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avcodec/wmv2dec: skip frames that have only skiped MBs

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This requires us to pre-parse the skip data, as we want to
detect this before allocating all the arrays

Fixes: Timeout
Fixes: 9708/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_WMV2_fuzzer-5729709861109760

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 2018-08-26 15:57:54 +02:00
parent 93a203662f
commit 0c88a5d3eb
1 changed files with 15 additions and 0 deletions
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15
libavcodec/wmv2dec.c
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@ -141,6 +141,21 @@ int ff_wmv2_decode_picture_header(MpegEncContext *s)
if (s->qscale <= 0)
return AVERROR_INVALIDDATA;
if (s->pict_type != AV_PICTURE_TYPE_I && show_bits(&s->gb, 1)) {
GetBitContext gb = s->gb;
int skip_type = get_bits(&gb, 2);
int run = skip_type == SKIP_TYPE_COL ? s->mb_width : s->mb_height;
while (run > 0) {
int block = FFMIN(run, 25);
if (get_bits(&gb, block) + 1 != 1<<block)
break;
run -= block;
}
if (!run)
return FRAME_SKIPPED;
}
return 0;
}