[FFmpeg-cvslog] avcodec/webp: Fix signedness in prefix_code check

[Michael Niedermayer]

ffmpeg | branch: master | Michael Niedermayer <michael at niedermayer.cc> | Sat May 13 23:21:24 2017 +0200| [8c5cd1c9d33b4b287f85d42efb1aecfaee31de6c] | committer: Michael Niedermayer

avcodec/webp: Fix signedness in prefix_code check

Fixes: out of array read
Fixes: 1557/clusterfuzz-testcase-minimized-6535013757616128

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

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=8c5cd1c9d33b4b287f85d42efb1aecfaee31de6c
---

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

diff --git a/libavcodec/webp.c b/libavcodec/webp.c
index 8281cc45b4..50a8da1000 100644
--- a/libavcodec/webp.c
+++ b/libavcodec/webp.c
@@ -694,7 +694,7 @@ static int decode_entropy_coded_image(WebPContext *s, enum ImageRole role,
                 length = offset + get_bits(&s->gb, extra_bits) + 1;
             }
             prefix_code = huff_reader_get_symbol(&hg[HUFF_IDX_DIST], &s->gb);
-            if (prefix_code > 39) {
+            if (prefix_code > 39U) {
                 av_log(s->avctx, AV_LOG_ERROR,
                        "distance prefix code too large: %d\n", prefix_code);
                 return AVERROR_INVALIDDATA;