gpiolib: cdev: fix minor race in GET_LINEINFO_WATCH (f30ef3e8) · Commits · 戴 / test

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>

drivers/gpio/gpiolib-cdev.c

+5 −5

Original line number	Diff line number	Diff line
		@@ -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;

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