f/0x210 fs/ioctl.c:857 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd There are two races here, the more obvious one: CPU 0 CPU 1 iommufd_put_object() iommufd_destroy() refcount_dec(&obj->users) iommufd_object_remove() kfree() up_read(&obj->destroy_rwsem) // Boom And there is also perhaps some possibility that the rwsem could hit an issue: CPU 0 CPU 1 iommufd_put_object() iommufd_object_destroy_user() refcount_dec(&obj->users); down_write(&obj->destroy_rwsem) up_read(&obj->destroy_rwsem); atomic_long_or(RWSEM_FLAG_WAITERS, &sem->count); tmp = atomic_long_add_return_release() rwsem_try_write_lock() iommufd_object_remove() up_write(&obj->destroy_rwsem) kfree() clear_nonspinnable() // Boom Fix this by reorganizing this again so that two refcounts are used to keep track of things with a rule that users == 0 && shortterm_users == 0 means no other threads have that memory. Put a wait_queue in the iommufd_ctx object that is triggered when any sub object reaches a 0 shortterm_users. This allows the same wait for userspace ioctls to finish behavior that the rwsem was providing. This is weaker still than the prior versions: - There is no bias on shortterm_users so if some thread is waiting to destroy other threads can continue to get new read sides - If destruction fails, eg because of an active in-kernel user, then shortterm_users will have cycled to zero momentarily blocking new users - If userspace races destroy with other userspace operations they continue to get an EBUSY since we still can't intermix looking up an ID and sleeping for its unref In all cases these are things that userspace brings on itself, correct programs will not hit them. Fixes: 99f98a7c0d69 ("iommufd: IOMMUFD_DESTROY should not increase the refcount") Link: https://lore.kernel.org/all/2-v2-ca9e00171c5b+123-iommufd_syz4_jgg@nvidia.com/ Reported-by: syzbot+d31adfb277377ef8fcba@syzkaller.appspotmail.com Closes: https://lore.kernel.org/r/00000000000055ef9a0609336580@google.com Reviewed-by: Kevin Tian <kevin.tian@intel.com> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
2023-11-12 15:44:08 -04:00
if (WARN_ON(ret))
return ret;
}
iommufd: IOMMUFD_DESTROY should not increase the refcount syzkaller found a race where IOMMUFD_DESTROY increments the refcount: obj = iommufd_get_object(ucmd->ictx, cmd->id, IOMMUFD_OBJ_ANY); if (IS_ERR(obj)) return PTR_ERR(obj); iommufd_ref_to_users(obj); /* See iommufd_ref_to_users() */ if (!iommufd_object_destroy_user(ucmd->ictx, obj)) As part of the sequence to join the two existing primitives together. Allowing the refcount the be elevated without holding the destroy_rwsem violates the assumption that all temporary refcount elevations are protected by destroy_rwsem. Racing IOMMUFD_DESTROY with iommufd_object_destroy_user() will cause spurious failures: WARNING: CPU: 0 PID: 3076 at drivers/iommu/iommufd/device.c:477 iommufd_access_destroy+0x18/0x20 drivers/iommu/iommufd/device.c:478 Modules linked in: CPU: 0 PID: 3076 Comm: syz-executor.0 Not tainted 6.3.0-rc1-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/03/2023 RIP: 0010:iommufd_access_destroy+0x18/0x20 drivers/iommu/iommufd/device.c:477 Code: e8 3d 4e 00 00 84 c0 74 01 c3 0f 0b c3 0f 1f 44 00 00 f3 0f 1e fa 48 89 fe 48 8b bf a8 00 00 00 e8 1d 4e 00 00 84 c0 74 01 c3 <0f> 0b c3 0f 1f 44 00 00 41 57 41 56 41 55 4c 8d ae d0 00 00 00 41 RSP: 0018:ffffc90003067e08 EFLAGS: 00010246 RAX: 0000000000000000 RBX: ffff888109ea0300 RCX: 0000000000000000 RDX: 0000000000000001 RSI: 0000000000000000 RDI: 00000000ffffffff RBP: 0000000000000004 R08: 0000000000000000 R09: ffff88810bbb3500 R10: ffff88810bbb3e48 R11: 0000000000000000 R12: ffffc90003067e88 R13: ffffc90003067ea8 R14: ffff888101249800 R15: 00000000fffffffe FS: 00007ff7254fe6c0(0000) GS:ffff888237c00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000555557262da8 CR3: 000000010a6fd000 CR4: 0000000000350ef0 Call Trace: <TASK> iommufd_test_create_access drivers/iommu/iommufd/selftest.c:596 [inline] iommufd_test+0x71c/0xcf0 drivers/iommu/iommufd/selftest.c:813 iommufd_fops_ioctl+0x10f/0x1b0 drivers/iommu/iommufd/main.c:337 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:870 [inline] __se_sys_ioctl fs/ioctl.c:856 [inline] __x64_sys_ioctl+0x84/0xc0 fs/ioctl.c:856 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x38/0x80 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd The solution is to not increment the refcount on the IOMMUFD_DESTROY path at all. Instead use the xa_lock to serialize everything. The refcount check == 1 and xa_erase can be done under a single critical region. This avoids the need for any refcount incrementing. It has the downside that if userspace races destroy with other operations it will get an EBUSY instead of waiting, but this is kind of racing is already dangerous. Fixes: 2ff4bed7fee7 ("iommufd: File descriptor, context, kconfig and makefiles") Link: https://lore.kernel.org/r/2-v1-85aacb2af554+bc-iommufd_syz3_jgg@nvidia.com Reviewed-by: Kevin Tian <kevin.tian@intel.com> Reported-by: syzbot+7574ebfe589049630608@syzkaller.appspotmail.com Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
2023-07-25 16:05:49 -03:00
iommufd_object_ops[obj->type].destroy(obj);
kfree(obj);
iommufd: Do not UAF during iommufd_put_object() The mixture of kernel and user space lifecycle objects continues to be complicated inside iommufd. The obj->destroy_rwsem is used to bring order to the kernel driver destruction sequence but it cannot be sequenced right with the other refcounts so we end up possibly UAF'ing: BUG: KASAN: slab-use-after-free in __up_read+0x627/0x750 kernel/locking/rwsem.c:1342 Read of size 8 at addr ffff888073cde868 by task syz-executor934/6535 CPU: 1 PID: 6535 Comm: syz-executor934 Not tainted 6.6.0-rc7-syzkaller-00195-g2af9b20dbb39 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/09/2023 Call Trace: <TASK> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xd9/0x1b0 lib/dump_stack.c:106 print_address_description mm/kasan/report.c:364 [inline] print_report+0xc4/0x620 mm/kasan/report.c:475 kasan_report+0xda/0x110 mm/kasan/report.c:588 __up_read+0x627/0x750 kernel/locking/rwsem.c:1342 iommufd_put_object drivers/iommu/iommufd/iommufd_private.h:149 [inline] iommufd_vfio_ioas+0x46c/0x580 drivers/iommu/iommufd/vfio_compat.c:146 iommufd_fops_ioctl+0x347/0x4d0 drivers/iommu/iommufd/main.c:398 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:871 [inline] __se_sys_ioctl fs/ioctl.c:857 [inline] __x64_sys_ioctl+0x18f/0x210 fs/ioctl.c:857 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd There are two races here, the more obvious one: CPU 0 CPU 1 iommufd_put_object() iommufd_destroy() refcount_dec(&obj->users) iommufd_object_remove() kfree() up_read(&obj->destroy_rwsem) // Boom And there is also perhaps some possibility that the rwsem could hit an issue: CPU 0 CPU 1 iommufd_put_object() iommufd_object_destroy_user() refcount_dec(&obj->users); down_write(&obj->destroy_rwsem) up_read(&obj->destroy_rwsem); atomic_long_or(RWSEM_FLAG_WAITERS, &sem->count); tmp = atomic_long_add_return_release() rwsem_try_write_lock() iommufd_object_remove() up_write(&obj->destroy_rwsem) kfree() clear_nonspinnable() // Boom Fix this by reorganizing this again so that two refcounts are used to keep track of things with a rule that users == 0 && shortterm_users == 0 means no other threads have that memory. Put a wait_queue in the iommufd_ctx object that is triggered when any sub object reaches a 0 shortterm_users. This allows the same wait for userspace ioctls to finish behavior that the rwsem was providing. This is weaker still than the prior versions: - There is no bias on shortterm_users so if some thread is waiting to destroy other threads can continue to get new read sides - If destruction fails, eg because of an active in-kernel user, then shortterm_users will have cycled to zero momentarily blocking new users - If userspace races destroy with other userspace operations they continue to get an EBUSY since we still can't intermix looking up an ID and sleeping for its unref In all cases these are things that userspace brings on itself, correct programs will not hit them. Fixes: 99f98a7c0d69 ("iommufd: IOMMUFD_DESTROY should not increase the refcount") Link: https://lore.kernel.org/all/2-v2-ca9e00171c5b+123-iommufd_syz4_jgg@nvidia.com/ Reported-by: syzbot+d31adfb277377ef8fcba@syzkaller.appspotmail.com Closes: https://lore.kernel.org/r/00000000000055ef9a0609336580@google.com Reviewed-by: Kevin Tian <kevin.tian@intel.com> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
2023-11-12 15:44:08 -04:00
return 0;
err_xa:
if (zerod_wait_cnt) {
iommufd: Do not UAF during iommufd_put_object() The mixture of kernel and user space lifecycle objects continues to be complicated inside iommufd. The obj->destroy_rwsem is used to bring order to the kernel driver destruction sequence but it cannot be sequenced right with the other refcounts so we end up possibly UAF'ing: BUG: KASAN: slab-use-after-free in __up_read+0x627/0x750 kernel/locking/rwsem.c:1342 Read of size 8 at addr ffff888073cde868 by task syz-executor934/6535 CPU: 1 PID: 6535 Comm: syz-executor934 Not tainted 6.6.0-rc7-syzkaller-00195-g2af9b20dbb39 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/09/2023 Call Trace: <TASK> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xd9/0x1b0 lib/dump_stack.c:106 print_address_description mm/kasan/report.c:364 [inline] print_report+0xc4/0x620 mm/kasan/report.c:475 kasan_report+0xda/0x110 mm/kasan/report.c:588 __up_read+0x627/0x750 kernel/locking/rwsem.c:1342 iommufd_put_object drivers/iommu/iommufd/iommufd_private.h:149 [inline] iommufd_vfio_ioas+0x46c/0x580 drivers/iommu/iommufd/vfio_compat.c:146 iommufd_fops_ioctl+0x347/0x4d0 drivers/iommu/iommufd/main.c:398 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:871 [inline] __se_sys_ioctl fs/ioctl.c:857 [inline] __x64_sys_ioctl+0x18f/0x210 fs/ioctl.c:857 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd There are two races here, the more obvious one: CPU 0 CPU 1 iommufd_put_object() iommufd_destroy() refcount_dec(&obj->users) iommufd_object_remove() kfree() up_read(&obj->destroy_rwsem) // Boom And there is also perhaps some possibility that the rwsem could hit an issue: CPU 0 CPU 1 iommufd_put_object() iommufd_object_destroy_user() refcount_dec(&obj->users); down_write(&obj->destroy_rwsem) up_read(&obj->destroy_rwsem); atomic_long_or(RWSEM_FLAG_WAITERS, &sem->count); tmp = atomic_long_add_return_release() rwsem_try_write_lock() iommufd_object_remove() up_write(&obj->destroy_rwsem) kfree() clear_nonspinnable() // Boom Fix this by reorganizing this again so that two refcounts are used to keep track of things with a rule that users == 0 && shortterm_users == 0 means no other threads have that memory. Put a wait_queue in the iommufd_ctx object that is triggered when any sub object reaches a 0 shortterm_users. This allows the same wait for userspace ioctls to finish behavior that the rwsem was providing. This is weaker still than the prior versions: - There is no bias on shortterm_users so if some thread is waiting to destroy other threads can continue to get new read sides - If destruction fails, eg because of an active in-kernel user, then shortterm_users will have cycled to zero momentarily blocking new users - If userspace races destroy with other userspace operations they continue to get an EBUSY since we still can't intermix looking up an ID and sleeping for its unref In all cases these are things that userspace brings on itself, correct programs will not hit them. Fixes: 99f98a7c0d69 ("iommufd: IOMMUFD_DESTROY should not increase the refcount") Link: https://lore.kernel.org/all/2-v2-ca9e00171c5b+123-iommufd_syz4_jgg@nvidia.com/ Reported-by: syzbot+d31adfb277377ef8fcba@syzkaller.appspotmail.com Closes: https://lore.kernel.org/r/00000000000055ef9a0609336580@google.com Reviewed-by: Kevin Tian <kevin.tian@intel.com> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
2023-11-12 15:44:08 -04:00
/* Restore the xarray owned reference */
refcount_set(&obj->wait_cnt, 1);
