CVE-2014-7824: set fd rlimit to 64k for the system dbus-daemon

This ensures that our rlimit is actually high enough to avoid the
denial of service described in CVE-2014-3636 part A.
CVE-2014-7824 has been allocated for this incomplete fix.

Restore the original rlimit for activated services, to avoid
them getting undesired higher limits.

(Thanks to Alban Crequy for various adjustments which have been
included in this commit.)

Bug: https://bugs.freedesktop.org/show_bug.cgi?id=85105
Reviewed-by: Alban Crequy <alban.crequy@collabora.co.uk>

1 files changed, 27 insertions, 1 deletions

diff --git a/bus/activation.c b/bus/activation.c
index 149cca8a..ecd19bb4 100644
--- a/bus/activation.c
+++ b/bus/activation.c
@@ -1688,6 +1688,31 @@ out:
   return retval;
 }
 
+static void
+child_setup (void *user_data)
+{
+#ifdef DBUS_UNIX
+  BusActivation *activation = user_data;
+  DBusRLimit *initial_fd_limit;
+  DBusError error;
+
+  dbus_error_init (&error);
+  initial_fd_limit = bus_context_get_initial_fd_limit (activation->context);
+
+  if (initial_fd_limit != NULL &&
+      !_dbus_rlimit_restore_fd_limit (initial_fd_limit, &error))
+    {
+      /* unfortunately we don't actually know the service name here */
+      bus_context_log (activation->context,
+                       DBUS_SYSTEM_LOG_INFO,
+                       "Failed to reset fd limit before activating "
+                       "service: %s: %s",
+                       error.name, error.message);
+    }
+#endif
+}
+
+
 dbus_bool_t
 bus_activation_activate_service (BusActivation  *activation,
                                  DBusConnection *connection,
@@ -2121,7 +2146,8 @@ bus_activation_activate_service (BusActivation  *activation,
                                           service_name,
                                           argv,
                                           envp,
-                                          NULL, activation,
+                                          child_setup,
+                                          activation,
                                           &tmp_error))
     {
       _dbus_verbose ("Failed to spawn child\n");