Hi.
This patch fixes a real problem on 3.8.x, .3.9.x. Possibly earlier stable
lines too but I only tested on 3.8 and 3.9.
Upstream patch applies fine to 3.8 and 3.9 stable lines.
Please add to the stable queue. Thanks.
commit 60403f7a4d9368d187f79cba5e4672d01df37574
Author: Guenter Roeck <linux@xxxxxxxxxxxx>
Date: Fri Apr 5 21:22:43 2013 -0700
watchdog: Fix race condition in registration code
A race condition exists when registering the first watchdog device.
Sequence of events:
- watchdog_register_device calls watchdog_dev_register
- watchdog_dev_register creates the watchdog misc device by calling
misc_register.
At that time, the matching character device (/dev/watchdog0) does not
yet
exist, and old_wdd is not set either.
- Userspace gets an event and opens /dev/watchdog
- watchdog_open is called and sets wdd = old_wdd, which is still NULL,
and tries to dereference it. This causes the kernel to panic.
Seen with systemd trying to open /dev/watchdog immediately after
it was created.
Reported-by: Arkadiusz Miskiewicz <arekm@xxxxxxxx>
Signed-off-by: Guenter Roeck <linux@xxxxxxxxxxxx>
Tested-by: Arkadiusz Miskiewicz <arekm@xxxxxxxx>
Signed-off-by: Wim Van Sebroeck <wim@xxxxxxxxx>
--
Arkadiusz Miśkiewicz, arekm / maven.pl
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