util: Check for overflow in read_fd_link

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

util.c

@@ -430,6 +430,9 @@ int read_fd_link(int lfd, char *buf, size_t size)
 	if (ret < 0) {
 		pr_perror("Can't read link of fd %d", lfd);
 		return -1;
+	} else if ((size_t)ret == size) {
+		pr_err("Buffer for read link of fd %d is too small\n", lfd);
+		return -1;
 	}
 	buf[ret] = 0;