public-mirrors/linux
1
0
Fork 0
mirror of git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git synced 2025-05-24 10:39:52 +00:00
Code Issues Projects Releases Packages Wiki Activity Actions
linux/kernel/bpf
History
Dave Marchevsky 06ab134ce8 bpf: Refcount task stack in bpf_get_task_stack 
On x86 the struct pt_regs * grabbed by task_pt_regs() points to an
offset of task->stack. The pt_regs are later dereferenced in
__bpf_get_stack (e.g. by user_mode() check). This can cause a fault if
the task in question exits while bpf_get_task_stack is executing, as
warned by task_stack_page's comment:

* When accessing the stack of a non-current task that might exit, use
* try_get_task_stack() instead.  task_stack_page will return a pointer
* that could get freed out from under you.

Taking the comment's advice and using try_get_task_stack() and
put_task_stack() to hold task->stack refcount, or bail early if it's
already 0. Incrementing stack_refcount will ensure the task's stack
sticks around while we're using its data.

I noticed this bug while testing a bpf task iter similar to
bpf_iter_task_stack in selftests, except mine grabbed user stack, and
getting intermittent crashes, which resulted in dumps like:

  BUG: unable to handle page fault for address: 0000000000003fe0
  \#PF: supervisor read access in kernel mode
  \#PF: error_code(0x0000) - not-present page
  RIP: 0010:__bpf_get_stack+0xd0/0x230
  <snip...>
  Call Trace:
  bpf_prog_0a2be35c092cb190_get_task_stacks+0x5d/0x3ec
  bpf_iter_run_prog+0x24/0x81
  __task_seq_show+0x58/0x80
  bpf_seq_read+0xf7/0x3d0
  vfs_read+0x91/0x140
  ksys_read+0x59/0xd0
  do_syscall_64+0x48/0x120
  entry_SYSCALL_64_after_hwframe+0x44/0xa9

Fixes: fa28dcb82a ("bpf: Introduce helper bpf_get_task_stack()")
Signed-off-by: Dave Marchevsky <davemarchevsky@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20210401000747.3648767-1-davemarchevsky@fb.com
2021-04-01 13:58:07 -07:00
..
preload bpf: Fix umd memory leak in copy_process() 2021-03-19 22:23:19 +01:00
arraymap.c bpf: Eliminate rlimit-based memory accounting for arraymap maps 2020-12-02 18:32:46 -08:00
bpf_inode_storage.c bpf: Change inode_storage's lookup_elem return value from NULL to -EBADF 2021-03-08 16:08:06 +01:00
bpf_iter.c bpf: Fix an unitialized value in bpf_iter 2021-02-12 13:33:50 -08:00
bpf_local_storage.c bpf: Eliminate rlimit-based memory accounting for bpf local storage maps 2020-12-02 18:32:47 -08:00
bpf_lru_list.c bpf_lru_list: Read double-checked variable once without lock 2021-02-10 15:54:26 -08:00
bpf_lru_list.h bpf: Fix a typo "inacitve" -> "inactive" 2020-04-06 21:54:10 +02:00
bpf_lsm.c bpf: Drop disabled LSM hooks from the sleepable set 2021-01-26 17:08:50 +01:00
bpf_struct_ops.c bpf: Fix fexit trampoline. 2021-03-18 00:22:51 +01:00
bpf_struct_ops_types.h bpf: tcp: Support tcp_congestion_ops in bpf 2020-01-09 08:46:18 -08:00
bpf_task_storage.c bpf: Local storage helpers should check nullness of owner ptr passed 2021-01-12 16:07:56 +01:00
btf.c bpf: Drop imprecise log message 2021-02-24 16:43:39 +01:00
cgroup.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next 2021-02-16 13:14:06 -08:00
core.c bpf: Fix fexit trampoline. 2021-03-18 00:22:51 +01:00
cpumap.c net, xdp: Introduce __xdp_build_skb_from_frame utility routine 2021-01-20 14:10:35 -08:00
devmap.c bpf, devmap: Use GFP_KERNEL for xdp bulk queue allocation 2021-02-13 00:11:26 +01:00
disasm.c bpf: Fix a spelling typo in bpf_atomic_alu_string disasm 2021-03-26 17:56:48 +01:00
disasm.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 295 2019-06-05 17:36:38 +02:00
dispatcher.c bpf: Remove bpf_image tree 2020-03-13 12:49:52 -07:00
hashtab.c bpf: Allows per-cpu maps and map-in-map in sleepable programs 2021-02-11 16:19:26 +01:00
helpers.c bpf: Simplify cases in bpf_base_func_proto 2021-01-29 02:20:28 +01:00
inode.c fs: make helpers idmap mount aware 2021-01-24 14:27:20 +01:00
local_storage.c bpf: Eliminate rlimit-based memory accounting for cgroup storage maps 2020-12-02 18:32:46 -08:00
lpm_trie.c bpf: Eliminate rlimit-based memory accounting for lpm_trie maps 2020-12-02 18:32:46 -08:00
Makefile Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next 2020-11-14 09:13:41 -08:00
map_in_map.c bpf: Relax max_entries check for most of the inner map types 2020-08-28 15:41:30 +02:00
map_in_map.h bpf: Add map_meta_equal map ops 2020-08-28 15:41:30 +02:00
map_iter.c bpf: Implement link_query callbacks in map element iterators 2020-08-21 14:01:39 -07:00
net_namespace.c bpf: Add support for forced LINK_DETACH command 2020-08-01 20:38:28 -07:00
offload.c bpf, offload: Replace bitwise AND by logical AND in bpf_prog_offload_info_fill 2020-02-17 16:53:49 +01:00
percpu_freelist.c bpf: Use raw_spin_trylock() for pcpu_freelist_push/pop in NMI 2020-10-06 00:04:11 +02:00
percpu_freelist.h bpf: Use raw_spin_trylock() for pcpu_freelist_push/pop in NMI 2020-10-06 00:04:11 +02:00
prog_iter.c bpf: Refactor bpf_iter_reg to have separate seq_info member 2020-07-25 20:16:32 -07:00
queue_stack_maps.c bpf: Eliminate rlimit-based memory accounting for queue_stack_maps maps 2020-12-02 18:32:46 -08:00
reuseport_array.c bpf: Eliminate rlimit-based memory accounting for reuseport_array maps 2020-12-02 18:32:47 -08:00
ringbuf.c bpf: Eliminate rlimit-based memory accounting for bpf ringbuffer 2020-12-02 18:32:47 -08:00
stackmap.c bpf: Refcount task stack in bpf_get_task_stack 2021-04-01 13:58:07 -07:00
syscall.c bpf: Dont allow vmlinux BTF to be used in map_create and prog_load. 2021-03-08 13:32:46 +01:00
sysfs_btf.c bpf: Load and verify kernel module BTFs 2020-11-10 15:25:53 -08:00
task_iter.c bpf: Introduce task_vma bpf_iter 2021-02-12 12:56:53 -08:00
tnum.c bpf: Verifier, do explicit ALU32 bounds tracking 2020-03-30 14:59:53 -07:00
trampoline.c bpf: Take module reference for trampoline in module 2021-03-26 19:30:11 -07:00
verifier.c bpf: Enforce that struct_ops programs be GPL-only 2021-03-26 17:50:39 +01:00