FAILED: patch "[PATCH] tty: serial: max3100: shut down timer before freeing port" failed to apply to 6.1-stable tree

The patch below does not apply to the 6.1-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y
git checkout FETCH_HEAD
git cherry-pick -x db0949bbd06db0a75b4b1076f1e25194be7d956a
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026100500-tipper-geologic-7516@gregkh' --subject-prefix 'PATCH 6.1.y' 'HEAD^..'

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From db0949bbd06db0a75b4b1076f1e25194be7d956a Mon Sep 17 00:00:00 2001
From: Fan Wu <[email protected]>
Date: Sun, 27 Sep 2026 05:59:57 +0000
Subject: [PATCH] tty: serial: max3100: shut down timer before freeing port

max3100_shutdown() stops the polling timer but returns early during system suspend. If the SPI device is unbound before resume, the serial core does not call max3100_shutdown() again, so max3100_remove() frees the port while the timer remains armed. max3100_timeout() may then access the freed port and re-arm the timer.

Add final timer teardown to max3100_remove() and use timer_shutdown_sync() to prevent a racing callback from re-arming it. Also free the IRQ and destroy the workqueue there before freeing the port. Keep timer_delete_sync() in max3100_shutdown() so that a subsequent open() can re-arm the timer.

The workqueue is created before request_irq() and destroyed on both request_irq() failure and normal shutdown. Its presence at remove thus identifies the IRQ left registered when suspend bypasses shutdown.

Free the IRQ before destroying the workqueue, in both max3100_shutdown() and max3100_remove(), and cancel the pending work in between. free_irq() waits for a running interrupt handler to finish and no new handler can start afterwards, so a racing handler cannot queue work on a workqueue that is being destroyed; the force_end_work check in max3100_dowork() only narrows that window, as a handler delayed between the check and queue_work() could still run after the teardown has cleared the workqueue pointer. Cancelling the work also keeps destroy_workqueue() from waiting on a queued work item in case remove() ever runs while the freezable workqueue is still frozen, e.g. device removal during the resume window, before workqueues are thawed.

This issue was found by an in-house static analysis tool.

index a5a5cd68f696..f858a6669011 100644
@@ -535,11 +535,11 @@ static void max3100_shutdown(struct uart_port *port)
 	timer_delete_sync(&s->timer);
 
 	if (s->workqueue) {
+		free_irq(port->irq, s);
+		cancel_work_sync(&s->work);
 		destroy_workqueue(s->workqueue);
 		s->workqueue = NULL;
 	}
-	if (port->irq)
-		free_irq(port->irq, s);
 
 	/* set shutdown mode to save power */
 	max3100_sr(s, MAX3100_WC | MAX3100_SHDN, &rx);

@@ -753,6 +753,15 @@ static void max3100_remove(struct spi_device *spi)
 		if (max3100s[i] == s) {
 			dev_dbg(&spi->dev, "%s: removing port %d\n", __func__, i);
 			uart_remove_one_port(&max3100_uart_driver, &max3100s[i]->port);
+
+			s->force_end_work = 1;
+			timer_shutdown_sync(&s->timer);
+			if (s->workqueue) {
+				free_irq(s->port.irq, s);
+				cancel_work_sync(&s->work);
+				destroy_workqueue(s->workqueue);
+				s->workqueue = NULL;
+			}
 			kfree(max3100s[i]);
 			max3100s[i] = NULL;
 			break;

From: Fan Wu <[email protected]>

[ Upstream commit db0949bbd06db0a75b4b1076f1e25194be7d956a ]

max3100_shutdown() stops the polling timer but returns early during system suspend. If the SPI device is unbound before resume, the serial core does not call max3100_shutdown() again, so max3100_remove() frees the port while the timer remains armed. max3100_timeout() may then access the freed port and re-arm the timer.

Add final timer teardown to max3100_remove() and use timer_shutdown_sync() to prevent a racing callback from re-arming it. Also free the IRQ and destroy the workqueue there before freeing the port. Keep timer_delete_sync() in max3100_shutdown() so that a subsequent open() can re-arm the timer.

The workqueue is created before request_irq() and destroyed on both request_irq() failure and normal shutdown. Its presence at remove thus identifies the IRQ left registered when suspend bypasses shutdown.

Free the IRQ before destroying the workqueue, in both max3100_shutdown() and max3100_remove(), and cancel the pending work in between. free_irq() waits for a running interrupt handler to finish and no new handler can start afterwards, so a racing handler cannot queue work on a workqueue that is being destroyed; the force_end_work check in max3100_dowork() only narrows that window, as a handler delayed between the check and queue_work() could still run after the teardown has cleared the workqueue pointer. Cancelling the work also keeps destroy_workqueue() from waiting on a queued work item in case remove() ever runs while the freezable workqueue is still frozen, e.g. device removal during the resume window, before workqueues are thawed.

This issue was found by an in-house static analysis tool.

---
 drivers/tty/serial/max3100.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

index 67803242a70c2..4ba444460753c 100644
@@ -568,11 +568,11 @@ static void max3100_shutdown(struct uart_port *port)
 		del_timer_sync(&s->timer);
 
 	if (s->workqueue) {
+		free_irq(s->irq, s);
+		cancel_work_sync(&s->work);
 		destroy_workqueue(s->workqueue);
 		s->workqueue = NULL;
 	}
-	if (s->irq)
-		free_irq(s->irq, s);
 
 	/* set shutdown mode to save power */
 	if (s->max3100_hw_suspend)

@@ -831,6 +831,15 @@ static void max3100_remove(struct spi_device *spi)
 		if (max3100s[i] == s) {
 			dev_dbg(&spi->dev, "%s: removing port %d\n", __func__, i);
 			uart_remove_one_port(&max3100_uart_driver, &max3100s[i]->port);
+
+			s->force_end_work = 1;
+			timer_shutdown_sync(&s->timer);
+			if (s->workqueue) {
+				free_irq(s->irq, s);
+				cancel_work_sync(&s->work);
+				destroy_workqueue(s->workqueue);
+				s->workqueue = NULL;
+			}
 			kfree(max3100s[i]);
 			max3100s[i] = NULL;
 			break;

2.53.0