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 <mich...@niedermayer.cc> --- libavcodec/vc1_block.c | 4 ++-- 1 file 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 -- 2.23.0 _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