iommufd: Do not UAF during iommufd_put_object() The mixture of kernel and user space lifecycle objects continues to be complicated inside iommufd. The obj->destroy_rwsem is used to bring order to the kernel driver destruction sequence but it cannot be sequenced right with the other refcounts so we end up possibly UAF'ing: BUG: KASAN: slab-use-after-free in __up_read+0x627/0x750 kernel/locking/rwsem.c:1342 Read of size 8 at addr ffff888073cde868 by task syz-executor934/6535 CPU: 1 PID: 6535 Comm: syz-executor934 Not tainted 6.6.0-rc7-syzkaller-00195-g2af9b20dbb39 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/09/2023 Call Trace: <TASK> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xd9/0x1b0 lib/dump_stack.c:106 print_address_description mm/kasan/report.c:364 [inline] print_report+0xc4/0x620 mm/kasan/report.c:475 kasan_report+0xda/0x110 mm/kasan/report.c:588 __up_read+0x627/0x750 kernel/locking/rwsem.c:1342 iommufd_put_object drivers/iommu/iommufd/iommufd_private.h:149 [inline] iommufd_vfio_ioas+0x46c/0x580 drivers/iommu/iommufd/vfio_compat.c:146 iommufd_fops_ioctl+0x347/0x4d0 drivers/iommu/iommufd/main.c:398 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:871 [inline] __se_sys_ioctl fs/ioctl.c:857 [inline] __x64_sys_ioctl+0x18f/0x210 fs/ioctl.c:857 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd There are two races here, the more obvious one: CPU 0 CPU 1 iommufd_put_object() iommufd_destroy() refcount_dec(&obj->users) iommufd_object_remove() kfree() up_read(&obj->destroy_rwsem) // Boom And there is also perhaps some possibility that the rwsem could hit an issue: CPU 0 CPU 1 iommufd_put_object() iommufd_object_destroy_user() refcount_dec(&obj->users); down_write(&obj->destroy_rwsem) up_read(&obj->destroy_rwsem); atomic_long_or(RWSEM_FLAG_WAITERS, &sem->count); tmp = atomic_long_add_return_release() rwsem_try_write_lock() iommufd_object_remove() up_write(&obj->destroy_rwsem) kfree() clear_nonspinnable() // Boom Fix this by reorganizing this again so that two refcounts are used to keep track of things with a rule that users == 0 && shortterm_users == 0 means no other threads have that memory. Put a wait_queue in the iommufd_ctx object that is triggered when any sub object reaches a 0 shortterm_users. This allows the same wait for userspace ioctls to finish behavior that the rwsem was providing. This is weaker still than the prior versions: - There is no bias on shortterm_users so if some thread is waiting to destroy other threads can continue to get new read sides - If destruction fails, eg because of an active in-kernel user, then shortterm_users will have cycled to zero momentarily blocking new users - If userspace races destroy with other userspace operations they continue to get an EBUSY since we still can't intermix looking up an ID and sleeping for its unref In all cases these are things that userspace brings on itself, correct programs will not hit them. Fixes: 99f98a7c0d69 ("iommufd: IOMMUFD_DESTROY should not increase the refcount") Link: https://lore.kernel.org/all/2-v2-ca9e00171c5b+123-iommufd_syz4_jgg@nvidia.com/ Reported-by: syzbot+d31adfb277377ef8fcba@syzkaller.appspotmail.com Closes: https://lore.kernel.org/r/00000000000055ef9a0609336580@google.com Reviewed-by: Kevin Tian <kevin.tian@intel.com> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
2023-11-12 15:44:08 -04:00
}
xa_unlock(&ictx->objects);
/* The returned object reference count is zero */
return ret;
}
static int iommufd_destroy(struct iommufd_ucmd *ucmd)
{
struct iommu_destroy *cmd = ucmd->cmd;
iommufd: Do not UAF during iommufd_put_object() The mixture of kernel and user space lifecycle objects continues to be complicated inside iommufd. The obj->destroy_rwsem is used to bring order to the kernel driver destruction sequence but it cannot be sequenced right with the other refcounts so we end up possibly UAF'ing: BUG: KASAN: slab-use-after-free in __up_read+0x627/0x750 kernel/locking/rwsem.c:1342 Read of size 8 at addr ffff888073cde868 by task syz-executor934/6535 CPU: 1 PID: 6535 Comm: syz-executor934 Not tainted 6.6.0-rc7-syzkaller-00195-g2af9b20dbb39 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/09/2023 Call Trace: <TASK> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xd9/0x1b0 lib/dump_stack.c:106 print_address_description mm/kasan/report.c:364 [inline] print_report+0xc4/0x620 mm/kasan/report.c:475 kasan_report+0xda/0x110 mm/kasan/report.c:588 __up_read+0x627/0x750 kernel/locking/rwsem.c:1342 iommufd_put_object drivers/iommu/iommufd/iommufd_private.h:149 [inline] iommufd_vfio_ioas+0x46c/0x580 drivers/iommu/iommufd/vfio_compat.c:146 iommufd_fops_ioctl+0x347/0x4d0 drivers/iommu/iommufd/main.c:398 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:871 [inline] __se_sys_ioctl fs/ioctl.c:857 [inline] __x64_sys_ioctl+0x18f/0x210 fs/ioctl.c:857 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd There are two races here, the more obvious one: CPU 0 CPU 1 iommufd_put_object() iommufd_destroy() refcount_dec(&obj->users) iommufd_object_remove() kfree() up_read(&obj->destroy_rwsem) // Boom And there is also perhaps some possibility that the rwsem could hit an issue: CPU 0 CPU 1 iommufd_put_object() iommufd_object_destroy_user() refcount_dec(&obj->users); down_write(&obj->destroy_rwsem) up_read(&obj->destroy_rwsem); atomic_long_or(RWSEM_FLAG_WAITERS, &sem->count); tmp = atomic_long_add_return_release() rwsem_try_write_lock() iommufd_object_remove() up_write(&obj->destroy_rwsem) kfree() clear_nonspinnable() // Boom Fix this by reorganizing this again so that two refcounts are used to keep track of things with a rule that users == 0 && shortterm_users == 0 means no other threads have that memory. Put a wait_queue in the iommufd_ctx object that is triggered when any sub object reaches a 0 shortterm_users. This allows the same wait for userspace ioctls to finish behavior that the rwsem was providing. This is weaker still than the prior versions: - There is no bias on shortterm_users so if some thread is waiting to destroy other threads can continue to get new read sides - If destruction fails, eg because of an active in-kernel user, then shortterm_users will have cycled to zero momentarily blocking new users - If userspace races destroy with other userspace operations they continue to get an EBUSY since we still can't intermix looking up an ID and sleeping for its unref In all cases these are things that userspace brings on itself, correct programs will not hit them. Fixes: 99f98a7c0d69 ("iommufd: IOMMUFD_DESTROY should not increase the refcount") Link: https://lore.kernel.org/all/2-v2-ca9e00171c5b+123-iommufd_syz4_jgg@nvidia.com/ Reported-by: syzbot+d31adfb277377ef8fcba@syzkaller.appspotmail.com Closes: https://lore.kernel.org/r/00000000000055ef9a0609336580@google.com Reviewed-by: Kevin Tian <kevin.tian@intel.com> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
2023-11-12 15:44:08 -04:00
return iommufd_object_remove(ucmd->ictx, NULL, cmd->id, 0);
}
static int iommufd_fops_open(struct inode *inode, struct file *filp)
{
struct iommufd_ctx *ictx;
ictx = kzalloc(sizeof(*ictx), GFP_KERNEL_ACCOUNT);
if (!ictx)
return -ENOMEM;
/*
* For compatibility with VFIO when /dev/vfio/vfio is opened we default
* to the same rlimit accounting as vfio uses.
