logind: fail on CreateSession if already in session

Right now, if you're already in a session and call CreateSession, we
return information about the current session of yours. This is highy
confusing and a nasty hack. Avoid that, and instead return a commonly
known error, so the caller can detect that.

This has the side-effect, that we no longer override XDG_VTNR and XDG_SEAT
in pam_systemd, if you're already in a session. But this sounds like the
right thing to do, anyway.

1 files changed, 2 insertions, 2 deletions

diff --git a/src/login/logind-core.c b/src/login/logind-core.c
index a6c01f7d85..96a20e27b9 100644
--- a/src/login/logind-core.c
+++ b/src/login/logind-core.c
@@ -317,7 +317,6 @@ int manager_get_session_by_pid(Manager *m, pid_t pid, Session **session) {
         int r;
 
         assert(m);
-        assert(session);
 
         if (pid < 1)
                 return -EINVAL;
@@ -330,7 +329,8 @@ int manager_get_session_by_pid(Manager *m, pid_t pid, Session **session) {
         if (!s)
                 return 0;
 
-        *session = s;
+        if (session)
+                *session = s;
         return 1;
 }