[FFmpeg-cvslog] avcodec/vc1_block: Check for double escapes

[Michael Niedermayer]

ffmpeg | branch: master | Michael Niedermayer <michael at niedermayer.cc> | Thu Aug 15 18:47:54 2019 +0200| [6962fd586e1a9a98828866dcfb4114af30c8c756] | committer: Michael Niedermayer

avcodec/vc1_block: Check for double escapes

Fixes: out of array read
Fixes: 16331/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_WMV3IMAGE_fuzzer-5672735195267072

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

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=6962fd586e1a9a98828866dcfb4114af30c8c756
---

 libavcodec/vc1_block.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libavcodec/vc1_block.c b/libavcodec/vc1_block.c
index 94184b0873..775e3c516b 100644
--- a/libavcodec/vc1_block.c
+++ b/libavcodec/vc1_block.c
@@ -526,7 +526,7 @@ static int vc1_decode_ac_coeff(VC1Context *v, int *last, int *skip,
         int escape = decode210(gb);
         if (escape != 2) {
             index = get_vlc2(gb, ff_vc1_ac_coeff_table[codingset].table, AC_VLC_BITS, 3);
-            if (index < 0)
+            if (index >= ff_vc1_ac_sizes[codingset] - 1U)
                 return AVERROR_INVALIDDATA;
             run   = vc1_index_decode_table[codingset][index][0];
             level = vc1_index_decode_table[codingset][index][1];