[FFmpeg-cvslog] avcodec/h263dec: Check slice_ret in mspeg4 slice loop

[Michael Niedermayer]

ffmpeg | branch: release/3.3 | Michael Niedermayer <michael at niedermayer.cc> | Sun Apr 22 21:07:45 2018 +0200| [69f861be42ecb07e1deac86757760ec36a8e7bef] | committer: Michael Niedermayer

avcodec/h263dec: Check slice_ret in mspeg4 slice loop

Fixes infinite loop
Fixes: 6858/clusterfuzz-testcase-ffmpeg_AV_CODEC_ID_MSMPEG4V3_fuzzer-4681563766784000
Fixes: 6890/clusterfuzz-testcase-ffmpeg_AV_CODEC_ID_WMV1_fuzzer-4756103142309888

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 de841fbea7655b74a9663001e01008a86c88779a)
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=69f861be42ecb07e1deac86757760ec36a8e7bef
---

 libavcodec/h263dec.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libavcodec/h263dec.c b/libavcodec/h263dec.c
index 077666470d..8491db0ed6 100644
--- a/libavcodec/h263dec.c
+++ b/libavcodec/h263dec.c
@@ -637,7 +637,7 @@ retry:
     slice_ret = decode_slice(s);
     while (s->mb_y < s->mb_height) {
         if (s->msmpeg4_version) {
-            if (s->slice_height == 0 || s->mb_x != 0 ||
+            if (s->slice_height == 0 || s->mb_x != 0 || slice_ret < 0 ||
                 (s->mb_y % s->slice_height) != 0 || get_bits_left(&s->gb) < 0)
                 break;
         } else {