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gpiolib: protect the GPIO device against being dropped while in use by user-space

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While any of the GPIO cdev syscalls is in progress, the kernel can call
gpiochip_remove() (for instance, when a USB GPIO expander is disconnected)
which will set gdev->chip to NULL after which any subsequent access will
cause a crash.

To avoid that: use an RW-semaphore in which the syscalls take it for
reading (so that we don't needlessly prohibit the user-space from calling
syscalls simultaneously) while gpiochip_remove() takes it for writing so
that it can only happen once all syscalls return.

Fixes: d7c51b47ac ("gpio: userspace ABI for reading/writing GPIO lines")
Fixes: 3c0d9c635a ("gpiolib: cdev: support GPIO_V2_GET_LINE_IOCTL and GPIO_V2_LINE_GET_VALUES_IOCTL")
Fixes: aad955842d ("gpiolib: cdev: support GPIO_V2_GET_LINEINFO_IOCTL and GPIO_V2_GET_LINEINFO_WATCH_IOCTL")
Fixes: a54756cb24 ("gpiolib: cdev: support GPIO_V2_LINE_SET_CONFIG_IOCTL")
Fixes: 7b8e00d981 ("gpiolib: cdev: support GPIO_V2_LINE_SET_VALUES_IOCTL")
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
[Nick: fixed a build failure with CDEV_V1 disabled]
Co-authored-by: Nick Hainke <vincent@systemli.org>
Reviewed-by: Kent Gibson <warthog618@gmail.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
This commit is contained in:
Bartosz Golaszewski 2022-12-05 13:39:03 +01:00
parent 533aae7c94
commit bdbbae241a
3 changed files with 161 additions and 25 deletions
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163
drivers/gpio/gpiolib-cdev.c
View file

