[FFmpeg-devel] [FFmpeg-cvslog] lavc/h264_levels: Avoid integer overflow in bitrate

[Mark Thompson]

On 26/09/18 22:43, Carl Eugen Hoyos wrote:
> 2018-09-25 0:16 GMT+02:00, Mark Thompson <git at videolan.org>:
>> ffmpeg | branch: master | Mark Thompson <sw at jkqxz.net> | Mon Sep 24 23:03:32
>> 2018 +0100| [581b4125aa187f2cf848d7a27e6128573c80dc64] | committer: Mark
>> Thompson
>>
>> lavc/h264_levels: Avoid integer overflow in bitrate
>>
>> Fixes CID #1439656.
>>
>>> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=581b4125aa187f2cf848d7a27e6128573c80dc64
>> ---
>>
>>  libavcodec/h264_levels.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/libavcodec/h264_levels.c b/libavcodec/h264_levels.c
>> index 6b4e18a914..737b7dcf06 100644
>> --- a/libavcodec/h264_levels.c
>> +++ b/libavcodec/h264_levels.c
>> @@ -105,7 +105,7 @@ const H264LevelDescriptor *ff_h264_guess_level(int
>> profile_idc,
>>          if (level->constraint_set3_flag && no_cs3f)
>>              continue;
>>
>> -        if (bitrate > level->max_br * h264_get_br_factor(profile_idc))
>> +        if (bitrate > (int64_t)level->max_br *
>> h264_get_br_factor(profile_idc))
> 
> If the overflow is possible at all (I doubt it), wouldn't it be cleaner
> to change the type of cpb_br_nal_factor to uint32_t?

Some of the largest cases overflow 32-bit signed int - e.g. level 6.2 in High 10 allows up to 800000 * 3600 = 2880000000 bps.  (High profile or lower doesn't have a cpbBrNalFactor large enough to hit this case.)

I used int64_t because that's the type of bitrate, on the other side of the comparison.

Thanks,

- Mark