diff options
| author | Kent Gibson <warthog618@gmail.com> | 2020-07-08 12:15:53 +0800 |
|---|---|---|
| committer | Bartosz Golaszewski <bgolaszewski@baylibre.com> | 2020-07-12 10:22:01 +0200 |
| commit | f30ef3e8376380c5be9de121517c713527cf0813 (patch) | |
| tree | aa8a58adb18e33acaab8db518e5fb4ec6030e448 | |
| parent | e2b781c5f0dd45f632b3e15bbca702d1d140fce7 (diff) | |
gpiolib: cdev: fix minor race in GET_LINEINFO_WATCH
Merge separate usage of test_bit/set_bit into test_and_set_bit to remove
the possibility of a race between the test and set.
Similarly test_bit and clear_bit.
In the existing code it is possible for two threads to race past the
test_bit and then set or clear the watch bit, and neither return EBUSY.
Signed-off-by: Kent Gibson <warthog618@gmail.com>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
| -rw-r--r-- | drivers/gpio/gpiolib-cdev.c | 10 |
1 files changed, 5 insertions, 5 deletions
diff --git a/drivers/gpio/gpiolib-cdev.c b/drivers/gpio/gpiolib-cdev.c index fe1b385deecc..b2b26dc25051 100644 --- a/drivers/gpio/gpiolib-cdev.c +++ b/drivers/gpio/gpiolib-cdev.c @@ -887,15 +887,16 @@ static long gpio_ioctl(struct file *file, unsigned int cmd, unsigned long arg) hwgpio = gpio_chip_hwgpio(desc); - if (test_bit(hwgpio, cdev->watched_lines)) + if (test_and_set_bit(hwgpio, cdev->watched_lines)) return -EBUSY; gpio_desc_to_lineinfo(desc, &lineinfo); - if (copy_to_user(ip, &lineinfo, sizeof(lineinfo))) + if (copy_to_user(ip, &lineinfo, sizeof(lineinfo))) { + clear_bit(hwgpio, cdev->watched_lines); return -EFAULT; + } - set_bit(hwgpio, cdev->watched_lines); return 0; } else if (cmd == GPIO_GET_LINEINFO_UNWATCH_IOCTL) { if (copy_from_user(&offset, ip, sizeof(offset))) @@ -907,10 +908,9 @@ static long gpio_ioctl(struct file *file, unsigned int cmd, unsigned long arg) hwgpio = gpio_chip_hwgpio(desc); - if (!test_bit(hwgpio, cdev->watched_lines)) + if (!test_and_clear_bit(hwgpio, cdev->watched_lines)) return -EBUSY; - clear_bit(hwgpio, cdev->watched_lines); return 0; } return -EINVAL; |