@ -55,6 +55,50 @@ static_assert(IS_ALIGNED(sizeof(struct gpio_v2_line_values), 8));
* interface to gpiolib GPIOs via ioctl()s. * interface to gpiolib GPIOs via ioctl()s.
*/ */
typedef __poll_t (*poll_fn)(struct file *, struct poll_table_struct *);
typedef long (*ioctl_fn)(struct file *, unsigned int, unsigned long);
typedef ssize_t (*read_fn)(struct file *, char __user *,
size_t count, loff_t *);
static __poll_t call_poll_locked(struct file *file,
struct poll_table_struct *wait,
struct gpio_device *gdev, poll_fn func)
{
__poll_t ret;
down_read(&gdev->sem);
ret = func(file, wait);
up_read(&gdev->sem);
return ret;
}
static long call_ioctl_locked(struct file *file, unsigned int cmd,
unsigned long arg, struct gpio_device *gdev,
ioctl_fn func)
{
long ret;
down_read(&gdev->sem);
ret = func(file, cmd, arg);
up_read(&gdev->sem);
return ret;
}
static ssize_t call_read_locked(struct file *file, char __user *buf,
size_t count, loff_t *f_ps,
struct gpio_device *gdev, read_fn func)
{
ssize_t ret;
down_read(&gdev->sem);
ret = func(file, buf, count, f_ps);
up_read(&gdev->sem);
return ret;
}
/* /*
* GPIO line handle management * GPIO line handle management
*/ */
@ -191,7 +235,7 @@ static long linehandle_set_config(struct linehandle_state *lh,
return 0; return 0;
} }
static long linehandle_ioctl(struct file *file, unsigned int cmd, static long linehandle_ioctl_unlocked(struct file *file, unsigned int cmd,
unsigned long arg) unsigned long arg)
{ {
struct linehandle_state *lh = file->private_data; struct linehandle_state *lh = file->private_data;
@ -250,6 +294,15 @@ static long linehandle_ioctl(struct file *file, unsigned int cmd,
} }
} }
static long linehandle_ioctl(struct file *file, unsigned int cmd,
unsigned long arg)
{
struct linehandle_state *lh = file->private_data;
return call_ioctl_locked(file, cmd, arg, lh->gdev,
linehandle_ioctl_unlocked);
}
#ifdef CONFIG_COMPAT #ifdef CONFIG_COMPAT
static long linehandle_ioctl_compat(struct file *file, unsigned int cmd, static long linehandle_ioctl_compat(struct file *file, unsigned int cmd,
unsigned long arg) unsigned long arg)
@ -1381,7 +1434,7 @@ static long linereq_set_config(struct linereq *lr, void __user *ip)
return ret; return ret;
} }
static long linereq_ioctl(struct file *file, unsigned int cmd, static long linereq_ioctl_unlocked(struct file *file, unsigned int cmd,
unsigned long arg) unsigned long arg)
{ {
struct linereq *lr = file->private_data; struct linereq *lr = file->private_data;
@ -1402,6 +1455,15 @@ static long linereq_ioctl(struct file *file, unsigned int cmd,
} }
} }
static long linereq_ioctl(struct file *file, unsigned int cmd,
unsigned long arg)
{
struct linereq *lr = file->private_data;
return call_ioctl_locked(file, cmd, arg, lr->gdev,
linereq_ioctl_unlocked);
}
#ifdef CONFIG_COMPAT #ifdef CONFIG_COMPAT
static long linereq_ioctl_compat(struct file *file, unsigned int cmd, static long linereq_ioctl_compat(struct file *file, unsigned int cmd,
unsigned long arg) unsigned long arg)
@ -1410,7 +1472,7 @@ static long linereq_ioctl_compat(struct file *file, unsigned int cmd,
} }
#endif #endif
static __poll_t linereq_poll(struct file *file, static __poll_t linereq_poll_unlocked(struct file *file,
struct poll_table_struct *wait) struct poll_table_struct *wait)
{ {
struct linereq *lr = file->private_data; struct linereq *lr = file->private_data;
@ -1428,10 +1490,16 @@ static __poll_t linereq_poll(struct file *file,
return events; return events;
} }
static ssize_t linereq_read(struct file *file, static __poll_t linereq_poll(struct file *file,
char __user *buf, struct poll_table_struct *wait)
size_t count, {
loff_t *f_ps) struct linereq *lr = file->private_data;
return call_poll_locked(file, wait, lr->gdev, linereq_poll_unlocked);
}
static ssize_t linereq_read_unlocked(struct file *file, char __user *buf,
size_t count, loff_t *f_ps)
{ {
struct linereq *lr = file->private_data; struct linereq *lr = file->private_data;
struct gpio_v2_line_event le; struct gpio_v2_line_event le;
@ -1485,6 +1553,15 @@ static ssize_t linereq_read(struct file *file,
return bytes_read; return bytes_read;
} }
static ssize_t linereq_read(struct file *file, char __user *buf,
size_t count, loff_t *f_ps)
{
struct linereq *lr = file->private_data;
return call_read_locked(file, buf, count, f_ps, lr->gdev,
linereq_read_unlocked);
}
static void linereq_free(struct linereq *lr) static void linereq_free(struct linereq *lr)
{ {
unsigned int i; unsigned int i;
@ -1722,7 +1799,7 @@ struct lineevent_state {
(GPIOEVENT_REQUEST_RISING_EDGE | \ (GPIOEVENT_REQUEST_RISING_EDGE | \
GPIOEVENT_REQUEST_FALLING_EDGE) GPIOEVENT_REQUEST_FALLING_EDGE)
static __poll_t lineevent_poll(struct file *file, static __poll_t lineevent_poll_unlocked(struct file *file,
struct poll_table_struct *wait) struct poll_table_struct *wait)
{ {
struct lineevent_state *le = file->private_data; struct lineevent_state *le = file->private_data;
@ -1739,15 +1816,21 @@ static __poll_t lineevent_poll(struct file *file,
return events; return events;