*/
if (IS_ENABLED(CONFIG_IOMMUFD_VFIO_CONTAINER) &&
filp->private_data == &vfio_misc_dev) {
ictx->account_mode = IOPT_PAGES_ACCOUNT_MM;
pr_info_once("IOMMUFD is providing /dev/vfio/vfio, not VFIO.\n");
}
init_rwsem(&ictx->ioas_creation_lock);
xa_init_flags(&ictx->objects, XA_FLAGS_ALLOC1 | XA_FLAGS_ACCOUNT);
xa_init(&ictx->groups);
ictx->file = filp;
mt_init_flags(&ictx->mt_mmap, MT_FLAGS_ALLOC_RANGE);
iommufd: Do not UAF during iommufd_put_object() The mixture of kernel and user space lifecycle objects continues to be complicated inside iommufd. The obj->destroy_rwsem is used to bring order to the kernel driver destruction sequence but it cannot be sequenced right with the other refcounts so we end up possibly UAF'ing: BUG: KASAN: slab-use-after-free in __up_read+0x627/0x750 kernel/locking/rwsem.c:1342 Read of size 8 at addr ffff888073cde868 by task syz-executor934/6535 CPU: 1 PID: 6535 Comm: syz-executor934 Not tainted 6.6.0-rc7-syzkaller-00195-g2af9b20dbb39 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/09/2023 Call Trace: <TASK> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xd9/0x1b0 lib/dump_stack.c:106 print_address_description mm/kasan/report.c:364 [inline] print_report+0xc4/0x620 mm/kasan/report.c:475 kasan_report+0xda/0x110 mm/kasan/report.c:588 __up_read+0x627/0x750 kernel/locking/rwsem.c:1342 iommufd_put_object drivers/iommu/iommufd/iommufd_private.h:149 [inline] iommufd_vfio_ioas+0x46c/0x580 drivers/iommu/iommufd/vfio_compat.c:146 iommufd_fops_ioctl+0x347/0x4d0 drivers/iommu/iommufd/main.c:398 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:871 [inline] __se_sys_ioctl fs/ioctl.c:857 [inline] __x64_sys_ioctl+0x18f/0x210 fs/ioctl.c:857 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd There are two races here, the more obvious one: CPU 0 CPU 1 iommufd_put_object() iommufd_destroy() refcount_dec(&obj->users) iommufd_object_remove() kfree() up_read(&obj->destroy_rwsem) // Boom And there is also perhaps some possibility that the rwsem could hit an issue: CPU 0 CPU 1 iommufd_put_object() iommufd_object_destroy_user() refcount_dec(&obj->users); down_write(&obj->destroy_rwsem) up_read(&obj->destroy_rwsem); atomic_long_or(RWSEM_FLAG_WAITERS, &sem->count); tmp = atomic_long_add_return_release() rwsem_try_write_lock() iommufd_object_remove() up_write(&obj->destroy_rwsem) kfree() clear_nonspinnable() // Boom Fix this by reorganizing this again so that two refcounts are used to keep track of things with a rule that users == 0 && shortterm_users == 0 means no other threads have that memory. Put a wait_queue in the iommufd_ctx object that is triggered when any sub object reaches a 0 shortterm_users. This allows the same wait for userspace ioctls to finish behavior that the rwsem was providing. This is weaker still than the prior versions: - There is no bias on shortterm_users so if some thread is waiting to destroy other threads can continue to get new read sides - If destruction fails, eg because of an active in-kernel user, then shortterm_users will have cycled to zero momentarily blocking new users - If userspace races destroy with other userspace operations they continue to get an EBUSY since we still can't intermix looking up an ID and sleeping for its unref In all cases these are things that userspace brings on itself, correct programs will not hit them. Fixes: 99f98a7c0d69 ("iommufd: IOMMUFD_DESTROY should not increase the refcount") Link: https://lore.kernel.org/all/2-v2-ca9e00171c5b+123-iommufd_syz4_jgg@nvidia.com/ Reported-by: syzbot+d31adfb277377ef8fcba@syzkaller.appspotmail.com Closes: https://lore.kernel.org/r/00000000000055ef9a0609336580@google.com Reviewed-by: Kevin Tian <kevin.tian@intel.com> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
2023-11-12 15:44:08 -04:00
init_waitqueue_head(&ictx->destroy_wait);
mutex_init(&ictx->sw_msi_lock);
INIT_LIST_HEAD(&ictx->sw_msi_list);
filp->private_data = ictx;
return 0;
}
static int iommufd_fops_release(struct inode *inode, struct file *filp)
{
struct iommufd_ctx *ictx = filp->private_data;
struct iommufd_sw_msi_map *next;
struct iommufd_sw_msi_map *cur;
struct iommufd_object *obj;
/*
* The objects in the xarray form a graph of "users" counts, and we have
* to destroy them in a depth first manner. Leaf objects will reduce the
* users count of interior objects when they are destroyed.
*
* Repeatedly destroying all the "1 users" leaf objects will progress
* until the entire list is destroyed. If this can't progress then there
* is some bug related to object refcounting.
*/
while (!xa_empty(&ictx->objects)) {
unsigned int destroyed = 0;
unsigned long index;
bool empty = true;
/*
* We can't use xa_empty() to end the loop as the tombstones
* are stored as XA_ZERO_ENTRY in the xarray. However
* xa_for_each() automatically converts them to NULL and skips
* them causing xa_empty() to be kept false. Thus once
* xa_for_each() finds no further !NULL entries the loop is
* done.
*/
xa_for_each(&ictx->objects, index, obj) {
empty = false;
if (!refcount_dec_if_one(&obj->users))
continue;
destroyed++;
xa_erase(&ictx->objects, index);
iommufd_object_ops[obj->type].destroy(obj);
kfree(obj);
}
if (empty)
break;
/* Bug related to users refcount */
if (WARN_ON(!destroyed))
break;
}
/*
* There may be some tombstones left over from
* iommufd_object_tombstone_user()
*/
xa_destroy(&ictx->objects);
WARN_ON(!xa_empty(&ictx->groups));
mutex_destroy(&ictx->sw_msi_lock);
list_for_each_entry_safe(cur, next, &ictx->sw_msi_list, sw_msi_item)
kfree(cur);
kfree(ictx);
return 0;
}
static int iommufd_option(struct iommufd_ucmd *ucmd)
{
struct iommu_option *cmd = ucmd->cmd;
int rc;
if (cmd->__reserved)
return -EOPNOTSUPP;
switch (cmd->option_id) {
case IOMMU_OPTION_RLIMIT_MODE:
rc = iommufd_option_rlimit_mode(cmd, ucmd->ictx);
break;
case IOMMU_OPTION_HUGE_PAGES:
rc = iommufd_ioas_option(ucmd);
break;
default:
return -EOPNOTSUPP;
}
if (rc)
return rc;
if (copy_to_user(&((struct iommu_option __user *)ucmd->ubuffer)->val64,
&cmd->val64, sizeof(cmd->val64)))
return -EFAULT;
return 0;
}
union ucmd_buffer {
struct iommu_destroy destroy;
struct iommu_fault_alloc fault;
struct iommu_hw_info info;
struct iommu_hw_queue_alloc hw_queue;
struct iommu_hwpt_alloc hwpt;
struct iommu_hwpt_get_dirty_bitmap get_dirty_bitmap;
struct iommu_hwpt_invalidate cache;
struct iommu_hwpt_set_dirty_tracking set_dirty_tracking;
struct iommu_ioas_alloc alloc;
struct iommu_ioas_allow_iovas allow_iovas;
struct iommu_ioas_copy ioas_copy;
struct iommu_ioas_iova_ranges iova_ranges;
struct iommu_ioas_map map;
struct iommu_ioas_unmap unmap;
struct iommu_option option;
struct iommu_vdevice_alloc vdev;
struct iommu_veventq_alloc veventq;
struct iommu_vfio_ioas vfio_ioas;
struct iommu_viommu_alloc viommu;
