From: Wang Wensheng wangwensheng4@huawei.com
[ Upstream commit 6f733cb2e7db38f8141b14740bcde577844a03b7 ]
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.
Fixes: d0684c8a9354 ("watchdog: Make stop function optional") Signed-off-by: Wang Wensheng wangwensheng4@huawei.com Reviewed-by: Guenter Roeck linux@roeck-us.net Link: https://lore.kernel.org/r/20201109130512.28121-1-wangwensheng4@huawei.com Signed-off-by: Guenter Roeck linux@roeck-us.net Signed-off-by: Wim Van Sebroeck wim@linux-watchdog.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/watchdog/watchdog_core.c | 22 +++++++++++++--------- 1 file changed, 13 insertions(+), 9 deletions(-)
diff --git a/drivers/watchdog/watchdog_core.c b/drivers/watchdog/watchdog_core.c index 861daf4f37b28..faa46a666f4c5 100644 --- a/drivers/watchdog/watchdog_core.c +++ b/drivers/watchdog/watchdog_core.c @@ -255,15 +255,19 @@ 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; - - ret = register_reboot_notifier(&wdd->reboot_nb); - if (ret) { - pr_err("watchdog%d: Cannot register reboot notifier (%d)\n", - wdd->id, ret); - watchdog_dev_unregister(wdd); - ida_simple_remove(&watchdog_ida, id); - return ret; + if (!wdd->ops->stop) + pr_warn("watchdog%d: stop_on_reboot not supported\n", wdd->id); + else { + 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", + wdd->id, ret); + watchdog_dev_unregister(wdd); + ida_simple_remove(&watchdog_ida, id); + return ret; + } } }