audio: st_rate_flow exist a infinite loop

If a voice recording equipment is opened for a long time(several days)
in windows guest, rate->ipos will overflow and rate->opos will never
have a chance to change. It will result to a infinite loop.

Signed-off-by: Peng Hao <peng.hao2@zte.com.cn>
Signed-off-by: Wang Yechao <wang.yechao255@zte.com.cn>
Message-id: 1500128061-20849-1-git-send-email-peng.hao2@zte.com.cn
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

audio/rate_template.h

@@ -71,6 +71,12 @@ void NAME (void *opaque, struct st_sample *ibuf, struct st_sample *obuf,
         while (rate->ipos <= (rate->opos >> 32)) {
             ilast = *ibuf++;
             rate->ipos++;
+
+            /* if ipos overflow, there is  a infinite loop */
+            if (rate->ipos == 0xffffffff) {
+                rate->ipos = 1;
+                rate->opos = rate->opos & 0xffffffff;
+            }
             /* See if we finished the input buffer yet */
             if (ibuf >= iend) {
                 goto the_end;