linux-kernel - Re: [PATCH 8/8] platform: vivid-cec: fix potential integer overflow in vivid_cec_pin_adap

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Date:   Tue, 30 Jan 2018 08:21:54 +0100
From:   Hans Verkuil <hverkuil@...all.nl>
To:     "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>
Cc:     linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        "Gustavo A. R. Silva" <garsilva@...eddedor.com>
Subject: Re: [PATCH 8/8] platform: vivid-cec: fix potential integer overflow
 in vivid_cec_pin_adap_events

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@...eddedor.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.

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

Sorry,

	Hans

>  	cec_queue_pin_cec_event(adap, false, ts);
>  	ts = ktime_add_us(ts, CEC_TIM_START_BIT_LOW);
>  	cec_queue_pin_cec_event(adap, true, ts);
>