#ifdef CONFIG_IOMMUFD_TEST
struct iommu_test_cmd test;
#endif
};
struct iommufd_ioctl_op {
unsigned int size;
unsigned int min_size;
unsigned int ioctl_num;
int (*execute)(struct iommufd_ucmd *ucmd);
};
#define IOCTL_OP(_ioctl, _fn, _struct, _last) \
[_IOC_NR(_ioctl) - IOMMUFD_CMD_BASE] = { \
.size = sizeof(_struct) + \
BUILD_BUG_ON_ZERO(sizeof(union ucmd_buffer) < \
sizeof(_struct)), \
.min_size = offsetofend(_struct, _last), \
.ioctl_num = _ioctl, \
.execute = _fn, \
}
static const struct iommufd_ioctl_op iommufd_ioctl_ops[] = {
IOCTL_OP(IOMMU_DESTROY, iommufd_destroy, struct iommu_destroy, id),
IOCTL_OP(IOMMU_FAULT_QUEUE_ALLOC, iommufd_fault_alloc,
struct iommu_fault_alloc, out_fault_fd),
IOCTL_OP(IOMMU_GET_HW_INFO, iommufd_get_hw_info, struct iommu_hw_info,
__reserved),
IOCTL_OP(IOMMU_HW_QUEUE_ALLOC, iommufd_hw_queue_alloc_ioctl,
struct iommu_hw_queue_alloc, length),
IOCTL_OP(IOMMU_HWPT_ALLOC, iommufd_hwpt_alloc, struct iommu_hwpt_alloc,
__reserved),
IOCTL_OP(IOMMU_HWPT_GET_DIRTY_BITMAP, iommufd_hwpt_get_dirty_bitmap,
struct iommu_hwpt_get_dirty_bitmap, data),
IOCTL_OP(IOMMU_HWPT_INVALIDATE, iommufd_hwpt_invalidate,
struct iommu_hwpt_invalidate, __reserved),
IOCTL_OP(IOMMU_HWPT_SET_DIRTY_TRACKING, iommufd_hwpt_set_dirty_tracking,
struct iommu_hwpt_set_dirty_tracking, __reserved),
IOCTL_OP(IOMMU_IOAS_ALLOC, iommufd_ioas_alloc_ioctl,
struct iommu_ioas_alloc, out_ioas_id),
IOCTL_OP(IOMMU_IOAS_ALLOW_IOVAS, iommufd_ioas_allow_iovas,
struct iommu_ioas_allow_iovas, allowed_iovas),
IOCTL_OP(IOMMU_IOAS_CHANGE_PROCESS, iommufd_ioas_change_process,
struct iommu_ioas_change_process, __reserved),
IOCTL_OP(IOMMU_IOAS_COPY, iommufd_ioas_copy, struct iommu_ioas_copy,
src_iova),
IOCTL_OP(IOMMU_IOAS_IOVA_RANGES, iommufd_ioas_iova_ranges,
struct iommu_ioas_iova_ranges, out_iova_alignment),
IOCTL_OP(IOMMU_IOAS_MAP, iommufd_ioas_map, struct iommu_ioas_map, iova),
IOCTL_OP(IOMMU_IOAS_MAP_FILE, iommufd_ioas_map_file,
struct iommu_ioas_map_file, iova),
IOCTL_OP(IOMMU_IOAS_UNMAP, iommufd_ioas_unmap, struct iommu_ioas_unmap,
length),
IOCTL_OP(IOMMU_OPTION, iommufd_option, struct iommu_option, val64),
IOCTL_OP(IOMMU_VDEVICE_ALLOC, iommufd_vdevice_alloc_ioctl,
struct iommu_vdevice_alloc, virt_id),
IOCTL_OP(IOMMU_VEVENTQ_ALLOC, iommufd_veventq_alloc,
struct iommu_veventq_alloc, out_veventq_fd),
iommufd: vfio container FD ioctl compatibility iommufd can directly implement the /dev/vfio/vfio container IOCTLs by mapping them into io_pagetable operations. A userspace application can test against iommufd and confirm compatibility then simply make a small change to open /dev/iommu instead of /dev/vfio/vfio. For testing purposes /dev/vfio/vfio can be symlinked to /dev/iommu and then all applications will use the compatibility path with no code changes. A later series allows /dev/vfio/vfio to be directly provided by iommufd, which allows the rlimit mode to work the same as well. This series just provides the iommufd side of compatibility. Actually linking this to VFIO_SET_CONTAINER is a followup series, with a link in the cover letter. Internally the compatibility API uses a normal IOAS object that, like vfio, is automatically allocated when the first device is attached. Userspace can also query or set this IOAS object directly using the IOMMU_VFIO_IOAS ioctl. This allows mixing and matching new iommufd only features while still using the VFIO style map/unmap ioctls. While this is enough to operate qemu, it has a few differences: - Resource limits rely on memory cgroups to bound what userspace can do instead of the module parameter dma_entry_limit. - VFIO P2P is not implemented. The DMABUF patches for vfio are a start at a solution where iommufd would import a special DMABUF. This is to avoid further propogating the follow_pfn() security problem. - A full audit for pedantic compatibility details (eg errnos, etc) has not yet been done - powerpc SPAPR is left out, as it is not connected to the iommu_domain framework. It seems interest in SPAPR is minimal as it is currently non-working in v6.1-rc1. They will have to convert to the iommu subsystem framework to enjoy iommfd. The following are not going to be implemented and we expect to remove them from VFIO type1: - SW access 'dirty tracking'. As discussed in the cover letter this will be done in VFIO. - VFIO_TYPE1_NESTING_IOMMU https://lore.kernel.org/all/0-v1-0093c9b0e345+19-vfio_no_nesting_jgg@nvidia.com/ - VFIO_DMA_MAP_FLAG_VADDR https://lore.kernel.org/all/Yz777bJZjTyLrHEQ@nvidia.com/ Link: https://lore.kernel.org/r/15-v6-a196d26f289e+11787-iommufd_jgg@nvidia.com Tested-by: Nicolin Chen <nicolinc@nvidia.com> Tested-by: Yi Liu <yi.l.liu@intel.com> Tested-by: Lixiao Yang <lixiao.yang@intel.com> Tested-by: Matthew Rosato <mjrosato@linux.ibm.com> Reviewed-by: Kevin Tian <kevin.tian@intel.com> Reviewed-by: Eric Auger <eric.auger@redhat.com> Signed-off-by: Nicolin Chen <nicolinc@nvidia.com> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
2022-11-29 16:29:38 -04:00
IOCTL_OP(IOMMU_VFIO_IOAS, iommufd_vfio_ioas, struct iommu_vfio_ioas,
__reserved),
IOCTL_OP(IOMMU_VIOMMU_ALLOC, iommufd_viommu_alloc_ioctl,
struct iommu_viommu_alloc, out_viommu_id),
#ifdef CONFIG_IOMMUFD_TEST
IOCTL_OP(IOMMU_TEST_CMD, iommufd_test, struct iommu_test_cmd, last),
#endif
};
static long iommufd_fops_ioctl(struct file *filp, unsigned int cmd,
unsigned long arg)
{
iommufd: vfio container FD ioctl compatibility iommufd can directly implement the /dev/vfio/vfio container IOCTLs by mapping them into io_pagetable operations. A userspace application can test against iommufd and confirm compatibility then simply make a small change to open /dev/iommu instead of /dev/vfio/vfio. For testing purposes /dev/vfio/vfio can be symlinked to /dev/iommu and then all applications will use the compatibility path with no code changes. A later series allows /dev/vfio/vfio to be directly provided by iommufd, which allows the rlimit mode to work the same as well. This series just provides the iommufd side of compatibility. Actually linking this to VFIO_SET_CONTAINER is a followup series, with a link in the cover letter. Internally the compatibility API uses a normal IOAS object that, like vfio, is automatically allocated when the first device is attached. Userspace can also query or set this IOAS object directly using the IOMMU_VFIO_IOAS ioctl. This allows mixing and matching new iommufd only features while still using the VFIO style map/unmap ioctls. While this is enough to operate qemu, it has a few differences: - Resource limits rely on memory cgroups to bound what userspace can do instead of the module parameter dma_entry_limit. - VFIO P2P is not implemented. The DMABUF patches for vfio are a start at a solution where iommufd would import a