[PATCH] serial: 8250-dw: unregister 8250 port if clk_notifier_register() fails

[Stepan Ionichev <sozdayvek@gmail.com>]

dw8250_probe() registers the 8250 port via serial8250_register_8250_port()
and then, if the device has a clock, registers a clock notifier:

	data->data.line = serial8250_register_8250_port(up);
	if (data->data.line < 0)
		return data->data.line;
	...
	if (data->clk) {
		err = clk_notifier_register(data->clk, &data->clk_notifier);
		if (err)
			return dev_err_probe(dev, err,
					     "Failed to set the clock notifier\n");
		...
	}

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 in the serial8250 array 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 would be a use-after-free.

Unregister the port on the clk_notifier_register() error path.

Signed-off-by: Stepan Ionichev <sozdayvek@gmail.com>
---
 drivers/tty/serial/8250/8250_dw.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/serial/8250/8250_dw.c
index 94beadb40..7dbd79a91 100644
--- a/drivers/tty/serial/8250/8250_dw.c
+++ b/drivers/tty/serial/8250/8250_dw.c
@@ -850,8 +850,10 @@ 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);
 	}
 
-- 
2.43.0