From: Andriy Gelman <andriy.gel...@gmail.com> v4l2_receive_frame() uses two packets s->buf_pkt and avpkt. If avpkt cannot be enqueued, the packet is buffered in s->buf_pkt and enqueued in the next call. Currently the ownership transfer between the two packets is not properly handled. A double free occurs if ff_v4l2_context_enqueue_packet() returns EAGAIN and v4l2_try_start returns EINVAL.
In fact, having two AVPackets is not needed and everything can be handled by s->buf_pkt. This commit removes the local avpkt from v4l2_receive_frame(), meaning that the ownership transfer doesn't need to be handled and the double free is fixed. Signed-off-by: Andriy Gelman <andriy.gel...@gmail.com> --- Sorry, forgot to squash the commit from v1 so v2 didn't apply. This is correct version. Supersedes: https://patchwork.ffmpeg.org/project/ffmpeg/patch/20200505055454.28683-1-andriy.gel...@gmail.com/ libavcodec/v4l2_m2m_dec.c | 37 +++++++++++++++---------------------- 1 file changed, 15 insertions(+), 22 deletions(-) diff --git a/libavcodec/v4l2_m2m_dec.c b/libavcodec/v4l2_m2m_dec.c index 3e17e0fcac..b038efed9c 100644 --- a/libavcodec/v4l2_m2m_dec.c +++ b/libavcodec/v4l2_m2m_dec.c @@ -138,14 +138,10 @@ static int v4l2_receive_frame(AVCodecContext *avctx, AVFrame *frame) V4L2m2mContext *s = ((V4L2m2mPriv*)avctx->priv_data)->context; V4L2Context *const capture = &s->capture; V4L2Context *const output = &s->output; - AVPacket avpkt = {0}; int ret; - if (s->buf_pkt.size) { - avpkt = s->buf_pkt; - memset(&s->buf_pkt, 0, sizeof(AVPacket)); - } else { - ret = ff_decode_get_packet(avctx, &avpkt); + if (!s->buf_pkt.size) { + ret = ff_decode_get_packet(avctx, &s->buf_pkt); if (ret < 0 && ret != AVERROR_EOF) return ret; } @@ -153,32 +149,29 @@ static int v4l2_receive_frame(AVCodecContext *avctx, AVFrame *frame) if (s->draining) goto dequeue; - ret = ff_v4l2_context_enqueue_packet(output, &avpkt); - if (ret < 0) { - if (ret != AVERROR(EAGAIN)) - return ret; + ret = ff_v4l2_context_enqueue_packet(output, &s->buf_pkt); + if (ret < 0 && ret != AVERROR(EAGAIN)) + goto fail; - s->buf_pkt = avpkt; - /* no input buffers available, continue dequeing */ - } + /* if EAGAIN don't unref packet and try to enqueue in the next iteration */ + if (ret != AVERROR(EAGAIN)) + av_packet_unref(&s->buf_pkt); - if (avpkt.size) { + if (!s->draining) { ret = v4l2_try_start(avctx); if (ret) { - av_packet_unref(&avpkt); - /* cant recover */ - if (ret == AVERROR(ENOMEM)) - return ret; - - return 0; + if (ret != AVERROR(ENOMEM)) + ret = 0; + goto fail; } } dequeue: - if (!s->buf_pkt.size) - av_packet_unref(&avpkt); return ff_v4l2_context_dequeue_frame(capture, frame, -1); +fail: + av_packet_unref(&s->buf_pkt); + return ret; } static av_cold int v4l2_decode_init(AVCodecContext *avctx) -- 2.25.1 _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
