lavf/webm_chunk: Fix NULL dereference
The earlier version of the webm_chunk muxer had several bugs:
1. If the first packet of an audio stream didn't have a PTS of zero,
then no chunk will be started before a packet is delivered to the
underlying Matroska/WebM muxer, i.e. the AVFormatContext used to write
these packets had a NULL as AVIOContext for output. This is behind the
crash in ticket #5752.
2. If an error happens during writing a packet, the underlyimg
Matroska/WebM muxer context is freed. This leads to a use-after-free
coupled with a double-free in webm_chunk_write_trailer (which supposes
that the underlying AVFormatContext is still valid).
3. Even when no error occurs at all, webm_chunk_write_trailer is still
buggy: After the underlying Matroska/WebM muxer has written its trailer,
ending the chunk implicitly flushes it again which is illegal at this
point.
These bugs have been fixed.
Fixes #5752.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
(cherry picked from commit
8c6ee7626bcce7c270360f33b60dc7ef99939fc3)
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
git.videolan.org / ffmpeg.git / commit