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libavdevice/v4l2: fix invalid access to struct v4l2_buffer

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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.

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
This commit is contained in:
Jaroslav Beran 2017-09-20 15:14:54 +02:00 committed by Michael Niedermayer
parent 5a9415533d
commit 00a1e1337f
1 changed files with 4 additions and 1 deletions
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5
libavdevice/v4l2.c
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@ -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;