special DMABUF. This is to avoid further propogating the follow_pfn() security problem. - A full audit for pedantic compatibility details (eg errnos, etc) has not yet been done - powerpc SPAPR is left out, as it is not connected to the iommu_domain framework. It seems interest in SPAPR is minimal as it is currently non-working in v6.1-rc1. They will have to convert to the iommu subsystem framework to enjoy iommfd. The following are not going to be implemented and we expect to remove them from VFIO type1: - SW access 'dirty tracking'. As discussed in the cover letter this will be done in VFIO. - VFIO_TYPE1_NESTING_IOMMU https://lore.kernel.org/all/0-v1-0093c9b0e345+19-vfio_no_nesting_jgg@nvidia.com/ - VFIO_DMA_MAP_FLAG_VADDR https://lore.kernel.org/all/Yz777bJZjTyLrHEQ@nvidia.com/ Link: https://lore.kernel.org/r/15-v6-a196d26f289e+11787-iommufd_jgg@nvidia.com Tested-by: Nicolin Chen <nicolinc@nvidia.com> Tested-by: Yi Liu <yi.l.liu@intel.com> Tested-by: Lixiao Yang <lixiao.yang@intel.com> Tested-by: Matthew Rosato <mjrosato@linux.ibm.com> Reviewed-by: Kevin Tian <kevin.tian@intel.com> Reviewed-by: Eric Auger <eric.auger@redhat.com> Signed-off-by: Nicolin Chen <nicolinc@nvidia.com> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
2022-11-29 16:29:38 -04:00
struct iommufd_ctx *ictx = filp->private_data;
const struct iommufd_ioctl_op *op;
struct iommufd_ucmd ucmd = {};
union ucmd_buffer buf;
unsigned int nr;
int ret;
iommufd: vfio container FD ioctl compatibility iommufd can directly implement the /dev/vfio/vfio container IOCTLs by mapping them into io_pagetable operations. A userspace application can test against iommufd and confirm compatibility then simply make a small change to open /dev/iommu instead of /dev/vfio/vfio. For testing purposes /dev/vfio/vfio can be symlinked to /dev/iommu and then all applications will use the compatibility path with no code changes. A later series allows /dev/vfio/vfio to be directly provided by iommufd, which allows the rlimit mode to work the same as well. This series just provides the iommufd side of compatibility. Actually linking this to VFIO_SET_CONTAINER is a followup series, with a link in the cover letter. Internally the compatibility API uses a normal IOAS object that, like vfio, is automatically allocated when the first device is attached. Userspace can also query or set this IOAS object directly using the IOMMU_VFIO_IOAS ioctl. This allows mixing and matching new iommufd only features while still using the VFIO style map/unmap ioctls. While this is enough to operate qemu, it has a few differences: - Resource limits rely on memory cgroups to bound what userspace can do instead of the module parameter dma_entry_limit. - VFIO P2P is not implemented. The DMABUF patches for vfio are a start at a solution where iommufd would import a special DMABUF. This is to avoid further propogating the follow_pfn() security problem. - A full audit for pedantic compatibility details (eg errnos, etc) has not yet been done - powerpc SPAPR is left out, as it is not connected to the iommu_domain framework. It seems interest in SPAPR is minimal as it is currently non-working in v6.1-rc1. They will have to convert to the iommu subsystem framework to enjoy iommfd. The following are not going to be implemented and we expect to remove them from VFIO type1: - SW access 'dirty tracking'. As discussed in the cover letter this will be done in VFIO. - VFIO_TYPE1_NESTING_IOMMU https://lore.kernel.org/all/0-v1-0093c9b0e345+19-vfio_no_nesting_jgg@nvidia.com/ - VFIO_DMA_MAP_FLAG_VADDR https://lore.kernel.org/all/Yz777bJZjTyLrHEQ@nvidia.com/ Link: https://lore.kernel.org/r/15-v6-a196d26f289e+11787-iommufd_jgg@nvidia.com Tested-by: Nicolin Chen <nicolinc@nvidia.com> Tested-by: Yi Liu <yi.l.liu@intel.com> Tested-by: Lixiao Yang <lixiao.yang@intel.com> Tested-by: Matthew Rosato <mjrosato@linux.ibm.com> Reviewed-by: Kevin Tian <kevin.tian@intel.com> Reviewed-by: Eric Auger <eric.auger@redhat.com> Signed-off-by: Nicolin Chen <nicolinc@nvidia.com> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
2022-11-29 16:29:38 -04:00
nr = _IOC_NR(cmd);
if (nr < IOMMUFD_CMD_BASE ||
(nr - IOMMUFD_CMD_BASE) >= ARRAY_SIZE(iommufd_ioctl_ops))
return iommufd_vfio_ioctl(ictx, cmd, arg);
ucmd.ictx = ictx;
ucmd.ubuffer = (void __user *)arg;
ret = get_user(ucmd.user_size, (u32 __user *)ucmd.ubuffer);
if (ret)
return ret;
op = &iommufd_ioctl_ops[nr - IOMMUFD_CMD_BASE];
if (op->ioctl_num != cmd)
return -ENOIOCTLCMD;
if (ucmd.user_size < op->min_size)
return -EINVAL;
ucmd.cmd = &buf;
ret = copy_struct_from_user(ucmd.cmd, op->size, ucmd.ubuffer,
ucmd.user_size);
if (ret)
return ret;
ret = op->execute(&ucmd);
if (ucmd.new_obj) {
if (ret)
iommufd_object_abort_and_destroy(ictx, ucmd.new_obj);
else
iommufd_object_finalize(ictx, ucmd.new_obj);
}
return ret;
}
static void iommufd_fops_vma_open(struct vm_area_struct *vma)
{
struct iommufd_mmap *immap = vma->vm_private_data;
refcount_inc(&immap->owner->users);
}
static void iommufd_fops_vma_close(struct vm_area_struct *vma)
{
struct iommufd_mmap *immap = vma->vm_private_data;
refcount_dec(&immap->owner->users);
}
static const struct vm_operations_struct iommufd_vma_ops = {
.open = iommufd_fops_vma_open,
.close = iommufd_fops_vma_close,
};
/* The vm_pgoff must be pre-allocated from mt_mmap, and given to user space */
static int iommufd_fops_mmap(struct file *filp, struct vm_area_struct *vma)
{
struct iommufd_ctx *ictx = filp->private_data;
size_t length = vma->vm_end - vma->vm_start;
struct iommufd_mmap *immap;
int rc;
if (!PAGE_ALIGNED(length))
return -EINVAL;
if (!(vma->vm_flags & VM_SHARED))
return -EINVAL;
if (vma->vm_flags & VM_EXEC)
return -EPERM;
/* vma->vm_pgoff carries a page-shifted start position to an immap */
immap = mtree_load(&ictx->mt_mmap, vma->vm_pgoff << PAGE_SHIFT);
if (!immap)
return -ENXIO;
/*
* mtree_load() returns the immap for any contained mmio_addr, so only
* allow the exact immap thing to be mapped
*/
if (vma->vm_pgoff != immap->vm_pgoff || length != immap->length)
return -ENXIO;
vma->vm_pgoff = 0;
vma->vm_private_data = immap;
vma->vm_ops = &iommufd_vma_ops;
vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
rc = io_remap_pfn_range(vma, vma->vm_start,
immap->mmio_addr >> PAGE_SHIFT, length,
vma->vm_page_prot);
if (rc)
return rc;
/* vm_ops.open won't be called for mmap itself. */
refcount_inc(&immap->owner->users);
return rc;
}
static const struct file_operations iommufd_fops = {
.owner = THIS_MODULE,
.open = iommufd_fops_open,
.release = iommufd_fops_release,
.unlocked_ioctl = iommufd_fops_ioctl,
.mmap = iommufd_fops_mmap,
};
/**
* iommufd_ctx_get - Get a context reference
* @ictx: Context to get
*
* The caller must already hold a valid reference to ictx.
