tty: Verify active pairs once dump complete

We don't support yet detached terminals migration,
so fail early if we can't proceed.
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Acked-by: Andrew Vagin <avagin@parallels.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

cr-dump.c

@@ -1630,6 +1630,10 @@ int cr_dump_tasks(pid_t pid, const struct cr_options *opts)
 	if (ret)
 		goto err;
 
+	ret = tty_verify_active_pairs();
+	if (ret)
+		goto err;
+
 	fd_id_show_tree();
 err:
 	close_cr_fdset(&glob_fdset);

include/tty.h

@@ -18,4 +18,6 @@ extern int collect_tty(void);
 extern int prepare_shared_tty(void);
 extern void tty_setup_slavery(void);
 
+extern int tty_verify_active_pairs(void);
+
 #endif /* CR_TTY_H__ */

tty.c

@@ -138,6 +138,29 @@ static int tty_gen_id(int major, int index)
 	return (index << 1) + (major == TTYAUX_MAJOR);
 }
 
+static int tty_get_index(u32 id)
+{
+	return id >> 1;
+}
+
+/* Make sure the active pairs do exist */
+int tty_verify_active_pairs(void)
+{
+	int i;
+
+	for (i = 0; i < (MAX_TTYS << 1); i += 2) {
+		if (test_bit(i, tty_active_pairs) &&
+		    !test_bit(i + 1, tty_active_pairs)) {
+			pr_err("Found slave peer index %d without "
+				"correspond master peer\n",
+				tty_get_index(i));
+			return -1;
+		}
+	}
+
+	return 0;
+}
+
 static int parse_index(u32 id, int lfd, int major)
 {
 	int index = -1;