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platform/x86: dell-uart-backlight: fix serdev race

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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 5e700b384e
("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: 484bae9e4d ("platform/x86: Add new Dell UART backlight driver")
Signed-off-by: Chenyuan Yang <chenyuan0y@gmail.com>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/20250111180118.2274516-1-chenyuan0y@gmail.com
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
This commit is contained in:
Chenyuan Yang 2025-01-11 12:01:18 -06:00 committed by Ilpo Järvinen
parent 1d7461d0c8
commit 1b2128aa2d
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GPG Key ID: 59AC4F6153E5CE31
1 changed files with 3 additions and 2 deletions
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5
drivers/platform/x86/dell/dell-uart-backlight.c
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@ -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;