[FFmpeg-cvslog] avcodec/bitstream: Check for integer code truncation in build_table()

[Michael Niedermayer]

ffmpeg | branch: release/4.1 | Michael Niedermayer <michael at niedermayer.cc> | Wed Jun  5 12:18:54 2019 +0200| [ec23fe0fd908e78b0bf23cf2b880dcb7a7c5640a] | committer: Michael Niedermayer

avcodec/bitstream: Check for integer code truncation in build_table()

Fixes: out of array read
Fixes: 14563/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_AGM_fuzzer-5646451545210880

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 e78b0f83748f92ea9e93b21c36082e0dd04d7cb1)
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=ec23fe0fd908e78b0bf23cf2b880dcb7a7c5640a
---

 libavcodec/bitstream.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/libavcodec/bitstream.c b/libavcodec/bitstream.c
index ed528fe4af..218412bb9b 100644
--- a/libavcodec/bitstream.c
+++ b/libavcodec/bitstream.c
@@ -226,6 +226,10 @@ static int build_table(VLC *vlc, int table_nb_bits, int nb_codes,
             /* note: realloc has been done, so reload tables */
             table = (volatile VLC_TYPE (*)[2])&vlc->table[table_index];
             table[j][0] = index; //code
+            if (table[j][0] != index) {
+                avpriv_request_sample(NULL, "strange codes");
+                return AVERROR_PATCHWELCOME;
+            }
             i = k-1;
         }
     }