[FFmpeg-cvslog] avcodec/h265_metadata_bsf: Check nb_units before accessing the first in h265_metadata_update_fragment()

[Michael Niedermayer]

ffmpeg | branch: release/4.4 | Michael Niedermayer <michael at niedermayer.cc> | Tue Mar 30 12:36:08 2021 +0200| [de9f4351fa7db3e652767adf6ada17273fffbe6d] | committer: Michael Niedermayer

avcodec/h265_metadata_bsf: Check nb_units before accessing the first in h265_metadata_update_fragment()

Fixes: null pointer dereference
Fixes: 32113/clusterfuzz-testcase-minimized-ffmpeg_BSF_HEVC_METADATA_fuzzer-4803262287052800

Same as 0c48c332eeb2866d9353125f701e099c48889463

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 497ea04dbda78d4eb9cffd208737b676f838725c)
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=de9f4351fa7db3e652767adf6ada17273fffbe6d
---

 libavcodec/h265_metadata_bsf.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libavcodec/h265_metadata_bsf.c b/libavcodec/h265_metadata_bsf.c
index 59325c0471..d841839762 100644
--- a/libavcodec/h265_metadata_bsf.c
+++ b/libavcodec/h265_metadata_bsf.c
@@ -335,7 +335,7 @@ static int h265_metadata_update_fragment(AVBSFContext *bsf, AVPacket *pkt,
     int err, i;
 
     // If an AUD is present, it must be the first NAL unit.
-    if (au->units[0].type == HEVC_NAL_AUD) {
+    if (au->nb_units && au->units[0].type == HEVC_NAL_AUD) {
         if (ctx->aud == BSF_ELEMENT_REMOVE)
             ff_cbs_delete_unit(au, 0);
     } else {