[FFmpeg-cvslog] avcodec/shorten: Check non COMM chunk len before skip in decode_aiff_header()

[Michael Niedermayer]

ffmpeg | branch: release/4.0 | Michael Niedermayer <michael at niedermayer.cc> | Tue Jun  5 02:33:43 2018 +0200| [7a5ddf731b5cc68bb199ccc7c826de04f7f83bf9] | committer: Michael Niedermayer

avcodec/shorten: Check non COMM chunk len before skip in decode_aiff_header()

Fixes: signed integer overflow: 2147483647 + 1 cannot be represented in type 'int'
Fixes: 8024/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_SHORTEN_fuzzer-5109204648984576

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 424a81df107b63a166894a4aee3d27702ae3f459)
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=7a5ddf731b5cc68bb199ccc7c826de04f7f83bf9
---

 libavcodec/shorten.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/libavcodec/shorten.c b/libavcodec/shorten.c
index 49af6beec6..ae0cdfe09d 100644
--- a/libavcodec/shorten.c
+++ b/libavcodec/shorten.c
@@ -234,11 +234,11 @@ static int decode_aiff_header(AVCodecContext *avctx, const uint8_t *header,
 
     while (bytestream2_get_le32(&gb) != MKTAG('C', 'O', 'M', 'M')) {
         len = bytestream2_get_be32(&gb);
-        bytestream2_skip(&gb, len + (len & 1));
-        if (len < 0 || bytestream2_get_bytes_left(&gb) < 18) {
+        if (len < 0 || bytestream2_get_bytes_left(&gb) < 18LL + len + (len&1)) {
             av_log(avctx, AV_LOG_ERROR, "no COMM chunk found\n");
             return AVERROR_INVALIDDATA;
         }
+        bytestream2_skip(&gb, len + (len & 1));
     }
     len = bytestream2_get_be32(&gb);