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avcodec/vc1_block: Fix integer overflow in ff_vc1_pred_dc()

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Fixes: signed integer overflow: 32796 * 65536 cannot be represented in type 'int'
Fixes: 15430/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_VC1IMAGE_fuzzer-5735424087031808

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 f31ed8f3b00ec7afe87092798bf0b397f6e19ed5)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
This commit is contained in:
Michael Niedermayer 2019-07-04 23:13:13 +02:00
parent e6701fa94b
commit 5c1a6ecb98
1 changed files with 3 additions and 3 deletions
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6
libavcodec/vc1_block.c
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@ -411,12 +411,12 @@ static inline int ff_vc1_pred_dc(MpegEncContext *s, int overlap, int pq, int n,
if (c_avail && (n != 1 && n != 3)) {
q2 = s->current_picture.qscale_table[mb_pos - 1];
if (q2 && q2 != q1)
c = (c * s->y_dc_scale_table[q2] * ff_vc1_dqscale[dqscale_index] + 0x20000) >> 18;
c = (int)((unsigned)c * s->y_dc_scale_table[q2] * ff_vc1_dqscale[dqscale_index] + 0x20000) >> 18;
}
if (a_avail && (n != 2 && n != 3)) {
q2 = s->current_picture.qscale_table[mb_pos - s->mb_stride];
if (q2 && q2 != q1)
a = (a * s->y_dc_scale_table[q2] * ff_vc1_dqscale[dqscale_index] + 0x20000) >> 18;
a = (int)((unsigned)a * s->y_dc_scale_table[q2] * ff_vc1_dqscale[dqscale_index] + 0x20000) >> 18;
}
if (a_avail && c_avail && (n != 3)) {
int off = mb_pos;
@ -426,7 +426,7 @@ static inline int ff_vc1_pred_dc(MpegEncContext *s, int overlap, int pq, int n,
off -= s->mb_stride;
q2 = s->current_picture.qscale_table[off];
if (q2 && q2 != q1)
b = (b * s->y_dc_scale_table[q2] * ff_vc1_dqscale[dqscale_index] + 0x20000) >> 18;
b = (int)((unsigned)b * s->y_dc_scale_table[q2] * ff_vc1_dqscale[dqscale_index] + 0x20000) >> 18;
}
if (c_avail && (!a_avail || abs(a - b) <= abs(b - c))) {