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由 Guenter Roeck 提交于
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: NArkadiusz Miskiewicz <arekm@maven.pl> Signed-off-by: NGuenter Roeck <linux@roeck-us.net> Tested-by: NArkadiusz Miskiewicz <arekm@maven.pl> Signed-off-by: NWim Van Sebroeck <wim@iguana.be>
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