linux-kernel - Re: [PATCH] i2c: qup: jump out of the loop in case of timeout

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Message-ID:
 <SEYPR02MB55575E3DE3A107D36F5393AD9644A@SEYPR02MB5557.apcprd02.prod.outlook.com>
Date: Sat, 28 Jun 2025 23:58:03 +0800
From: Yang Xiwen <forbidden405@...look.com>
To: Andi Shyti <andi.shyti@...nel.org>,
 Stephan Gerhold <stephan.gerhold@...nkonzept.com>
Cc: linux-arm-msm@...r.kernel.org, linux-i2c@...r.kernel.org,
 linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH] i2c: qup: jump out of the loop in case of timeout

On 6/16/2025 12:01 AM, Yang Xiwen via B4 Relay wrote:
> From: Yang Xiwen <forbidden405@...look.com>
>
> Original logic only sets the return value but doesn't jump out of the
> loop if the bus is kept active by a client. This is not expected. A
> malicious or buggy i2c client can hang the kernel in this case and
> should be avoided. This is observed during a long time test with a
> PCA953x GPIO extender.
>
> Fix it by changing the logic to not only sets the return value, but also
> jumps out of the loop and return to the caller with -ETIMEDOUT.
>
> Cc: stable@...r.kernel.org
> Signed-off-by: Yang Xiwen <forbidden405@...look.com>
> ---
>   drivers/i2c/busses/i2c-qup.c | 4 +++-
>   1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/i2c/busses/i2c-qup.c b/drivers/i2c/busses/i2c-qup.c
> index 3a36d682ed57..5b053e51f4c9 100644
> --- a/drivers/i2c/busses/i2c-qup.c
> +++ b/drivers/i2c/busses/i2c-qup.c
> @@ -452,8 +452,10 @@ static int qup_i2c_bus_active(struct qup_i2c_dev *qup, int len)
>   		if (!(status & I2C_STATUS_BUS_ACTIVE))
>   			break;
>   
> -		if (time_after(jiffies, timeout))
> +		if (time_after(jiffies, timeout)) {
>   			ret = -ETIMEDOUT;
> +			break;
> +		}
>   
>   		usleep_range(len, len * 2);
>   	}
>
> ---
> base-commit: 19272b37aa4f83ca52bdf9c16d5d81bdd1354494
> change-id: 20250615-qca-i2c-d41bb61aa59e
>
> Best regards,

Ping for review. The original logic error is very clear. This patch is 
also very small and can be reviewed in a short time.

If it insists on waiting for the bit to clear, it should not return 
-ETIMEDOUT then.

-- 
Regards,
Yang Xiwen