The extradata allocated in mov_write_single_packet() for AV1 was missing
the required AV_INPUT_BUFFER_PADDING_SIZE padding bytes. This could lead
to out-of-bounds reads when the extradata is parsed by bitstream readers.
Replace av_memdup() with av_malloc() + memset() + memcpy() to ensure
proper padding is present and zeroed.
Reproduced with:
./ffmpeg -y -f lavfi -i "testsrc=duration=1:size=320x240:rate=30" -c:v libaom-av1 -cpu-used 8 -crf 50 test-av1.mp4
Signed-off-by: Jun Zhao <barryjzhao@tencent.com>
