[FFmpeg-cvslog] avcodec/snowdec: Fix off by 1 error

[Michael Niedermayer]

ffmpeg | branch: release/3.1 | Michael Niedermayer <michael at niedermayer.cc> | Thu Aug 17 20:32:03 2017 +0200| [1b5548cc0913032587b4579e4b8b23ebed4c5124] | committer: Michael Niedermayer

avcodec/snowdec: Fix off by 1 error

Fixes: runtime error: index 4 out of bounds for type 'int8_t [4]'
Fixes: 3023/clusterfuzz-testcase-minimized-6421736130084864

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
(cherry picked from commit d132683ddd4050d3fe103ca88c73258c3442dc34)
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=1b5548cc0913032587b4579e4b8b23ebed4c5124
---

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

diff --git a/libavcodec/snowdec.c b/libavcodec/snowdec.c
index 7d6d7ff44f..4ebfa07c6a 100644
--- a/libavcodec/snowdec.c
+++ b/libavcodec/snowdec.c
@@ -355,7 +355,7 @@ static int decode_header(SnowContext *s){
                 Plane *p= &s->plane[plane_index];
                 p->diag_mc= get_rac(&s->c, s->header_state);
                 htaps= get_symbol(&s->c, s->header_state, 0)*2 + 2;
-                if((unsigned)htaps > HTAPS_MAX || htaps==0)
+                if((unsigned)htaps >= HTAPS_MAX || htaps==0)
                     return AVERROR_INVALIDDATA;
                 p->htaps= htaps;
                 for(i= htaps/2; i; i--){