On Sun, Feb 9, 2025 at 5:43 AM Frank Plowman <post@frankplowman.com> wrote:

In the fail: block of decode_nal_units, a check as to whether fc->ref is nonzero is used. Before this patch, fc->ref was set to NULL in frame_context_setup. The issue is that, by the time frame_context_setup is called, falliable functions (namely slices_realloc and ff_vvc_decode_frame_ps) have already been called. Therefore, there could arise a situation in which the fc->ref test of decode_nal_units' fail: block is performed while fc->ref has an invalid value. This seems to be particularly prevalent in situations where the FrameContexts are being reused. The patch resolves the issue by moving the assignment of fc->ref to NULL to the very top of decode_nal_units, before any falliable functions are called.

Thank you, Frank. Applied.

Signed-off-by: Frank Plowman <post@frankplowman.com> --- libavcodec/vvc/dec.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/libavcodec/vvc/dec.c b/libavcodec/vvc/dec.c index 51dd60ae92..572e904301 100644 --- a/libavcodec/vvc/dec.c +++ b/libavcodec/vvc/dec.c @@ -671,8 +671,6 @@ static int frame_context_setup(VVCFrameContext *fc, VVCContext *s) { int ret;

- fc->ref = NULL; - // copy refs from the last frame if (s->nb_frames && s->nb_fcs > 1) { VVCFrameContext *prev = get_frame_context(s, fc, -1); @@ -927,6 +925,7 @@ static int decode_nal_units(VVCContext *s, VVCFrameContext *fc, AVPacket *avpkt) int ret = 0; s->last_eos = s->eos; s->eos = 0; + fc->ref = NULL;

ff_cbs_fragment_reset(frame); ret = ff_cbs_read_packet(s->cbc, frame, avpkt); -- 2.47.0