logind: allow greeters to take over VTs

Make sure a greeter can forcefully spawn a session on a VT that is
in-use. A recent patch prevented this (this used to be possible for all
session types) as it is highly fragile. However, as it turns out,
greeters seem to rely on that feature. Therefore, make sure we allow it
explicitly for greeters.

diff --git a/src/login/logind-dbus.c b/src/login/logind-dbus.c
index cd9cab7..ca435df 100644 (file)
--- a/src/login/logind-dbus.c
+++ b/src/login/logind-dbus.c
@@ -699,9 +699,12 @@ static int method_create_session(sd_bus_message *message, void *userdata, sd_bus
          * after the user-session and want the user-session to take
          * over the VT. We need to support this for
          * backwards-compatibility, so make sure we allow new sessions
-         * on a VT that a greeter is running on.
+         * on a VT that a greeter is running on. Furthermore, to allow
+         * re-logins, we have to allow a greeter to take over a used VT for
+         * the exact same reasons.
          */
-        if (vtnr > 0 &&
+        if (c != SESSION_GREETER &&
+            vtnr > 0 &&
             vtnr < m->seat0->position_count &&
             m->seat0->positions[vtnr] &&
             m->seat0->positions[vtnr]->class != SESSION_GREETER)