avcodec/mpeg4videodec: Fix undefined shift in get_amv()
authorMichael Niedermayer <michael@niedermayer.cc>
Fri, 14 Sep 2018 22:20:38 +0000 (00:20 +0200)
committerMichael Niedermayer <michael@niedermayer.cc>
Wed, 19 Sep 2018 21:08:31 +0000 (23:08 +0200)
Fixes: runtime error: shift exponent -1 is negative
Fixes: 9938/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_MPEG4_fuzzer-5653783529914368

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
libavcodec/mpeg4videodec.c

index 853c6d9..f435a52 100644 (file)
@@ -598,7 +598,7 @@ static inline int get_amv(Mpeg4DecContext *ctx, int n)
         len >>= s->quarter_sample;
 
     if (s->real_sprite_warping_points == 1) {
-        if (ctx->divx_version == 500 && ctx->divx_build == 413)
+        if (ctx->divx_version == 500 && ctx->divx_build == 413 && a >= s->quarter_sample)
             sum = s->sprite_offset[0][n] / (1 << (a - s->quarter_sample));
         else
             sum = RSHIFT(s->sprite_offset[0][n] * (1 << s->quarter_sample), a);