[FFmpeg-devel] [PATCH] alsdec: validate time diff index

[Andreas Cadhalpun]

On 18.04.2015 20:42, Michael Niedermayer wrote:
> On Sat, Apr 18, 2015 at 08:13:30PM +0200, Andreas Cadhalpun wrote:
>> @@ -1290,8 +1290,16 @@ static int revert_channel_correlation(ALSDecContext *ctx, ALSBlockData *bd,
>>  
>>              if (ch[dep].time_diff_sign) {
>>                  t      = -t;
>> +                if (t > 0 && begin < t) {
> 
> time_diff_index is always positive, so t is always negative here

I didn't verify this, but I added the 'begin < t' check only for symmetry
with the end case.

> so this cant be true unless the context got corrupted or iam missing
> something

If you're sure t is always negative here, this check can be dropped.

>> +                    av_log(ctx->avctx, AV_LOG_ERROR, "begin %u smaller than time diff index %d.\n", begin, t);
>> +                    return AVERROR_INVALIDDATA;
>> +                }
>>                  begin -= t;
>>              } else {
>> +                if (t > 0 && end < t) {
> 
> and here t should always be > 0 so the test shouldnt be needed

I've only seen cases with t > 0, but the t > 0 check makes it explicit that
end < t is a comparison between unsigned variables. So I would leave it.

Best regards,
Andreas