[PATCH] i2c: qup: jump out of the loop in case of timeout

[PATCH] i2c: qup: jump out of the loop in case of timeout

[Yang Xiwen via B4 Relay]

From: Yang Xiwen <forbidden405@outlook.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@vger.kernel.org
Signed-off-by: Yang Xiwen <forbidden405@outlook.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,
-- 
Yang Xiwen <forbidden405@outlook.com>

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

[Yang Xiwen]

On 6/16/2025 12:01 AM, Yang Xiwen via B4 Relay wrote:
> From: Yang Xiwen <forbidden405@outlook.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@vger.kernel.org
> Signed-off-by: Yang Xiwen <forbidden405@outlook.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

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

[Konrad Dybcio]

On 28-Jun-25 17:58, Yang Xiwen wrote:
> On 6/16/2025 12:01 AM, Yang Xiwen via B4 Relay wrote:
>> From: Yang Xiwen <forbidden405@outlook.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@vger.kernel.org
>> Signed-off-by: Yang Xiwen <forbidden405@outlook.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.

'return -ETIMEDOUT' makes sense here, AFAICT

Konrad

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

[Andi Shyti]

On Mon, Jun 16, 2025 at 12:01:10AM +0800, Yang Xiwen via B4 Relay wrote:
> From: Yang Xiwen <forbidden405@outlook.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@vger.kernel.org
> Signed-off-by: Yang Xiwen <forbidden405@outlook.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@outlook.com>
> 
>