On 7/12/2020 8:11 PM, Andriy Gelman wrote: > On Wed, 24. Jun 09:26, Andriy Gelman wrote: >> On Mon, 25. May 14:59, Andriy Gelman wrote: >>> On Sat, 16. May 11:53, Andriy Gelman wrote: >>>> On Sat, 09. May 13:35, Andriy Gelman wrote: >>>>> 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 >>>>> >>>> >>>> ping >>>> >>> >>> ping >>> >> >> ping >> > > The patch has been on the ml for a long time so I'd like to apply it soon. > It gets rid of a seg fault in: > https://trac.ffmpeg.org/ticket/8774 > > Any objections?
If you maintain this code and get no reviews, then you can push it after a while. No need to wait two months. I can't test it, but should be ok. _______________________________________________ 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".
