#5 Add patch to fix fast user switching
Merged 3 years ago by catanzaro. Opened 3 years ago by benzea.
rpms/ benzea/gdm fix-1751673  into  master

@@ -0,0 +1,141 @@ 

+ From fd6736eb357100ce121762c386592e7703db71e0 Mon Sep 17 00:00:00 2001

+ From: Benjamin Berg <bberg@redhat.com>

+ Date: Wed, 25 Sep 2019 14:51:40 +0200

+ Subject: [PATCH] gdm-session-worker: Drop login_vt assuming it is

+  GDM_INITIAL_VT

+ 

+ When a session ends, its "session worker" is closed. Since

+ 3e8220921bb608afd06ed677104fd2244b901a28 (3.33.4), we uninitialise PAM

+ when this happens. As part of this procedure, we jump back to the login

+ screen, if the screen being killed is not itself the login screen.

+ 

+ This has broken fast user switching. It goes like this - this

+ explanation is a bit complicated, bear with us:

+ 

+ We want to jump back to the login screen when a normal user session

+ ends, so that people can log in again. We do not want to do this when a

+ login screen itself ends. When session workers start up, they query for

+ the *currently active VT* and save this in `login_vt`. Then later on, we

+ check if our session ID is the same as `login_vt`, and jump to

+ `login_vt` if they are different - this means that it was a user session

+ not a login session. Querying the currently active VT is fine for the

+ first greeter, but when initiating a user switch it's wrong as this

+ gives the user VT.

+ 

+ GDM greeters are killed once they have spawned a session. They are

+ associated with a logind session, and therefore a PAM session. There are

+ some actions performed when unregistering PAM sessions, including the

+ previously mentioned VT jump. Before

+ 3e8220921bb608afd06ed677104fd2244b901a28 we only uninitialised PAM when

+ the session itself exited so the bug was masked, but now (since this

+ commit), if the login screen's *worker* exits first - as happens in the

+ normal case when GDM kills it - we also do this uninitialisation. Since

+ we falsely recorded the login screen as the first user's VT, this means

+ that checking `login_vt != session_vt` returns `TRUE` and we jump back

+ to the previous user's session immediately after logging into the new

+ session: fast user switching is broken.

+ 

+ Since the work on shutting down the GDM session has been finished, we

+ can assume that the login_vt is always on GDM_INITIAL_VT (see

+ example c71bc5d6c3bc2ec448b5c72ce9a811d9c0c7905e

+ "local-display-factory: Remove initial VT is in use check" and

+ 39fb4ff64e6a0653e70a3bfab31da47b49227d59 "manager: don't run autologin

+ display on tty1"). So simply replace all usages of login_vt with

+ GDM_INITIAL_VT to solve the above problem.

+ 

+ Note that in the case where ENABLE_USER_DISPLAY_SERVER is not enabled,

+ the login_vt is always the same as the session_vt. We can simply remove

+ the VT switching magic there and everything should be working as

+ expected.

+ 

+ This is a simpler version of the patch by Iain Lane <iainl@gnome.org>,

+ taking into account that we can make the assumption about the login_vt.

+ 

+ Closes #515

+ ---

+  daemon/gdm-session-worker.c | 43 +++++++------------------------------

+  1 file changed, 8 insertions(+), 35 deletions(-)

+ 

+ diff --git a/daemon/gdm-session-worker.c b/daemon/gdm-session-worker.c

+ index 0e854158..4f9083c3 100644

+ --- a/daemon/gdm-session-worker.c

+ +++ b/daemon/gdm-session-worker.c

+ @@ -146,7 +146,6 @@ struct GdmSessionWorkerPrivate

+          char            **extensions;

+  

+          int               cred_flags;

+ -        int               login_vt;

+          int               session_vt;

+          int               session_tty_fd;

+  

+ @@ -1052,13 +1051,15 @@ gdm_session_worker_uninitialize_pam (GdmSessionWorker *worker,

+  

+          gdm_session_worker_stop_auditor (worker);

+  

+ +#ifdef ENABLE_USER_DISPLAY_SERVER

+          if (g_strcmp0 (worker->priv->display_seat_id, "seat0") == 0) {

+ -                if (worker->priv->login_vt != worker->priv->session_vt) {

+ -                        jump_to_vt (worker, worker->priv->login_vt);

