Fix segfault in MCM FFmpeg plugin occurred in memcpy

In mcm_read_packet() the length of the buffer received from
media_proxy can be smaller than the configured frame size.
Passing the size argument to memcpy() being larger than the
source buffer size can lead to a segmentation fault.

This commit fixes this issue by passing the size argument to
memcpy() as the lowest value between the configured frame
size and the actual Rx buffer length.

Signed-off-by: Konstantin Ilichev <[email protected]>

ffmpeg-plugin/mcm_rx.c

@@ -209,7 +209,7 @@ static int mcm_read_packet(AVFormatContext* avctx, AVPacket* pkt)
     if ((ret = av_new_packet(pkt, s->frame_size)) < 0)
         return ret;
 
-    memcpy(pkt->data, buf->data, s->frame_size);
+    memcpy(pkt->data, buf->data, FFMIN(s->frame_size, buf->len));
 
     pkt->pts = pkt->dts = AV_NOPTS_VALUE;