diff options
| author | Guenter Roeck <linux@roeck-us.net> | 2013-04-05 21:22:43 -0700 |
|---|---|---|
| committer | Luis Henriques <luis.henriques@canonical.com> | 2013-05-20 10:25:23 +0100 |
| commit | ff90ca92d7463bada0dc0fb53fcd765158d24592 (patch) | |
| tree | 0bde26955f59a1b94aeaea5520cd7a25ce1cdaa2 | |
| parent | 88e945d409bfd588b823805f9667c86fc324d069 (diff) | |
watchdog: Fix race condition in registration code
commit 60403f7a4d9368d187f79cba5e4672d01df37574 upstream.
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@maven.pl>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Tested-by: Arkadiusz Miskiewicz <arekm@maven.pl>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
| -rw-r--r-- | drivers/watchdog/watchdog_dev.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/drivers/watchdog/watchdog_dev.c b/drivers/watchdog/watchdog_dev.c index ef8edecfc526..05a531052591 100644 --- a/drivers/watchdog/watchdog_dev.c +++ b/drivers/watchdog/watchdog_dev.c @@ -524,6 +524,7 @@ int watchdog_dev_register(struct watchdog_device *watchdog) int err, devno; if (watchdog->id == 0) { + old_wdd = watchdog; watchdog_miscdev.parent = watchdog->parent; err = misc_register(&watchdog_miscdev); if (err != 0) { @@ -532,9 +533,9 @@ int watchdog_dev_register(struct watchdog_device *watchdog) if (err == -EBUSY) pr_err("%s: a legacy watchdog module is probably present.\n", watchdog->info->identity); + old_wdd = NULL; return err; } - old_wdd = watchdog; } /* Fill in the data structures */ |