[FFmpeg-cvslog] avcodec/vb: Check for end of bytestream before reading blocktype

[Michael Niedermayer]

ffmpeg | branch: release/3.3 | Michael Niedermayer <michael at niedermayer.cc> | Mon Aug 20 22:19:23 2018 +0200| [347c50b0d4e7119e77edcd0871b5d9c841877af4] | committer: Michael Niedermayer

avcodec/vb: Check for end of bytestream before reading blocktype

Fixes: Timeout
Fixes: 9601/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_VB_fuzzer-4550228702134272

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 1cbac9ce20d32806febf64cbd9f830e1485695ca)
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=347c50b0d4e7119e77edcd0871b5d9c841877af4
---

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

diff --git a/libavcodec/vb.c b/libavcodec/vb.c
index 021657f7d8..c6dd6fb456 100644
--- a/libavcodec/vb.c
+++ b/libavcodec/vb.c
@@ -107,6 +107,10 @@ static int vb_decode_framedata(VBDecContext *c, int offset)
     blk2   = 0;
     for (blk = 0; blk < blocks; blk++) {
         if (!(blk & 3)) {
+            if (bytestream2_get_bytes_left(&g) < 1) {
+                av_log(c->avctx, AV_LOG_ERROR, "Insufficient data\n");
+                return AVERROR_INVALIDDATA;
+            }
             blocktypes = bytestream2_get_byte(&g);
         }
         switch (blocktypes & 0xC0) {