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| author | Michael Niedermayer <michael@niedermayer.cc> | 2019-10-31 15:00:32 +0100 |
|---|---|---|
| committer | Michael Niedermayer <michael@niedermayer.cc> | 2020-01-06 11:30:44 +0100 |
| commit | 864649067b4b64494f283922fca861b1dc0a14fd (patch) | |
| tree | 366c6c8c3bcee6df55d441a89813fca3ef8c4545 | |
| parent | 65cda31ace22660c08444734661d1bb78d4629e9 (diff) | |
| download | ffmpeg-864649067b4b64494f283922fca861b1dc0a14fd.tar.gz | |
avcodec/vc1_block: Fix undefined behavior in ac prediction rescaling
The intermediates are required to fit in 12bit (8.1.3.9 Coefficient Scaling)
See SMPTE 421M-2006 and Amendment 1-2007
Fixes: signed integer overflow: -20691 * 262144 cannot be represented in type 'int'
Fixes: 18479/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_VC1_fuzzer-5128912371187712
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 7fc1baf0ca83ef06014878290339a59735603959)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
| -rw-r--r-- | libavcodec/vc1_block.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/libavcodec/vc1_block.c b/libavcodec/vc1_block.c index 4c6dfaf6bf..da0eee8cc7 100644 --- a/libavcodec/vc1_block.c +++ b/libavcodec/vc1_block.c @@ -1036,10 +1036,10 @@ static int vc1_decode_intra_block(VC1Context *v, int16_t block[64], int n, if (q2 && q1 != q2) { if (dc_pred_dir) { // left for (k = 1; k < 8; k++) - block[k << v->left_blk_sh] += (ac_val[k] * q2 * ff_vc1_dqscale[q1 - 1] + 0x20000) >> 18; + block[k << v->left_blk_sh] += (int)(ac_val[k] * q2 * (unsigned)ff_vc1_dqscale[q1 - 1] + 0x20000) >> 18; } else { //top for (k = 1; k < 8; k++) - block[k << v->top_blk_sh] += (ac_val[k + 8] * q2 * ff_vc1_dqscale[q1 - 1] + 0x20000) >> 18; + block[k << v->top_blk_sh] += (int)(ac_val[k + 8] * q2 * (unsigned)ff_vc1_dqscale[q1 - 1] + 0x20000) >> 18; } } else { if (dc_pred_dir) { // left |