From: Bartosz Golaszewski bartosz.golaszewski@linaro.org
[ Upstream commit bdbbae241a04f387ba910b8609f95fad5f1470c7 ]
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: d7c51b47ac11 ("gpio: userspace ABI for reading/writing GPIO lines") Fixes: 3c0d9c635ae2 ("gpiolib: cdev: support GPIO_V2_GET_LINE_IOCTL and GPIO_V2_LINE_GET_VALUES_IOCTL") Fixes: aad955842d1c ("gpiolib: cdev: support GPIO_V2_GET_LINEINFO_IOCTL and GPIO_V2_GET_LINEINFO_WATCH_IOCTL") Fixes: a54756cb24ea ("gpiolib: cdev: support GPIO_V2_LINE_SET_CONFIG_IOCTL") Fixes: 7b8e00d98168 ("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 Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/gpio/gpiolib-cdev.c | 177 +++++++++++++++++++++++++++++++----- drivers/gpio/gpiolib.c | 4 + drivers/gpio/gpiolib.h | 5 + 3 files changed, 161 insertions(+), 25 deletions(-)
diff --git a/drivers/gpio/gpiolib-cdev.c b/drivers/gpio/gpiolib-cdev.c index 6fa5c2169985..6ab1cf489d03 100644 --- a/drivers/gpio/gpiolib-cdev.c +++ b/drivers/gpio/gpiolib-cdev.c @@ -55,6 +55,50 @@ static_assert(IS_ALIGNED(sizeof(struct gpio_v2_line_values), 8)); * 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 */ @@ -191,8 +235,8 @@ static long linehandle_set_config(struct linehandle_state *lh, return 0; }
-static long linehandle_ioctl(struct file *file, unsigned int cmd, - unsigned long arg) +static long linehandle_ioctl_unlocked(struct file *file, unsigned int cmd, + unsigned long arg) { struct linehandle_state *lh = file->private_data; void __user *ip = (void __user *)arg; @@ -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 static long linehandle_ioctl_compat(struct file *file, unsigned int cmd, unsigned long arg) @@ -1381,8 +1434,8 @@ static long linereq_set_config(struct linereq *lr, void __user *ip) return ret; }
-static long linereq_ioctl(struct file *file, unsigned int cmd, - unsigned long arg) +static long linereq_ioctl_unlocked(struct file *file, unsigned int cmd, + unsigned long arg) { struct linereq *lr = file->private_data; void __user *ip = (void __user *)arg; @@ -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 static long linereq_ioctl_compat(struct file *file, unsigned int cmd, unsigned long arg) @@ -1410,8 +1472,8 @@ static long linereq_ioctl_compat(struct file *file, unsigned int cmd, } #endif
-static __poll_t linereq_poll(struct file *file, - struct poll_table_struct *wait) +static __poll_t linereq_poll_unlocked(struct file *file, + struct poll_table_struct *wait) { struct linereq *lr = file->private_data; __poll_t events = 0; @@ -1428,10 +1490,16 @@ static __poll_t linereq_poll(struct file *file, return events; }
-static ssize_t linereq_read(struct file *file, - char __user *buf, - size_t count, - loff_t *f_ps) +static __poll_t linereq_poll(struct file *file, + struct poll_table_struct *wait) +{ + 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 gpio_v2_line_event le; @@ -1485,6 +1553,15 @@ static ssize_t linereq_read(struct file *file, 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) { unsigned int i; @@ -1722,8 +1799,8 @@ struct lineevent_state { (GPIOEVENT_REQUEST_RISING_EDGE | \ GPIOEVENT_REQUEST_FALLING_EDGE)
-static __poll_t lineevent_poll(struct file *file, - struct poll_table_struct *wait) +static __poll_t lineevent_poll_unlocked(struct file *file, + struct poll_table_struct *wait) { struct lineevent_state *le = file->private_data; __poll_t events = 0; @@ -1739,15 +1816,21 @@ static __poll_t lineevent_poll(struct file *file, 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 { compat_u64 timestamp; u32 id; };
-static ssize_t lineevent_read(struct file *file, - char __user *buf, - size_t count, - loff_t *f_ps) +static ssize_t lineevent_read_unlocked(struct file *file, char __user *buf, + size_t count, loff_t *f_ps) { struct lineevent_state *le = file->private_data; struct gpioevent_data ge; @@ -1815,6 +1898,15 @@ static ssize_t lineevent_read(struct file *file, 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) { if (le->irq) @@ -1832,8 +1924,8 @@ static int lineevent_release(struct inode *inode, struct file *file) return 0; }
-static long lineevent_ioctl(struct file *file, unsigned int cmd, - unsigned long arg) +static long lineevent_ioctl_unlocked(struct file *file, unsigned int cmd, + unsigned long arg) { struct lineevent_state *le = file->private_data; void __user *ip = (void __user *)arg; @@ -1864,6 +1956,15 @@ static long lineevent_ioctl(struct file *file, unsigned int cmd, 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 static long lineevent_ioctl_compat(struct file *file, unsigned int cmd, unsigned long arg) @@ -2422,8 +2523,8 @@ static int lineinfo_changed_notify(struct notifier_block *nb, return NOTIFY_OK; }
-static __poll_t lineinfo_watch_poll(struct file *file, - struct poll_table_struct *pollt) +static __poll_t lineinfo_watch_poll_unlocked(struct file *file, + struct poll_table_struct *pollt) { struct gpio_chardev_data *cdev = file->private_data; __poll_t events = 0; @@ -2440,8 +2541,17 @@ static __poll_t lineinfo_watch_poll(struct file *file, return events; }
-static ssize_t lineinfo_watch_read(struct file *file, char __user *buf, - size_t count, loff_t *off) +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) { struct gpio_chardev_data *cdev = file->private_data; struct gpio_v2_line_info_changed event; @@ -2519,6 +2629,15 @@ static ssize_t lineinfo_watch_read(struct file *file, char __user *buf, 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 * @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; int ret = -ENOMEM;
+ down_read(&gdev->sem); + /* Fail on open if the backing gpiochip is gone */ - if (!gdev->chip) - return -ENODEV; + if (!gdev->chip) { + ret = -ENODEV; + goto out_unlock; + }
cdev = kzalloc(sizeof(*cdev), GFP_KERNEL); if (!cdev) - return -ENOMEM; + goto out_unlock;
cdev->watched_lines = bitmap_zalloc(gdev->chip->ngpio, GFP_KERNEL); if (!cdev->watched_lines) @@ -2561,6 +2684,8 @@ static int gpio_chrdev_open(struct inode *inode, struct file *file) if (ret) goto out_unregister_notifier;
+ up_read(&gdev->sem); + return ret;
out_unregister_notifier: @@ -2570,6 +2695,8 @@ static int gpio_chrdev_open(struct inode *inode, struct file *file) bitmap_free(cdev->watched_lines); out_free_cdev: kfree(cdev); +out_unlock: + up_read(&gdev->sem); return ret; }
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c index a70522aef355..5974cfc61b41 100644 --- a/drivers/gpio/gpiolib.c +++ b/drivers/gpio/gpiolib.c @@ -735,6 +735,7 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, void *data, spin_unlock_irqrestore(&gpio_lock, flags);
BLOCKING_INIT_NOTIFIER_HEAD(&gdev->notifier); + init_rwsem(&gdev->sem);
#ifdef CONFIG_PINCTRL INIT_LIST_HEAD(&gdev->pin_ranges); @@ -875,6 +876,8 @@ void gpiochip_remove(struct gpio_chip *gc) unsigned long flags; unsigned int i;
+ down_write(&gdev->sem); + /* FIXME: should the legacy sysfs handling be moved to gpio_device? */ gpiochip_sysfs_unregister(gdev); gpiochip_free_hogs(gc); @@ -909,6 +912,7 @@ void gpiochip_remove(struct gpio_chip *gc) * gone. */ gcdev_unregister(gdev); + up_write(&gdev->sem); put_device(&gdev->dev); } EXPORT_SYMBOL_GPL(gpiochip_remove); diff --git a/drivers/gpio/gpiolib.h b/drivers/gpio/gpiolib.h index d900ecdbac46..9ad68a0adf4a 100644 --- a/drivers/gpio/gpiolib.h +++ b/drivers/gpio/gpiolib.h @@ -15,6 +15,7 @@ #include <linux/device.h> #include <linux/module.h> #include <linux/cdev.h> +#include <linux/rwsem.h>
#define GPIOCHIP_NAME "gpiochip"
@@ -39,6 +40,9 @@ * @list: links gpio_device:s together for traversal * @notifier: used to notify subscribers about lines being requested, released * 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 * * This state container holds most of the runtime variable data @@ -60,6 +64,7 @@ struct gpio_device { void *data; struct list_head list; struct blocking_notifier_head notifier; + struct rw_semaphore sem;
#ifdef CONFIG_PINCTRL /*