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avcodec/mpeg12dec: Do not put mpeg_f_code into an invalid state on error return 

Fixes: invalid shift
Fixes: 37018/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_MPEG2VIDEO_fuzzer-5290280902328320

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
(cherry picked from commit 5a95abcce4)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
This commit is contained in:
Michael Niedermayer 2021-08-31 20:15:09 +02:00
parent 10226f869e
commit 6edcacf465
1 changed files with 4 additions and 4 deletions
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8
libavcodec/mpeg12dec.c
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@ -1537,6 +1537,10 @@ static void mpeg_decode_picture_coding_extension(Mpeg1Context *s1)
s->mpeg_f_code[0][1] = get_bits(&s->gb, 4);
s->mpeg_f_code[1][0] = get_bits(&s->gb, 4);
s->mpeg_f_code[1][1] = get_bits(&s->gb, 4);
s->mpeg_f_code[0][0] += !s->mpeg_f_code[0][0];
s->mpeg_f_code[0][1] += !s->mpeg_f_code[0][1];
s->mpeg_f_code[1][0] += !s->mpeg_f_code[1][0];
s->mpeg_f_code[1][1] += !s->mpeg_f_code[1][1];
if (!s->pict_type && s1->mpeg_enc_ctx_allocated) {
av_log(s->avctx, AV_LOG_ERROR,
"Missing picture start code, guessing missing values\n");
@ -1550,10 +1554,6 @@ static void mpeg_decode_picture_coding_extension(Mpeg1Context *s1)
s->current_picture.f->pict_type = s->pict_type;
s->current_picture.f->key_frame = s->pict_type == AV_PICTURE_TYPE_I;
}
s->mpeg_f_code[0][0] += !s->mpeg_f_code[0][0];
s->mpeg_f_code[0][1] += !s->mpeg_f_code[0][1];
s->mpeg_f_code[1][0] += !s->mpeg_f_code[1][0];
s->mpeg_f_code[1][1] += !s->mpeg_f_code[1][1];
s->intra_dc_precision = get_bits(&s->gb, 2);
s->picture_structure = get_bits(&s->gb, 2);