From 754189f9cf1ef9705689c0594bf1e377d446e861 Mon Sep 17 00:00:00 2001
From: Lennart Poettering <lennart@poettering.net>
Date: Fri, 11 May 2012 17:17:57 +0200
Subject: [PATCH] core: add extra safety check before switching root (cherry
 picked from commit
 50913bc0c8ced894ceabc7e893c0fdf73af9a261)

---
 src/core/dbus-manager.c |   17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/src/core/dbus-manager.c b/src/core/dbus-manager.c
index adbef55..802389c 100644
--- a/src/core/dbus-manager.c
+++ b/src/core/dbus-manager.c
@@ -1188,6 +1188,7 @@ static DBusHandlerResult bus_manager_message_handler(DBusConnection *connection,
         } else if (dbus_message_is_method_call(message, "org.freedesktop.systemd1.Manager", "SwitchRoot")) {
                 const char *switch_root, *switch_root_init;
                 char *u, *v;
+                int k;
 
                 if (!dbus_message_get_args(
                                     message,
@@ -1208,6 +1209,22 @@ static DBusHandlerResult bus_manager_message_handler(DBusConnection *connection,
                         return bus_send_error_reply(connection, message, &error, -ENOTSUP);
                 }
 
+                /* Safety check */
+                if (isempty(switch_root_init))
+                        k = access(switch_root, F_OK);
+                else {
+                        char *p;
+
+                        p = join(switch_root, "/", switch_root_init, NULL);
+                        if (!p)
+                                goto oom;
+
+                        k = access(p, X_OK);
+                        free(p);
+                }
+                if (k < 0)
+                        return bus_send_error_reply(connection, message, NULL, -errno);
+
                 u = strdup(switch_root);
                 if (!u)
                         goto oom;