This is a note to let you know that I've just added the patch titled
platform/x86: dell-uart-backlight: fix serdev race
to the 6.12-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
platform-x86-dell-uart-backlight-fix-serdev-race.patch
and it can be found in the queue-6.12 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 1f22e49e1424ddd96e75340f800cfc03e5cbeabb
Author: Chenyuan Yang <chenyuan0y@xxxxxxxxx>
Date: Sat Jan 11 12:01:18 2025 -0600
platform/x86: dell-uart-backlight: fix serdev race
[ Upstream commit 1b2128aa2d45ab20b22548dcf4b48906298ca7fd ]
The dell_uart_bl_serdev_probe() function calls devm_serdev_device_open()
before setting the client ops via serdev_device_set_client_ops(). This
ordering can trigger a NULL pointer dereference in the serdev controller's
receive_buf handler, as it assumes serdev->ops is valid when
SERPORT_ACTIVE is set.
This is similar to the issue fixed in commit 5e700b384ec1
("platform/chrome: cros_ec_uart: properly fix race condition") where
devm_serdev_device_open() was called before fully initializing the
device.
Fix the race by ensuring client ops are set before enabling the port via
devm_serdev_device_open().
Note, serdev_device_set_baudrate() and serdev_device_set_flow_control()
calls should be after the devm_serdev_device_open() call.
Fixes: 484bae9e4d6a ("platform/x86: Add new Dell UART backlight driver")
Signed-off-by: Chenyuan Yang <chenyuan0y@xxxxxxxxx>
Reviewed-by: Hans de Goede <hdegoede@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20250111180118.2274516-1-chenyuan0y@xxxxxxxxx
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/platform/x86/dell/dell-uart-backlight.c b/drivers/platform/x86/dell/dell-uart-backlight.c
index 3995f90add456..c45bc332af7a0 100644
--- a/drivers/platform/x86/dell/dell-uart-backlight.c
+++ b/drivers/platform/x86/dell/dell-uart-backlight.c
@@ -283,6 +283,9 @@ static int dell_uart_bl_serdev_probe(struct serdev_device *serdev)
init_waitqueue_head(&dell_bl->wait_queue);
dell_bl->dev = dev;
+ serdev_device_set_drvdata(serdev, dell_bl);
+ serdev_device_set_client_ops(serdev, &dell_uart_bl_serdev_ops);
+
ret = devm_serdev_device_open(dev, serdev);
if (ret)
return dev_err_probe(dev, ret, "opening UART device\n");
@@ -290,8 +293,6 @@ static int dell_uart_bl_serdev_probe(struct serdev_device *serdev)
/* 9600 bps, no flow control, these are the default but set them to be sure */
serdev_device_set_baudrate(serdev, 9600);
serdev_device_set_flow_control(serdev, false);
- serdev_device_set_drvdata(serdev, dell_bl);
- serdev_device_set_client_ops(serdev, &dell_uart_bl_serdev_ops);
get_version[0] = DELL_SOF(GET_CMD_LEN);
get_version[1] = CMD_GET_VERSION;
