From: Guenter Roeck Date: Sat, 6 Apr 2013 04:22:43 +0000 (-0700) Subject: watchdog: Fix race condition in registration code X-Git-Tag: v3.10-rc1~39^2 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=60403f7a4d9368d187f79cba5e4672d01df37574;p=pandora-kernel.git 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 Signed-off-by: Guenter Roeck Tested-by: Arkadiusz Miskiewicz Signed-off-by: Wim Van Sebroeck --- Reading git-diff-tree failed