[FFmpeg-cvslog] avcodec/snowdec: Check mv_scale

[Michael Niedermayer]

ffmpeg | branch: release/2.8 | Michael Niedermayer <michael at niedermayer.cc> | Fri Oct 13 03:06:54 2017 +0200| [c48262d85738587196e6dcc17a4e104cb0e362ac] | committer: Michael Niedermayer

avcodec/snowdec: Check mv_scale

Fixes: runtime error: signed integer overflow: 2 * -1094995530 cannot be represented in type 'int'
Fixes: 3512/clusterfuzz-testcase-minimized-4812747210489856

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 393d6fc7395611a38792e3c271b2be42ac45e672)
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=c48262d85738587196e6dcc17a4e104cb0e362ac
---

 libavcodec/snowdec.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/libavcodec/snowdec.c b/libavcodec/snowdec.c
index 526ea602bd..8c30a52813 100644
--- a/libavcodec/snowdec.c
+++ b/libavcodec/snowdec.c
@@ -391,9 +391,10 @@ static int decode_header(SnowContext *s){
     s->mv_scale       += get_symbol(&s->c, s->header_state, 1);
     s->qbias          += get_symbol(&s->c, s->header_state, 1);
     s->block_max_depth+= get_symbol(&s->c, s->header_state, 1);
-    if(s->block_max_depth > 1 || s->block_max_depth < 0){
+    if(s->block_max_depth > 1 || s->block_max_depth < 0 || s->mv_scale > 256U){
         av_log(s->avctx, AV_LOG_ERROR, "block_max_depth= %d is too large\n", s->block_max_depth);
         s->block_max_depth= 0;
+        s->mv_scale = 0;
         return AVERROR_INVALIDDATA;
     }
     if (FFABS(s->qbias) > 127) {