Re: [PATCH v4 4/4] media: venus: hfi: add a check to handle OOB in sfr region

[Vikash Garodia <quic_vgarodia@quicinc.com>]

On 2/20/2025 8:53 PM, Hans Verkuil wrote:
> On 2/7/25 09:24, Vikash Garodia wrote:
>> sfr->buf_size is in shared memory and can be modified by malicious user.
>> OOB write is possible when the size is made higher than actual sfr data
>> buffer. Cap the size to allocated size for such cases.
>>
>> Cc: stable@vger.kernel.org
>> Fixes: d96d3f30c0f2 ("[media] media: venus: hfi: add Venus HFI files")
>> Reviewed-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
>> Signed-off-by: Vikash Garodia <quic_vgarodia@quicinc.com>
>> ---
>>  drivers/media/platform/qcom/venus/hfi_venus.c | 9 +++++++--
>>  1 file changed, 7 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/media/platform/qcom/venus/hfi_venus.c b/drivers/media/platform/qcom/venus/hfi_venus.c
>> index 6b615270c5dae470c6fad408c9b5bc037883e56e..c3113420d266e61fcab44688580288d7408b50f4 100644
>> --- a/drivers/media/platform/qcom/venus/hfi_venus.c
>> +++ b/drivers/media/platform/qcom/venus/hfi_venus.c
>> @@ -1041,18 +1041,23 @@ static void venus_sfr_print(struct venus_hfi_device *hdev)
>>  {
>>  	struct device *dev = hdev->core->dev;
>>  	struct hfi_sfr *sfr = hdev->sfr.kva;
>> +	u32 size;
>>  	void *p;
>>  
>>  	if (!sfr)
>>  		return;
>>  
>> -	p = memchr(sfr->data, '\0', sfr->buf_size);
>> +	size = sfr->buf_size;
> 
> If this is ever 0...
> 
>> +	if (size > ALIGNED_SFR_SIZE)
>> +		size = ALIGNED_SFR_SIZE;
>> +
>> +	p = memchr(sfr->data, '\0', size);
>>  	/*
>>  	 * SFR isn't guaranteed to be NULL terminated since SYS_ERROR indicates
>>  	 * that Venus is in the process of crashing.
>>  	 */
>>  	if (!p)
>> -		sfr->data[sfr->buf_size - 1] = '\0';
>> +		sfr->data[size - 1] = '\0';
> 
> ...then this will overwrite memory. It probably can't be 0, but a check or perhaps
> just a comment might be good. It looks a bit scary.
Thats correct, it would not be 0 as its a prefixed one [1]. I can put up a
comment here.

[1]
https://elixir.bootlin.com/linux/v6.14-rc3/source/drivers/media/platform/qcom/venus/hfi_venus.c#L836
> 
> Regards,
> 
> 	Hans
> 
>>  
>>  	dev_err_ratelimited(dev, "SFR message from FW: %s\n", sfr->data);
>>  }
>>
Regards,
Vikash