} }
static __poll_t lineevent_poll(struct file *file,
struct poll_table_struct *wait)
{
struct lineevent_state *le = file->private_data;
return call_poll_locked(file, wait, le->gdev, lineevent_poll_unlocked);
}
struct compat_gpioeevent_data { struct compat_gpioeevent_data {
compat_u64 timestamp; compat_u64 timestamp;
u32 id; u32 id;
}; };
static ssize_t lineevent_read(struct file *file, static ssize_t lineevent_read_unlocked(struct file *file, char __user *buf,
char __user *buf, size_t count, loff_t *f_ps)
size_t count,
loff_t *f_ps)
{ {
struct lineevent_state *le = file->private_data; struct lineevent_state *le = file->private_data;
struct gpioevent_data ge; struct gpioevent_data ge;
@ -1815,6 +1898,15 @@ static ssize_t lineevent_read(struct file *file,
return bytes_read; return bytes_read;
} }
static ssize_t lineevent_read(struct file *file, char __user *buf,
size_t count, loff_t *f_ps)
{
struct lineevent_state *le = file->private_data;
return call_read_locked(file, buf, count, f_ps, le->gdev,
lineevent_read_unlocked);
}
static void lineevent_free(struct lineevent_state *le) static void lineevent_free(struct lineevent_state *le)
{ {
if (le->irq) if (le->irq)
@ -1832,7 +1924,7 @@ static int lineevent_release(struct inode *inode, struct file *file)
return 0; return 0;
} }
static long lineevent_ioctl(struct file *file, unsigned int cmd, static long lineevent_ioctl_unlocked(struct file *file, unsigned int cmd,
unsigned long arg) unsigned long arg)
{ {
struct lineevent_state *le = file->private_data; struct lineevent_state *le = file->private_data;
@ -1864,6 +1956,15 @@ static long lineevent_ioctl(struct file *file, unsigned int cmd,
return -EINVAL; return -EINVAL;
} }
static long lineevent_ioctl(struct file *file, unsigned int cmd,
unsigned long arg)
{
struct lineevent_state *le = file->private_data;
return call_ioctl_locked(file, cmd, arg, le->gdev,
lineevent_ioctl_unlocked);
}
#ifdef CONFIG_COMPAT #ifdef CONFIG_COMPAT
static long lineevent_ioctl_compat(struct file *file, unsigned int cmd, static long lineevent_ioctl_compat(struct file *file, unsigned int cmd,
unsigned long arg) unsigned long arg)
@ -2422,7 +2523,7 @@ static int lineinfo_changed_notify(struct notifier_block *nb,
return NOTIFY_OK; return NOTIFY_OK;
} }
static __poll_t lineinfo_watch_poll(struct file *file, static __poll_t lineinfo_watch_poll_unlocked(struct file *file,
struct poll_table_struct *pollt) struct poll_table_struct *pollt)
{ {
struct gpio_chardev_data *cdev = file->private_data; struct gpio_chardev_data *cdev = file->private_data;
@ -2440,7 +2541,16 @@ static __poll_t lineinfo_watch_poll(struct file *file,
return events; return events;
} }
static ssize_t lineinfo_watch_read(struct file *file, char __user *buf, static __poll_t lineinfo_watch_poll(struct file *file,
struct poll_table_struct *pollt)
{
struct gpio_chardev_data *cdev = file->private_data;
return call_poll_locked(file, pollt, cdev->gdev,
lineinfo_watch_poll_unlocked);
}
static ssize_t lineinfo_watch_read_unlocked(struct file *file, char __user *buf,
size_t count, loff_t *off) size_t count, loff_t *off)
{ {
struct gpio_chardev_data *cdev = file->private_data; struct gpio_chardev_data *cdev = file->private_data;
@ -2519,6 +2629,15 @@ static ssize_t lineinfo_watch_read(struct file *file, char __user *buf,
return bytes_read; return bytes_read;
} }
static ssize_t lineinfo_watch_read(struct file *file, char __user *buf,
size_t count, loff_t *off)
{
struct gpio_chardev_data *cdev = file->private_data;
return call_read_locked(file, buf, count, off, cdev->gdev,
lineinfo_watch_read_unlocked);
}
/** /**
* gpio_chrdev_open() - open the chardev for ioctl operations * gpio_chrdev_open() - open the chardev for ioctl operations
* @inode: inode for this chardev * @inode: inode for this chardev
@ -2532,13 +2651,17 @@ static int gpio_chrdev_open(struct inode *inode, struct file *file)
struct gpio_chardev_data *cdev; struct gpio_chardev_data *cdev;
int ret = -ENOMEM; int ret = -ENOMEM;
down_read(&gdev->sem);
/* Fail on open if the backing gpiochip is gone */ /* Fail on open if the backing gpiochip is gone */
if (!gdev->chip) if (!gdev->chip) {
return -ENODEV; ret = -ENODEV;
goto out_unlock;
}
cdev = kzalloc(sizeof(*cdev), GFP_KERNEL); cdev = kzalloc(sizeof(*cdev), GFP_KERNEL);
if (!cdev) if (!cdev)
return -ENOMEM; goto out_unlock;
cdev->watched_lines = bitmap_zalloc(gdev->chip->ngpio, GFP_KERNEL); cdev->watched_lines = bitmap_zalloc(gdev->chip->ngpio, GFP_KERNEL);
if (!cdev->watched_lines) if (!cdev->watched_lines)
@ -2561,6 +2684,8 @@ static int gpio_chrdev_open(struct inode *inode, struct file *file)
if (ret) if (ret)
goto out_unregister_notifier; goto out_unregister_notifier;
up_read(&gdev->sem);
return ret; return ret;
out_unregister_notifier: out_unregister_notifier:
@ -2570,6 +2695,8 @@ out_free_bitmap:
bitmap_free(cdev->watched_lines); bitmap_free(cdev->watched_lines);
out_free_cdev: out_free_cdev:
kfree(cdev); kfree(cdev);
out_unlock:
up_read(&gdev->sem);
return ret; return ret;
} }

