[FFmpeg-cvslog] avcodec/snowdec: Sanity check hcoeff

[Michael Niedermayer]

ffmpeg | branch: master | Michael Niedermayer <michael at niedermayer.cc> | Thu Aug  6 21:35:06 2020 +0200| [d51d569cf68f78aaea8464a156c847a0e294726a] | committer: Michael Niedermayer

avcodec/snowdec: Sanity check hcoeff

Fixes: signed integer overflow: -2147483648 * -1 cannot be represented in type 'int'
Fixes: 24011/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_SNOW_fuzzer-5486376610168832

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=d51d569cf68f78aaea8464a156c847a0e294726a
---

 libavcodec/snowdec.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/libavcodec/snowdec.c b/libavcodec/snowdec.c
index 88664dc472..5e69f39022 100644
--- a/libavcodec/snowdec.c
+++ b/libavcodec/snowdec.c
@@ -369,7 +369,10 @@ static int decode_header(SnowContext *s){
                 htaps = htaps*2 + 2;
                 p->htaps= htaps;
                 for(i= htaps/2; i; i--){
-                    p->hcoeff[i]= get_symbol(&s->c, s->header_state, 0) * (1-2*(i&1));
+                    unsigned hcoeff = get_symbol(&s->c, s->header_state, 0);
+                    if (hcoeff > 127)
+                        return AVERROR_INVALIDDATA;
+                    p->hcoeff[i]= hcoeff * (1-2*(i&1));
                     sum += p->hcoeff[i];
                 }
                 p->hcoeff[0]= 32-sum;