This is an automated email from the git hooks/post-receive script.
Git pushed a commit to branch master
in repository ffmpeg.
The following commit(s) were added to refs/heads/master by this push:
new 9f35e220ff avformat/movenc: fix crash when flushing a fragment with no
data
9f35e220ff is described below
commit 9f35e220ffbba21c88356eb2bbfa3679ede93793
Author: Ackanir <[email protected]>
AuthorDate: Mon Aug 17 14:36:53 2026 +0200
Commit: michaelni <[email protected]>
CommitDate: Thu Aug 27 14:44:32 2026 +0000
avformat/movenc: fix crash when flushing a fragment with no data
mov_flush_fragment() calls ffio_reset_dyn_buf() on mov->mdat_buf when
writing the initial moov. That buffer is allocated lazily on the first
packet, so it is still NULL when the trailer is written before anything
was muxed, and ffio_reset_dyn_buf() dereferences it.
627da1111c9d replaced ffio_free_dyn_buf(), which tolerates NULL, with
ffio_reset_dyn_buf(), which does not, turning this case into a crash.
This affects every fragmented mode that defers the initial moov to the
first flush.
Skip the block entirely when the buffer was never opened. Nothing
references the empty mdat it would otherwise write, as no samples were
muxed.
Reproduced with:
ffmpeg -f lavfi -i color=s=64x64 -frames:v 0 -movflags +frag_keyframe
out.mp4
Fixes: 627da1111c9d ("libavformat/movenc: Uses dynamic buffers for
fragmented chunks")
Signed-off-by: Ackanir <[email protected]>
---
libavformat/movenc.c | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)
diff --git a/libavformat/movenc.c b/libavformat/movenc.c
index 14504d0947..4c7868c5f8 100644
--- a/libavformat/movenc.c
+++ b/libavformat/movenc.c
@@ -6804,11 +6804,13 @@ static int mov_flush_fragment(AVFormatContext *s, int
force)
return 0;
}
- buf_size = avio_get_dyn_buf(mov->mdat_buf, &buf);
- avio_wb32(s->pb, buf_size + 8);
- ffio_wfourcc(s->pb, "mdat");
- avio_write(s->pb, buf, buf_size);
- ffio_reset_dyn_buf(mov->mdat_buf);
+ if (mov->mdat_buf) {
+ buf_size = avio_get_dyn_buf(mov->mdat_buf, &buf);
+ avio_wb32(s->pb, buf_size + 8);
+ ffio_wfourcc(s->pb, "mdat");
+ avio_write(s->pb, buf, buf_size);
+ ffio_reset_dyn_buf(mov->mdat_buf);
+ }
if (mov->flags & FF_MOV_FLAG_GLOBAL_SIDX)
mov->reserved_header_pos = avio_tell(s->pb);
--
To stop receiving notification emails like this one, please contact
[email protected].
_______________________________________________
ffmpeg-cvslog mailing list -- [email protected]
To unsubscribe send an email to [email protected]
