[FFmpeg-cvslog] avcodec/snowdec: Fix integer overflow in header parsing

[Michael Niedermayer]

ffmpeg | branch: release/3.3 | Michael Niedermayer <michael at niedermayer.cc> | Sun Nov  5 21:20:05 2017 +0100| [c8027878d024394fc59184ffdf7182fae0bf38dd] | committer: Michael Niedermayer

avcodec/snowdec: Fix integer overflow in header parsing

Fixes: 3984/clusterfuzz-testcase-minimized-5265759929368576
Fixes: runtime error: signed integer overflow: -1085585801 + -1094995529 cannot be represented in type 'int'

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 c897a9285846b6a072b9650976afd4f091b7a71f)
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=c8027878d024394fc59184ffdf7182fae0bf38dd
---

 libavcodec/snowdec.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/libavcodec/snowdec.c b/libavcodec/snowdec.c
index 6eff729a19..2b92ed3de0 100644
--- a/libavcodec/snowdec.c
+++ b/libavcodec/snowdec.c
@@ -374,7 +374,7 @@ static int decode_header(SnowContext *s){
         }
     }
 
-    s->spatial_decomposition_type+= get_symbol(&s->c, s->header_state, 1);
+    s->spatial_decomposition_type+= (unsigned)get_symbol(&s->c, s->header_state, 1);
     if(s->spatial_decomposition_type > 1U){
         av_log(s->avctx, AV_LOG_ERROR, "spatial_decomposition_type %d not supported\n", s->spatial_decomposition_type);
         return AVERROR_INVALIDDATA;
@@ -390,10 +390,10 @@ static int decode_header(SnowContext *s){
     }
 
 
-    s->qlog           += get_symbol(&s->c, s->header_state, 1);
-    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);
+    s->qlog           += (unsigned)get_symbol(&s->c, s->header_state, 1);
+    s->mv_scale       += (unsigned)get_symbol(&s->c, s->header_state, 1);
+    s->qbias          += (unsigned)get_symbol(&s->c, s->header_state, 1);
+    s->block_max_depth+= (unsigned)get_symbol(&s->c, s->header_state, 1);
     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;