*/
void iommufd_ctx_get(struct iommufd_ctx *ictx)
{
get_file(ictx->file);
}
EXPORT_SYMBOL_NS_GPL(iommufd_ctx_get, "IOMMUFD");
/**
* iommufd_ctx_from_file - Acquires a reference to the iommufd context
* @file: File to obtain the reference from
*
* Returns a pointer to the iommufd_ctx, otherwise ERR_PTR. The struct file
* remains owned by the caller and the caller must still do fput. On success
* the caller is responsible to call iommufd_ctx_put().
*/
struct iommufd_ctx *iommufd_ctx_from_file(struct file *file)
{
struct iommufd_ctx *ictx;
if (file->f_op != &iommufd_fops)
return ERR_PTR(-EBADFD);
ictx = file->private_data;
iommufd_ctx_get(ictx);
return ictx;
}
EXPORT_SYMBOL_NS_GPL(iommufd_ctx_from_file, "IOMMUFD");
/**
* iommufd_ctx_from_fd - Acquires a reference to the iommufd context
* @fd: File descriptor to obtain the reference from
*
* Returns a pointer to the iommufd_ctx, otherwise ERR_PTR. On success
* the caller is responsible to call iommufd_ctx_put().
*/
struct iommufd_ctx *iommufd_ctx_from_fd(int fd)
{
struct file *file;
file = fget(fd);
if (!file)
return ERR_PTR(-EBADF);
if (file->f_op != &iommufd_fops) {
fput(file);
return ERR_PTR(-EBADFD);
}
/* fget is the same as iommufd_ctx_get() */
return file->private_data;
}
EXPORT_SYMBOL_NS_GPL(iommufd_ctx_from_fd, "IOMMUFD");
/**
* iommufd_ctx_put - Put back a reference
* @ictx: Context to put back
*/
void iommufd_ctx_put(struct iommufd_ctx *ictx)
{
fput(ictx->file);
}
EXPORT_SYMBOL_NS_GPL(iommufd_ctx_put, "IOMMUFD");
static const struct iommufd_object_ops iommufd_object_ops[] = {
[IOMMUFD_OBJ_ACCESS] = {
.destroy = iommufd_access_destroy_object,
},
[IOMMUFD_OBJ_DEVICE] = {
iommufd: Destroy vdevice on idevice destroy Destroy iommufd_vdevice (vdev) on iommufd_idevice (idev) destruction so that vdev can't outlive idev. idev represents the physical device bound to iommufd, while the vdev represents the virtual instance of the physical device in the VM. The lifecycle of the vdev should not be longer than idev. This doesn't cause real problem on existing use cases cause vdev doesn't impact the physical device, only provides virtualization information. But to extend vdev for Confidential Computing (CC), there are needs to do secure configuration for the vdev, e.g. TSM Bind/Unbind. These configurations should be rolled back on idev destroy, or the external driver (VFIO) functionality may be impact. The idev is created by external driver so its destruction can't fail. The idev implements pre_destroy() op to actively remove its associated vdev before destroying itself. There are 3 cases on idev pre_destroy(): 1. vdev is already destroyed by userspace. No extra handling needed. 2. vdev is still alive. Use iommufd_object_tombstone_user() to destroy vdev and tombstone the vdev ID. 3. vdev is being destroyed by userspace. The vdev ID is already freed, but vdev destroy handler is not completed. This requires multi-threads syncing - vdev holds idev's short term users reference until vdev destruction completes, idev leverages existing wait_shortterm mechanism for syncing. idev should also block any new reference to it after pre_destroy(), or the following wait shortterm would timeout. Introduce a 'destroying' flag, set it to true on idev pre_destroy(). Any attempt to reference idev should honor this flag under the protection of idev->igroup->lock. Link: https://patch.msgid.link/r/20250716070349.1807226-5-yilun.xu@linux.intel.com Originally-by: Nicolin Chen <nicolinc@nvidia.com> Suggested-by: Jason Gunthorpe <jgg@nvidia.com> Reviewed-by: Kevin Tian <kevin.tian@intel.com> Reviewed-by: Nicolin Chen <nicolinc@nvidia.com> Reviewed-by: Jason Gunthorpe <jgg@nvidia.com> Co-developed-by: "Aneesh Kumar K.V (Arm)" <aneesh.kumar@kernel.org> Signed-off-by: "Aneesh Kumar K.V (Arm)" <aneesh.kumar@kernel.org> Tested-by: Nicolin Chen <nicolinc@nvidia.com> Signed-off-by: Xu Yilun <yilun.xu@linux.intel.com> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
2025-07-16 15:03:45 +08:00
.pre_destroy = iommufd_device_pre_destroy,
.destroy = iommufd_device_destroy,
},
[IOMMUFD_OBJ_FAULT] = {
.destroy = iommufd_fault_destroy,
},
[IOMMUFD_OBJ_HW_QUEUE] = {
.destroy = iommufd_hw_queue_destroy,
},
[IOMMUFD_OBJ_HWPT_PAGING] = {
.destroy = iommufd_hwpt_paging_destroy,
.abort = iommufd_hwpt_paging_abort,
iommufd: Add a HW pagetable object The hw_pagetable object exposes the internal struct iommu_domain's to userspace. An iommu_domain is required when any DMA device attaches to an IOAS to control the io page table through the iommu driver. For compatibility with VFIO the hw_pagetable is automatically created when a DMA device is attached to the IOAS. If a compatible iommu_domain already exists then the hw_pagetable associated with it is used for the attachment. In the initial series there is no iommufd uAPI for the hw_pagetable object. The next patch provides driver facing APIs for IO page table attachment that allows drivers to accept either an IOAS or a hw_pagetable ID and for the driver to return the hw_pagetable ID that was auto-selected from an IOAS. The expectation is the driver will provide uAPI through its own FD for attaching its device to iommufd. This allows userspace to learn the mapping of devices to iommu_domains and to override the automatic attachment. The future HW specific interface will allow userspace to create hw_pagetable objects using iommu_domains with IOMMU driver specific parameters. This infrastructure will allow linking those domains to IOAS's and devices. Link: https://lore.kernel.org/r/12-v6-a196d26f289e+11787-iommufd_jgg@nvidia.com Reviewed-by: Kevin Tian <kevin.tian@intel.com> Reviewed-by: Eric Auger <eric.auger@redhat.com> Tested-by: Nicolin Chen <nicolinc@nvidia.com> Tested-by: Yi Liu <yi.l.liu@intel.com> Tested-by: Lixiao Yang <lixiao.yang@intel.com> Tested-by: Matthew Rosato <mjrosato@linux.ibm.com> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
2022-11-29 16:29:35 -04:00
},
iommufd: Add a nested HW pagetable object IOMMU_HWPT_ALLOC already supports iommu_domain allocation for usersapce. But it can only allocate a hw_pagetable that associates to a given IOAS, i.e. only a kernel-managed hw_pagetable of IOMMUFD_OBJ_HWPT_PAGING type. IOMMU drivers can now support user-managed hw_pagetables, for two-stage translation use cases that require user data input from the user space. Add a new IOMMUFD_OBJ_HWPT_NESTED type with its abort/destroy(). Pair it with a new iommufd_hwpt_nested structure and its to_hwpt_nested() helper. Update the to_hwpt_paging() helper, so a NESTED-type hw_pagetable can be handled in the callers, for example iommufd_hw_pagetable_enforce_rr(). Screen the inputs including the parent PAGING-type hw_pagetable that has a need of a new nest_parent flag in the iommufd_hwpt_paging structure. Extend the IOMMU_HWPT_ALLOC ioctl to accept an IOMMU driver specific data input which is tagged by the enum iommu_hwpt_data_type. Also, update the @pt_id to accept hwpt_id too besides an ioas_id. Then, use them to allocate a hw_pagetable of IOMMUFD_OBJ_HWPT_NESTED type using the iommufd_hw_pagetable_alloc_nested() allocator. Link: https://lore.kernel.org/r/20231026043938.63898-8-yi.l.liu@intel.com Signed-off-by: Nicolin Chen <nicolinc@nvidia.com> Co-developed-by: Yi Liu <yi.l.liu@intel.com> Signed-off-by: Yi Liu <yi.l.liu@intel.com> Reviewed-by: Kevin Tian <kevin.tian@intel.com> Reviewed-by: Jason Gunthorpe <jgg@nvidia.com> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
2023-10-25 21:39:35 -07:00
[IOMMUFD_OBJ_HWPT_NESTED] = {
.destroy = iommufd_hwpt_nested_destroy,
.abort = iommufd_hwpt_nested_abort,
},
[IOMMUFD_OBJ_IOAS] = {
.destroy = iommufd_ioas_destroy,
},
[IOMMUFD_OBJ_VDEVICE] = {
.destroy = iommufd_vdevice_destroy,
iommufd: Destroy vdevice on idevice destroy Destroy iommufd_vdevice (vdev) on iommufd_idevice (idev) destruction so that vdev can't outlive idev. idev represents the physical device bound to iommufd, while the vdev represents the virtual instance of the physical device in the VM. The lifecycle of the vdev should not be longer than idev. This doesn't cause real problem on existing use cases cause vdev doesn't impact the physical device, only provides virtualization information. But to extend vdev for Confidential Computing (CC), there are needs to do secure configuration for the vdev, e.g. TSM Bind/Unbind. These configurations should be rolled back on idev destroy, or the external driver (VFIO) functionality may be impact. The idev is created by external driver so its destruction can't fail. The idev implements pre_destroy() op to actively remove its associated vdev before destroying itself. There are 3 cases on idev pre_destroy(): 1. vdev is already destroyed by userspace. No extra handling needed. 2. vdev is still alive. Use iommufd_object_tombstone_user() to destroy vdev and tombstone the vdev ID. 3. vdev is being destroyed by userspace. The vdev ID is already freed, but vdev destroy handler is not completed. This requires multi-threads syncing - vdev holds idev's short term users reference until vdev destruction completes, idev leverages existing wait_shortterm mechanism for syncing. idev should also block any new reference to it after pre_destroy(), or the following wait shortterm would timeout. Introduce a 'destroying' flag, set it to true on idev pre_destroy(). Any attempt to reference idev should honor this flag under the protection of idev->igroup->lock. Link: https://patch.msgid.link/r/20250716070349.1807226-5-yilun.xu@linux.intel.com Originally-by: Nicolin Chen <nicolinc@nvidia.com> Suggested-by: Jason Gunthorpe <jgg@nvidia.com> Reviewed-by: Kevin Tian <kevin.tian@intel.com> Reviewed-by: Nicolin Chen <nicolinc@nvidia.com> Reviewed-by: Jason Gunthorpe <jgg@nvidia.com> Co-developed-by: "Aneesh Kumar K.V (Arm)" <aneesh.kumar@kernel.org> Signed-off-by: "Aneesh Kumar K.V (Arm)" <aneesh.kumar@kernel.org> Tested-by: Nicolin Chen <nicolinc@nvidia.com> Signed-off-by: Xu Yilun <yilun.xu@linux.intel.com> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
2025-07-16 15:03:45 +08:00
.abort = iommufd_vdevice_abort,
},
[IOMMUFD_OBJ_VEVENTQ] = {
.destroy = iommufd_veventq_destroy,
.abort = iommufd_veventq_abort,
},
[IOMMUFD_OBJ_VIOMMU] = {
.destroy = iommufd_viommu_destroy,
},
#ifdef CONFIG_IOMMUFD_TEST
[IOMMUFD_OBJ_SELFTEST] = {
.destroy = iommufd_selftest_destroy,
},
#endif
};
static struct miscdevice iommu_misc_dev = {
.minor = MISC_DYNAMIC_MINOR,
.name = "iommu",
.fops = &iommufd_fops,
.nodename = "iommu",
.mode = 0660,
};
static struct miscdevice vfio_misc_dev = {
.minor = VFIO_MINOR,
.name = "vfio",
.fops = &iommufd_fops,
.nodename = "vfio/vfio",
.mode = 0666,
};
static int __init iommufd_init(void)
{
int ret;
ret = misc_register(&iommu_misc_dev);
if (ret)
return ret;
if (IS_ENABLED(CONFIG_IOMMUFD_VFIO_CONTAINER)) {
ret = misc_register(&vfio_misc_dev);
if (ret)
goto err_misc;
}
ret = iommufd_test_init();
if (ret)
goto err_vfio_misc;
return 0;
err_vfio_misc:
if (IS_ENABLED(CONFIG_IOMMUFD_VFIO_CONTAINER))
misc_deregister(&vfio_misc_dev);
err_misc:
misc_deregister(&iommu_misc_dev);
return ret;
}
static void __exit iommufd_exit(void)
{
iommufd_test_exit();
if (IS_ENABLED(CONFIG_IOMMUFD_VFIO_CONTAINER))
misc_deregister(&vfio_misc_dev);
misc_deregister(&iommu_misc_dev);
}
module_init(iommufd_init);
module_exit(iommufd_exit);
#if IS_ENABLED(CONFIG_IOMMUFD_VFIO_CONTAINER)
MODULE_ALIAS_MISCDEV(VFIO_MINOR);
MODULE_ALIAS("devname:vfio/vfio");
#endif
MODULE_IMPORT_NS("IOMMUFD_INTERNAL");
MODULE_IMPORT_NS("IOMMUFD");
MODULE_DESCRIPTION("I/O Address Space Management for passthrough devices");
MODULE_LICENSE("GPL");