[PATCH] watchdog: at91sam9_wdt: prevent timer rearm during teardown

[PATCH] watchdog: at91sam9_wdt: prevent timer rearm during teardown

[Hongyan Xu]

at91_ping() rearms the watchdog timer from its callback. timer_delete()
neither waits for a running callback nor prevents it from rearming the
timer, so probe failure or driver removal can leave the timer accessing the
devm-allocated at91wdt after it has been freed.

Use timer_shutdown_sync() on both teardown paths. It waits for a running
callback and rejects any attempt by the callback to rearm the timer.

Fixes: 5161b31dc39a ("watchdog: at91sam9_wdt: better watchdog support")
Signed-off-by: Hongyan Xu <getshell@seu.edu.cn>
---
 drivers/watchdog/at91sam9_wdt.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/watchdog/at91sam9_wdt.c b/drivers/watchdog/at91sam9_wdt.c
index aba66b8e9d03..80ba04df54ad 100644
--- a/drivers/watchdog/at91sam9_wdt.c
+++ b/drivers/watchdog/at91sam9_wdt.c
@@ -242,7 +242,7 @@ static int at91_wdt_init(struct platform_device *pdev, struct at91wdt *wdt)
 	return 0;
 
 out_stop_timer:
-	timer_delete(&wdt->timer);
+	timer_shutdown_sync(&wdt->timer);
 	return err;
 }
 
@@ -378,7 +378,7 @@ static void at91wdt_remove(struct platform_device *pdev)
 	watchdog_unregister_device(&wdt->wdd);
 
 	pr_warn("I quit now, hardware will probably reboot!\n");
-	timer_delete(&wdt->timer);
+	timer_shutdown_sync(&wdt->timer);
 }
 
 #if defined(CONFIG_OF)
-- 
2.50.1.windows.1

Re: [PATCH] watchdog: at91sam9_wdt: prevent timer rearm during teardown

[Guenter Roeck]

On Thu, Aug 06, 2026 at 02:06:13PM +0800, Hongyan Xu wrote:
> at91_ping() rearms the watchdog timer from its callback. timer_delete()
> neither waits for a running callback nor prevents it from rearming the
> timer, so probe failure or driver removal can leave the timer accessing the
> devm-allocated at91wdt after it has been freed.
> 
> Use timer_shutdown_sync() on both teardown paths. It waits for a running
> callback and rejects any attempt by the callback to rearm the timer.
> 
> Fixes: 5161b31dc39a ("watchdog: at91sam9_wdt: better watchdog support")
> Signed-off-by: Hongyan Xu <getshell@seu.edu.cn>

Applied.

Thanks,
Guenter