[FFmpeg-cvslog] avcodec/tiff: Check geotag count for being non zero

[Michael Niedermayer]

ffmpeg | branch: master | Michael Niedermayer <michael at niedermayer.cc> | Tue Mar 21 01:55:01 2017 +0100| [3182e19c1c29eef60208a67ad8ecad1d9a2d0694] | committer: Michael Niedermayer

avcodec/tiff: Check geotag count for being non zero

Fixes memleak
Fixes: 874/clusterfuzz-testcase-5252796175613952

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/targets/ffmpeg
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=3182e19c1c29eef60208a67ad8ecad1d9a2d0694
---

 libavcodec/tiff.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/libavcodec/tiff.c b/libavcodec/tiff.c
index 5a6573f..3aaf633 100644
--- a/libavcodec/tiff.c
+++ b/libavcodec/tiff.c
@@ -1071,7 +1071,8 @@ static int tiff_decode_tag(TiffContext *s, AVFrame *frame)
             s->geotag_count = count / 4 - 1;
             av_log(s->avctx, AV_LOG_WARNING, "GeoTIFF key directory buffer shorter than specified\n");
         }
-        if (bytestream2_get_bytes_left(&s->gb) < s->geotag_count * sizeof(int16_t) * 4) {
+        if (   bytestream2_get_bytes_left(&s->gb) < s->geotag_count * sizeof(int16_t) * 4
+            || s->geotag_count == 0) {
             s->geotag_count = 0;
             return -1;
         }