properly handle signed integer input

git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.0@45336 65c4cc65-6c06-0410-ace0-fbb531ad65f3

channels/chan_skinny.c

@@ -2305,6 +2305,10 @@ static int get_input(struct skinnysession *s)
 			return -1;
 		}
 		dlen = *(int *)s->inbuf;
+		if (dlen < 0) {
+			ast_log(LOG_WARNING, "Skinny Client sent invalid data.\n");
+			return -1;
+		}
 		if (dlen+8 > sizeof(s->inbuf))
 			dlen = sizeof(s->inbuf) - 8;
 		res = read(s->fd, s->inbuf+4, dlen+4);