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SubjectRe: [PATCH 8/8] platform: vivid-cec: fix potential integer overflow in vivid_cec_pin_adap_events
Hi Hans,

Quoting Hans Verkuil <hverkuil@xs4all.nl>:

> Hi Gustavo,
>
> On 01/30/2018 01:33 AM, Gustavo A. R. Silva wrote:
>> Cast len to const u64 in order to avoid a potential integer
>> overflow. This variable is being used in a context that expects
>> an expression of type const u64.
>>
>> Addresses-Coverity-ID: 1454996 ("Unintentional integer overflow")
>> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
>> ---
>> drivers/media/platform/vivid/vivid-cec.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/media/platform/vivid/vivid-cec.c
>> b/drivers/media/platform/vivid/vivid-cec.c
>> index b55d278..30240ab 100644
>> --- a/drivers/media/platform/vivid/vivid-cec.c
>> +++ b/drivers/media/platform/vivid/vivid-cec.c
>> @@ -83,7 +83,7 @@ static void vivid_cec_pin_adap_events(struct
>> cec_adapter *adap, ktime_t ts,
>> if (adap == NULL)
>> return;
>> ts = ktime_sub_us(ts, (CEC_TIM_START_BIT_TOTAL +
>> - len * 10 * CEC_TIM_DATA_BIT_TOTAL));
>> + (const u64)len * 10 * CEC_TIM_DATA_BIT_TOTAL));
>
> This makes no sense. Certainly the const part is pointless. And given that
> len is always <= 16 there definitely is no overflow.
>

Yeah, I understand your point and I know there is no chance of an
overflow in this particular case.

> I don't really want this cast in the code.
>
> Sorry,
>

I'm working through all the Linux kernel Coverity reports, and I
thought of sending a patch for this because IMHO it doesn't hurt to
give the compiler complete information about the arithmetic in which
an expression is intended to be evaluated.

I agree that the _const_ part is a bit odd. What do you think about
the cast to u64 alone?

I appreciate your feedback.

Thanks
--
Gustavo





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