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avcodec/mpc8: Fixes invalid shift in mpc8_decode_frame()

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Fixes: left shift of negative value -456
Fixes: 15561/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_MPC8_fuzzer-5758130404720640

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Suggested-by: James Almer <jamrial@gmail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
(cherry picked from commit 1dbb67d39b)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
This commit is contained in:
Michael Niedermayer 2019-07-11 20:02:24 +02:00
parent cea8e10a0f
commit 71100d7102
1 changed files with 3 additions and 2 deletions
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5
libavcodec/mpc8.c
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@ -362,8 +362,9 @@ static int mpc8_decode_frame(AVCodecContext * avctx, void *data,
for(j = 0; j < SAMPLES_PER_BAND; j += SAMPLES_PER_BAND / 2){
cnt = get_vlc2(gb, q1_vlc.table, MPC8_Q1_BITS, 2);
t = mpc8_get_mask(gb, 18, cnt);
for(k = 0; k < SAMPLES_PER_BAND / 2; k++, t <<= 1)
c->Q[ch][off + j + k] = (t & 0x20000) ? (get_bits1(gb) << 1) - 1 : 0;
for(k = 0; k < SAMPLES_PER_BAND / 2; k++)
c->Q[ch][off + j + k] = t & (1 << (SAMPLES_PER_BAND / 2 - k - 1))
? (get_bits1(gb) << 1) - 1 : 0;
}
break;
case 2: