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avcodec/mpeg4videodec: Check idx in mpeg4_decode_studio_block()

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Fixes: Out of array access
Fixes: 13500/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_MPEG4_fuzzer-5769760178962432

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Reviewed-by: Kieran Kunhya <kierank@obe.tv>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
This commit is contained in:
Michael Niedermayer 2019-03-10 01:40:59 +01:00
parent 3f086a2f66
commit d227ed5d59
1 changed files with 6 additions and 0 deletions
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6
libavcodec/mpeg4videodec.c
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@ -1899,14 +1899,20 @@ static int mpeg4_decode_studio_block(MpegEncContext *s, int32_t block[64], int n
code >>= 1;
run = (1 << (additional_code_len - 1)) + code;
idx += run;
if (idx > 63)
return AVERROR_INVALIDDATA;
j = scantable[idx++];
block[j] = sign ? 1 : -1;
} else if (group >= 13 && group <= 20) {
/* Level value (Table B.49) */
if (idx > 63)
return AVERROR_INVALIDDATA;
j = scantable[idx++];
block[j] = get_xbits(&s->gb, additional_code_len);
} else if (group == 21) {
/* Escape */
if (idx > 63)
return AVERROR_INVALIDDATA;
j = scantable[idx++];
additional_code_len = s->avctx->bits_per_raw_sample + s->dct_precision + 4;
flc = get_bits(&s->gb, additional_code_len);