Bug 90818

Summary:	logind: Save the user’s state when a session enters SESSION_ACTIVE
Product:	systemd	Reporter:	Philip Withnall <bugzilla>
Component:	general	Assignee:	systemd-bugs
Status:	RESOLVED FIXED	QA Contact:	systemd-bugs
Severity:	normal
Priority:	medium	CC:	dh.herrmann
Version:	unspecified
Hardware:	All
OS:	All
Whiteboard:
i915 platform:		i915 features:
Attachments:	logind: Save the user’s state when a session enters SESSION_ACTIVE

Description Philip Withnall 2015-06-02 13:24:46 UTC

Patch coming to fix login’s STATE tracking for users to be correct when starting a new session on a VT switch. This is important for PolicyKit decisions about whether the user is active or online, as it affects the return value of sd_uid_get_state().

See the commit message for full details.

See also: bug #90769, bug #67728, bug #76358.

---

The incorrect behaviour can be tested by:
 1. In an X11 terminal, `cat /run/systemd/users/$uid` gives SESSIONS=1 STATE=active.
 2. Switch VT, log in, `cat /run/systemd/users/$uid` gives SESSIONS="c2 1" STATE=online.
 3. Switch back to X11 and cat again, gives SESSIONS="c2 1" STATE=active.
 4. Switch back to VT and cat again, gives SESSIONS="c2 1" STATE=active.

With some debugging logging added to logind, it seems that when switching to the VT (step #2 above):
 A. Session 1 is switched from SESSION_ACTIVE to SESSION_ONLINE because of the VT change.
 B. A new session (c2) is created, with initial state SESSION_OPENING.
 C. user_save() is called, which takes the maximum state of sessions 1 and c2, which is SESSION_ONLINE.
 D. user_save() is not called again after session c2 switches from SESSION_OPENING to SESSION_ACTIVE.

Comment 1 Philip Withnall 2015-06-02 13:24:48 UTC

Created attachment 116244 [details] [review]
logind: Save the user’s state when a session enters SESSION_ACTIVE

When (for example) switching from X11 to a new VT and logging in there,
creating a new session, the user state file (/run/systemd/users/$uid) is
not updated after the session becomes active. The latest time it is
saved is when the session is in SESSION_OPENING.

This results in a /run/systemd/users/$uid file which contains
STATE=online for the current user on the current active VT, which is
obviously wrong.

As functions like sd_uid_get_state() use this file to get the user’s
state, this could result in things like PolicyKit making incorrect
decisions about the user’s state. (See
https://bugs.freedesktop.org/show_bug.cgi?id=76358.)

Fix this by re-saving the state for a session’s user after completing
the state_job for that session.

Comment 2 David Herrmann 2015-06-04 14:59:06 UTC

Applied, thanks!

Comment 3 Philip Withnall 2015-06-04 15:26:04 UTC

(In reply to David Herrmann from comment #2)
> Applied, thanks!

(For posterity, the review is on https://github.com/systemd/systemd/pull/58.)

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