FAILED: patch "[PATCH] serial: 8250_dw: unregister 8250 port if" failed to apply to 6.6-stable tree

The patch below does not apply to the 6.6-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-6.6.y
git checkout FETCH_HEAD
git cherry-pick -x 10fc708b4de7f86002d2d735a2dbf3b5b7f65692
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026062538-lash-atrium-5f0f@gregkh' --subject-prefix 'PATCH 6.6.y' 'HEAD^..'

Possible dependencies:

thanks,

greg k-h

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

From 10fc708b4de7f86002d2d735a2dbf3b5b7f65692 Mon Sep 17 00:00:00 2001
From: Stepan Ionichev <[email protected]>
Date: Thu, 14 May 2026 19:37:45 +0500
Subject: [PATCH] serial: 8250_dw: unregister 8250 port if
clk_notifier_register() fails

dw8250_probe() registers the 8250 port via serial8250_register_8250_port() and then, if the device has a clock, registers a clock notifier. If clk_notifier_register() fails, probe returns the error but leaves the 8250 port registered. The matching serial8250_unregister_port() lives in dw8250_remove(), which is not called when probe fails, so the port slot stays occupied until the device is rebound or the system is rebooted. The devm-allocated driver data is freed while the port still references it (via the saved private_data and serial_in/serial_out callbacks), so any access to that port slot before a rebind is a use-after-free hazard.

Unregister the port on the clk_notifier_register() error path.

index 55e40c10f46a..2d30a164eeae 100644
@@ -839,8 +839,10 @@ static int dw8250_probe(struct platform_device *pdev)
 	 */
 	if (data->clk) {
 		err = clk_notifier_register(data->clk, &data->clk_notifier);
-		if (err)
+		if (err) {
+			serial8250_unregister_port(data->data.line);
 			return dev_err_probe(dev, err, "Failed to set the clock notifier\n");
+		}
 		queue_work(system_dfl_wq, &data->clk_work);
 	}
 

From: Stepan Ionichev <[email protected]>

[ Upstream commit 10fc708b4de7f86002d2d735a2dbf3b5b7f65692 ]

dw8250_probe() registers the 8250 port via serial8250_register_8250_port() and then, if the device has a clock, registers a clock notifier. If clk_notifier_register() fails, probe returns the error but leaves the 8250 port registered. The matching serial8250_unregister_port() lives in dw8250_remove(), which is not called when probe fails, so the port slot stays occupied until the device is rebound or the system is rebooted. The devm-allocated driver data is freed while the port still references it (via the saved private_data and serial_in/serial_out callbacks), so any access to that port slot before a rebind is a use-after-free hazard.

Unregister the port on the clk_notifier_register() error path.

---
 drivers/tty/serial/8250/8250_dw.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

index 60a05bfecde39c..d1cf00cd945d97 100644
@@ -688,8 +688,10 @@ static int dw8250_probe(struct platform_device *pdev)
 	 */
 	if (data->clk) {
 		err = clk_notifier_register(data->clk, &data->clk_notifier);
-		if (err)
+		if (err) {
+			serial8250_unregister_port(data->data.line);
 			return dev_err_probe(dev, err, "Failed to set the clock notifier\n");
+		}
 		queue_work(system_unbound_wq, &data->clk_work);
 	}
 

2.53.0