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

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Message-ID: <7up54twtzt2ljricy6pf4xfggi5ztcuspr3tysb43rqreminrc@tjqmujuglhnl>
Date: Thu, 17 Jul 2025 00:17:59 +0200
From: Andi Shyti <andi.shyti@...nel.org>
To: forbidden405@...look.com
Cc: Stephan Gerhold <stephan.gerhold@...nkonzept.com>, 
	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 Mon, Jun 16, 2025 at 12:01:10AM +0800, 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>

I think you also need:

Fixes: fbfab1ab0658 ("i2c: qup: reorganization of driver code to remove polling for qup v1")

> ---
>  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;
> +		}

Well spotted Yang! I think this was the original idea, as well.
Merged to i2c/i2c-host-fixes.

Andi

>  
>  		usleep_range(len, len * 2);
>  	}
> 
> ---
> base-commit: 19272b37aa4f83ca52bdf9c16d5d81bdd1354494
> change-id: 20250615-qca-i2c-d41bb61aa59e
> 
> Best regards,
> -- 
> Yang Xiwen <forbidden405@...look.com>
> 
>