4
drivers/gpio/gpiolib.c
View file

@ -790,6 +790,7 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, void *data,
spin_unlock_irqrestore(&gpio_lock, flags); spin_unlock_irqrestore(&gpio_lock, flags);
BLOCKING_INIT_NOTIFIER_HEAD(&gdev->notifier); BLOCKING_INIT_NOTIFIER_HEAD(&gdev->notifier);
init_rwsem(&gdev->sem);
#ifdef CONFIG_PINCTRL #ifdef CONFIG_PINCTRL
INIT_LIST_HEAD(&gdev->pin_ranges); INIT_LIST_HEAD(&gdev->pin_ranges);
@ -924,6 +925,8 @@ void gpiochip_remove(struct gpio_chip *gc)
unsigned long flags; unsigned long flags;
unsigned int i; unsigned int i;
down_write(&gdev->sem);
/* FIXME: should the legacy sysfs handling be moved to gpio_device? */ /* FIXME: should the legacy sysfs handling be moved to gpio_device? */
gpiochip_sysfs_unregister(gdev); gpiochip_sysfs_unregister(gdev);
gpiochip_free_hogs(gc); gpiochip_free_hogs(gc);
@ -958,6 +961,7 @@ void gpiochip_remove(struct gpio_chip *gc)
* gone. * gone.
*/ */
gcdev_unregister(gdev); gcdev_unregister(gdev);
up_write(&gdev->sem);
put_device(&gdev->dev); put_device(&gdev->dev);
} }
EXPORT_SYMBOL_GPL(gpiochip_remove); EXPORT_SYMBOL_GPL(gpiochip_remove);

5
drivers/gpio/gpiolib.h
View file

@ -15,6 +15,7 @@
#include <linux/device.h> #include <linux/device.h>
#include <linux/module.h> #include <linux/module.h>
#include <linux/cdev.h> #include <linux/cdev.h>
#include <linux/rwsem.h>
#define GPIOCHIP_NAME "gpiochip" #define GPIOCHIP_NAME "gpiochip"
@ -39,6 +40,9 @@
* @list: links gpio_device:s together for traversal * @list: links gpio_device:s together for traversal
* @notifier: used to notify subscribers about lines being requested, released * @notifier: used to notify subscribers about lines being requested, released
* or reconfigured * or reconfigured
* @sem: protects the structure from a NULL-pointer dereference of @chip by
* user-space operations when the device gets unregistered during
* a hot-unplug event
* @pin_ranges: range of pins served by the GPIO driver * @pin_ranges: range of pins served by the GPIO driver
* *
* This state container holds most of the runtime variable data * This state container holds most of the runtime variable data
@ -60,6 +64,7 @@ struct gpio_device {
void *data; void *data;
struct list_head list; struct list_head list;
struct blocking_notifier_head notifier; struct blocking_notifier_head notifier;
struct rw_semaphore sem;
#ifdef CONFIG_PINCTRL #ifdef CONFIG_PINCTRL
/* /*