From: Kent Gibson <warthog618@gmail.com>
To: linux-kernel@vger.kernel.org, linux-gpio@vger.kernel.org,
bgolaszewski@baylibre.com, linus.walleij@linaro.org
Cc: Kent Gibson <warthog618@gmail.com>
Subject: [PATCH 10/17] gpiolib: cdev: fix minor race in GET_LINEINFO_WATCH
Date: Wed, 8 Jul 2020 12:15:53 +0800 [thread overview]
Message-ID: <20200708041600.768775-11-warthog618@gmail.com> (raw)
In-Reply-To: <20200708041600.768775-1-warthog618@gmail.com>
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>
---
drivers/gpio/gpiolib-cdev.c | 10 +++++-----
1 file 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;
--
2.27.0
next prev parent reply other threads:[~2020-07-08 4:19 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-08 4:15 [PATCH 00/17] gpiolib: cdev: pre-uAPI v2 cleanups Kent Gibson
2020-07-08 4:15 ` [PATCH 01/17] gpiolib: move gpiolib-sysfs function declarations into their own header Kent Gibson
2020-07-08 4:15 ` [PATCH 02/17] gpiolib: cdev: sort includes Kent Gibson
2020-07-08 4:15 ` [PATCH 03/17] gpiolib: cdev: minor indentation fixes Kent Gibson
2020-07-08 4:15 ` [PATCH 04/17] gpiolib: cdev: refactor gpiohandle_flags_to_desc_flags Kent Gibson
2020-07-08 4:15 ` [PATCH 05/17] gpiolib: cdev: rename 'filep' and 'filp' to 'file' to be consistent with other use Kent Gibson
2020-07-08 4:15 ` [PATCH 06/17] gpiolib: cdev: rename numdescs to num_descs Kent Gibson
2020-07-08 4:15 ` [PATCH 07/17] gpiolib: cdev: remove pointless decrement of i Kent Gibson
2020-07-08 4:15 ` [PATCH 08/17] gpiolib: cdev: use blocking notifier call chain instead of atomic Kent Gibson
2020-07-09 10:06 ` Bartosz Golaszewski
2020-07-08 4:15 ` [PATCH 09/17] gpiolib: cdev: rename priv to cdev Kent Gibson
2020-07-08 4:15 ` Kent Gibson [this message]
2020-07-08 4:15 ` [PATCH 11/17] gpiolib: cdev: remove recalculation of offset Kent Gibson
2020-07-08 4:15 ` [PATCH 12/17] gpiolib: cdev: refactor linehandle cleanup into linehandle_free Kent Gibson
2020-07-08 4:15 ` [PATCH 13/17] gpiolib: cdev: refactor lineevent cleanup into lineevent_free Kent Gibson
2020-07-08 4:15 ` [PATCH 14/17] gpio: uapi: fix misplaced comment line Kent Gibson
2020-07-08 4:15 ` [PATCH 15/17] tools: gpio: fix spurious close warning in lsgpio Kent Gibson
2020-07-08 4:15 ` [PATCH 16/17] tools: gpio: fix spurious close warning in gpio-utils Kent Gibson
2020-07-08 4:16 ` [PATCH 17/17] tools: gpio: fix spurious close warning in gpio-event-mon Kent Gibson
2020-07-09 13:19 ` [PATCH 00/17] gpiolib: cdev: pre-uAPI v2 cleanups Bartosz Golaszewski
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