linux-kernel - Re: [PATCH] w1: fix NULL pointer dereference in probe

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Message-ID: <Z4upeb9_AvUpE6xS@cjw-notebook>
Date: Sat, 18 Jan 2025 14:15:37 +0100
From: Christoph Winklhofer <cj.winklhofer@...il.com>
To: Chenyuan Yang <chenyuan0y@...il.com>
Cc: krzk@...nel.org, linux-kernel@...r.kernel.org, zijie98@...il.com
Subject: Re: [PATCH] w1: fix NULL pointer dereference in probe

On Sat, Jan 11, 2025 at 12:18:03PM -0600, Chenyuan Yang wrote:
> The w1_uart_probe() function calls w1_uart_serdev_open() (which includes
> 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
> w1_uart_serdev_open().
> 
> Fixes: a3c08804364e ("w1: add UART w1 bus driver")
> Signed-off-by: Chenyuan Yang <chenyuan0y@...il.com>
> ---
>  drivers/w1/masters/w1-uart.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 

Acked-by: Christoph Winklhofer <cj.winklhofer@...il.com>

Thanks for the fix!
I tested it with a Raspberry PI and DS18B20 sensor.

Best,
Christoph