[FFmpeg-cvslog] avformat/shortendec: Check k in probe

[Michael Niedermayer]

ffmpeg | branch: master | Michael Niedermayer <michael at niedermayer.cc> | Tue Sep 24 22:52:03 2019 +0200| [ea770eb55941a6ed7b86828d6ea2f4e718a4b337] | committer: Michael Niedermayer

avformat/shortendec: Check k in probe

Fixes: Assertion failure
Fixes: 17640/clusterfuzz-testcase-minimized-ffmpeg_DEMUXER_fuzzer-5708767475269632

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=ea770eb55941a6ed7b86828d6ea2f4e718a4b337
---

 libavformat/shortendec.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/libavformat/shortendec.c b/libavformat/shortendec.c
index a2879dc5a3..f7390b2e62 100644
--- a/libavformat/shortendec.c
+++ b/libavformat/shortendec.c
@@ -40,12 +40,18 @@ static int shn_probe(const AVProbeData *p)
         channels = get_ur_golomb_shorten(&gb, 0);
         blocksize = 256;
     } else {
-        int k;
+        unsigned k;
         k = get_ur_golomb_shorten(&gb, 2);
+        if (k > 31)
+            return 0;
         internal_ftype = get_ur_golomb_shorten(&gb, k);
         k = get_ur_golomb_shorten(&gb, 2);
+        if (k > 31)
+            return 0;
         channels = get_ur_golomb_shorten(&gb, k);
         k = get_ur_golomb_shorten(&gb, 2);
+        if (k > 31)
+            return 0;
         blocksize = get_ur_golomb_shorten(&gb, k);
     }