[systemd-devel] [PATCH 2/3] logind: session: set_controller should fail if prepare_vt fails

[Olivier Brunel]

If controllers can expect logind to have "prepared" the VT (e.g. set it to
graphics mode, etc) then TakeControl() should fail if said preparation
failed (and session_restore_vt() was called).
---
 src/login/logind-session.c | 15 +++++++++------
 src/login/logind-session.h |  2 +-
 2 files changed, 10 insertions(+), 7 deletions(-)

diff --git a/src/login/logind-session.c b/src/login/logind-session.c
index 905e73f..3f4e177 100644
--- a/src/login/logind-session.c
+++ b/src/login/logind-session.c
@@ -1003,14 +1003,14 @@ static int session_vt_fn(sd_event_source *source, const struct signalfd_siginfo
         return 0;
 }
 
-void session_prepare_vt(Session *s) {
+int session_prepare_vt(Session *s) {
         int vt, r;
         struct vt_mode mode = { 0 };
         sigset_t mask;
 
         vt = session_open_vt(s);
         if (vt < 0)
-                return;
+                return vt;
 
         r = fchown(vt, s->user->uid, -1);
         if (r < 0)
@@ -1042,11 +1042,12 @@ void session_prepare_vt(Session *s) {
         if (r < 0)
                 goto error;
 
-        return;
+        return 0;
 
 error:
         log_error("cannot mute VT %u for session %s (%d/%d)", s->vtnr, s->id, r, errno);
         session_restore_vt(s);
+        return r;
 }
 
 void session_restore_vt(Session *s) {
@@ -1123,8 +1124,6 @@ int session_set_controller(Session *s, const char *sender, bool force) {
                 return r;
         }
 
-        session_swap_controller(s, t);
-
         /* When setting a session controller, we forcibly mute the VT and set
          * it into graphics-mode. Applications can override that by changing
          * VT state after calling TakeControl(). However, this serves as a good
@@ -1133,7 +1132,11 @@ int session_set_controller(Session *s, const char *sender, bool force) {
          * exits.
          * If logind crashes/restarts, we restore the controller during restart
          * or reset the VT in case it crashed/exited, too. */
-        session_prepare_vt(s);
+        r = session_prepare_vt(s);
+        if (r < 0)
+                return r;
+
+        session_swap_controller(s, t);
 
         return 0;
 }
diff --git a/src/login/logind-session.h b/src/login/logind-session.h
index e62b76d..2ab3182 100644
--- a/src/login/logind-session.h
+++ b/src/login/logind-session.h
@@ -172,7 +172,7 @@ SessionClass session_class_from_string(const char *s) _pure_;
 const char *kill_who_to_string(KillWho k) _const_;
 KillWho kill_who_from_string(const char *s) _pure_;
 
-void session_prepare_vt(Session *s);
+int session_prepare_vt(Session *s);
 void session_restore_vt(Session *s);
 
 bool session_is_controller(Session *s, const char *sender);
-- 
2.0.4