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[90.183.112.6]) by smtp.gmail.com with ESMTPSA id h29sm1706926wrf.76.2017.09.20.06.20.54 (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Wed, 20 Sep 2017 06:20:55 -0700 (PDT) From: Jaroslav Beran To: ffmpeg-devel@ffmpeg.org Date: Wed, 20 Sep 2017 15:14:54 +0200 Message-Id: <20170920131454.8727-1-jara.beran@gmail.com> X-Mailer: git-send-email 2.13.5 X-Mailman-Approved-At: Fri, 22 Sep 2017 03:35:19 +0300 Subject: [FFmpeg-devel] [PATCH] libavdevice/v4l2: fix invalid access to struct v4l2_buffer X-BeenThere: ffmpeg-devel@ffmpeg.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: FFmpeg development discussions and patches List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: FFmpeg development discussions and patches Cc: Jaroslav Beran MIME-Version: 1.0 Errors-To: ffmpeg-devel-bounces@ffmpeg.org Sender: "ffmpeg-devel" In case we are short of queued buffers, at first v4l2_buffer was enqueued to kernel so it's not owned by user-space anymore. After that it's timestamp field was read, but it might be overwritten by driver at that moment. It resulted in invalid timestamp sometimes. --- libavdevice/v4l2.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/libavdevice/v4l2.c b/libavdevice/v4l2.c index 17451cdb60..f087badf5c 100644 --- a/libavdevice/v4l2.c +++ b/libavdevice/v4l2.c @@ -492,6 +492,7 @@ static int mmap_read_frame(AVFormatContext *ctx, AVPacket *pkt) .type = V4L2_BUF_TYPE_VIDEO_CAPTURE, .memory = V4L2_MEMORY_MMAP }; + struct timeval buf_ts; int res; pkt->size = 0; @@ -508,6 +509,8 @@ static int mmap_read_frame(AVFormatContext *ctx, AVPacket *pkt) return res; } + buf_ts = buf.timestamp; + if (buf.index >= s->buffers) { av_log(ctx, AV_LOG_ERROR, "Invalid buffer index received.\n"); return AVERROR(EINVAL); @@ -583,7 +586,7 @@ static int mmap_read_frame(AVFormatContext *ctx, AVPacket *pkt) return AVERROR(ENOMEM); } } - pkt->pts = buf.timestamp.tv_sec * INT64_C(1000000) + buf.timestamp.tv_usec; + pkt->pts = buf_ts.tv_sec * INT64_C(1000000) + buf_ts.tv_usec; convert_timestamp(ctx, &pkt->pts); return pkt->size;