A reboot notifier, which stops the WDT by calling the stop hook without
any check, would be registered when we set WDOG_STOP_ON_REBOOT flag.
Howerer we allow the WDT driver to omit the stop hook since commit
"d0684c8a93549" ("watchdog: Make stop function optional") and provide
a module parameter for user that controls the WDOG_STOP_ON_REBOOT flag
in commit 9232c80659e94 ("watchdog: Add stop_on_reboot parameter to
control reboot policy"). Together that commits make user potential to
insert a watchdog driver that don't provide a stop hook but with the
stop_on_reboot parameter set, then dereferencing of null pointer occurs
on system reboot.
Check the stop hook before registering the reboot notifier to fix the
issue.
Signed-off-by: Wang Wensheng <wangwensheng4@xxxxxxxxxx>
---
drivers/watchdog/watchdog_core.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/drivers/watchdog/watchdog_core.c b/drivers/watchdog/watchdog_core.c
index c73871f41142..5269761ba072 100644
--- a/drivers/watchdog/watchdog_core.c
+++ b/drivers/watchdog/watchdog_core.c
@@ -265,8 +265,12 @@ static int __watchdog_register_device(struct watchdog_device *wdd)
}
if (test_bit(WDOG_STOP_ON_REBOOT, &wdd->status)) {
- wdd->reboot_nb.notifier_call = watchdog_reboot_notifier;
+ if (!wdd->ops->stop) {
+ ret = -EINVAL;
+ goto dev_unregister;
+ }
+ wdd->reboot_nb.notifier_call = watchdog_reboot_notifier;
ret = register_reboot_notifier(&wdd->reboot_nb);
if (ret) {
pr_err("watchdog%d: Cannot register reboot notifier (%d)\n",
--
2.25.0