+ +                /* Switch to the login VT if we are not the login screen. */

+ +                if (worker->priv->session_vt != GDM_INITIAL_VT) {

+ +                        jump_to_vt (worker, GDM_INITIAL_VT);

+                  }

+          }

+ +#endif

+  

+ -        worker->priv->login_vt = 0;

+          worker->priv->session_vt = 0;

+  

+          g_debug ("GdmSessionWorker: state NONE");

+ @@ -1107,32 +1108,6 @@ _get_xauth_for_pam (const char *x11_authority_file)

+  }

+  #endif

+  

+ -static gboolean

+ -ensure_login_vt (GdmSessionWorker *worker)

+ -{

+ -        int fd;

+ -        struct vt_stat vt_state = { 0 };

+ -        gboolean got_login_vt = FALSE;

+ -

+ -        fd = open ("/dev/tty0", O_RDWR | O_NOCTTY);

+ -

+ -        if (fd < 0) {

+ -                g_debug ("GdmSessionWorker: couldn't open VT master: %m");

+ -                return FALSE;

+ -        }

+ -

+ -        if (ioctl (fd, VT_GETSTATE, &vt_state) < 0) {

+ -                g_debug ("GdmSessionWorker: couldn't get current VT: %m");

+ -                goto out;

+ -        }

+ -

+ -        worker->priv->login_vt = vt_state.v_active;

+ -        got_login_vt = TRUE;

+ -out:

+ -        close (fd);

+ -        return got_login_vt;

+ -}

+ -

+  static gboolean

+  gdm_session_worker_initialize_pam (GdmSessionWorker   *worker,

+                                     const char         *service,

+ @@ -1227,12 +1202,10 @@ gdm_session_worker_initialize_pam (GdmSessionWorker   *worker,

+          g_debug ("GdmSessionWorker: state SETUP_COMPLETE");

+          gdm_session_worker_set_state (worker, GDM_SESSION_WORKER_STATE_SETUP_COMPLETE);

+  

+ -        /* Temporarily set PAM_TTY with the currently active VT (login screen) 

+ +        /* Temporarily set PAM_TTY with the login VT,

+             PAM_TTY will be reset with the users VT right before the user session is opened */

+ -        if (ensure_login_vt (worker)) {

+ -                g_snprintf (tty_string, 256, "/dev/tty%d", worker->priv->login_vt);

+ -                pam_set_item (worker->priv->pam_handle, PAM_TTY, tty_string);

+ -        }

+ +        g_snprintf (tty_string, 256, "/dev/tty%d", GDM_INITIAL_VT);

+ +        pam_set_item (worker->priv->pam_handle, PAM_TTY, tty_string);

+          if (!display_is_local)

+                  worker->priv->password_is_required = TRUE;

+  

+ -- 

+ 2.21.0

+ 

file modified
+7 -1
@@ -10,7 +10,7 @@ 

  Name: gdm

  Epoch: 1

  Version: 3.34.0

- Release: 1%{?dist}

+ Release: 2%{?dist}

  Summary: The GNOME Display Manager

  

  License: GPLv2+
@@ -20,6 +20,7 @@ 

  Patch0: 0001-Honor-initial-setup-being-disabled-by-distro-install.patch

  

  Patch10001: 0001-data-disable-wayland-if-modesetting-is-disabled.patch

+ Patch10002: 0001-gdm-session-worker-Drop-login_vt-assuming-it-is-GDM_.patch

  

  Patch99: system-dconf.patch

  
@@ -311,6 +312,11 @@ 

  %{_libdir}/pkgconfig/gdm-pam-extensions.pc

  

  %changelog

+ * Wed Sep 25 2019 Benjamin Berg <bberg@redhat.com> - 1:3.34.0-2

+ - Add patch to fix fast user switching

+   https://gitlab.gnome.org/GNOME/gdm/merge_requests/86

+ - Resolves: #1751673

+ 

  * Wed Sep 11 2019 Kalev Lember <klember@redhat.com> - 1:3.34.0-1

  - Update to 3.34.0