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avcodec/msmpeg4dec: Skip frame if its smaller than 1/8 of the minimal size

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Frames that small are not valid and of limited use for error concealment, while
being very computationally intensive to process.

Fixes: Timeout
Fixes: 11318/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_MSMPEG4V1_fuzzer-5710884555456512

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
This commit is contained in:
Michael Niedermayer 2018-11-29 02:32:10 +01:00
parent ed5680f37e
commit 09ec182864
1 changed files with 8 additions and 0 deletions
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8
libavcodec/msmpeg4dec.c
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@ -412,6 +412,14 @@ int ff_msmpeg4_decode_picture_header(MpegEncContext * s)
{
int code;
// at minimum one bit per macroblock is required at least in a valid frame,
// we discard frames much smaller than this. Frames smaller than 1/8 of the
// smallest "black/skip" frame generally contain not much recoverable content
// while at the same time they have the highest computational requirements
// per byte
if (get_bits_left(&s->gb) * 8LL < (s->width+15)/16 * ((s->height+15)/16))
return AVERROR_INVALIDDATA;
if(s->msmpeg4_version==1){
int start_code = get_bits_long(&s->gb, 32);
if(start_code!=0x00000100){