From 5a4234de5eb3f4608f4b4f42cb6da1a0e2c00c85 Mon Sep 17 00:00:00 2001 From: Michael Niedermayer Date: Sat, 15 Sep 2018 00:20:38 +0200 Subject: [PATCH] avcodec/mpeg4videodec: Fix undefined shift in get_amv() 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 (cherry picked from commit c88afa44c4823aba7b6f4a1b01fd6a4169643c57) Signed-off-by: Michael Niedermayer --- libavcodec/mpeg4videodec.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/libavcodec/mpeg4videodec.c b/libavcodec/mpeg4videodec.c index 1686ed1001..f9ec0fd0c9 100644 --- a/libavcodec/mpeg4videodec.c +++ b/libavcodec/mpeg4videodec.c @@ -596,7 +596,7 @@ 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);