chiark / gitweb /
logind: get a fresh file descriptor to clean up a VT
[elogind.git] / src / login / logind-session.c
index beaa601..1a5c76b 100644 (file)
@@ -28,9 +28,7 @@
 #include <sys/ioctl.h>
 #include <unistd.h>
 
-#include "sd-id128.h"
 #include "sd-messages.h"
-#include "strv.h"
 #include "util.h"
 #include "mkdir.h"
 #include "path-util.h"
 #include "bus-util.h"
 #include "bus-error.h"
 #include "logind-session.h"
+#include "formats-util.h"
+#include "terminal-util.h"
 
-static unsigned devt_hash_func(const void *p) {
-        uint64_t u = *(const dev_t*)p;
+#define RELEASE_USEC (20*USEC_PER_SEC)
 
-        return uint64_hash_func(&u);
-}
-
-static int devt_compare_func(const void *_a, const void *_b) {
-        dev_t a, b;
-
-        a = *(const dev_t*) _a;
-        b = *(const dev_t*) _b;
-
-        return a < b ? -1 : (a > b ? 1 : 0);
-}
+static void session_remove_fifo(Session *s);
 
 Session* session_new(Manager *m, const char *id) {
         Session *s;
@@ -72,14 +61,14 @@ Session* session_new(Manager *m, const char *id) {
                 return NULL;
         }
 
-        s->devices = hashmap_new(devt_hash_func, devt_compare_func);
+        s->devices = hashmap_new(&devt_hash_ops);
         if (!s->devices) {
                 free(s->state_file);
                 free(s);
                 return NULL;
         }
 
-        s->id = path_get_file_name(s->state_file);
+        s->id = basename(s->state_file);
 
         if (hashmap_put(m->sessions, s->id, s) < 0) {
                 hashmap_free(s->devices);
@@ -103,6 +92,8 @@ void session_free(Session *s) {
         if (s->in_gc_queue)
                 LIST_REMOVE(gc_queue, s->manager->session_gc_queue, s);
 
+        s->timer_event_source = sd_event_source_unref(s->timer_event_source);
+
         session_remove_fifo(s);
 
         session_drop_controller(s);
@@ -125,6 +116,7 @@ void session_free(Session *s) {
                 if (s->seat->pending_switch == s)
                         s->seat->pending_switch = NULL;
 
+                seat_evict_position(s->seat, s);
                 LIST_REMOVE(sessions_by_seat, s->seat->sessions, s);
         }
 
@@ -142,6 +134,7 @@ void session_free(Session *s) {
         free(s->remote_host);
         free(s->remote_user);
         free(s->service);
+        free(s->desktop);
 
         hashmap_remove(s->manager->sessions, s->id);
 
@@ -184,12 +177,12 @@ int session_save(Session *s) {
 
         fprintf(f,
                 "# This is private data. Do not parse.\n"
-                "UID=%lu\n"
+                "UID="UID_FMT"\n"
                 "USER=%s\n"
                 "ACTIVE=%i\n"
                 "STATE=%s\n"
                 "REMOTE=%i\n",
-                (unsigned long) s->user->uid,
+                s->user->uid,
                 s->user->name,
                 session_is_active(s),
                 session_state_to_string(session_get_state(s)),
@@ -203,7 +196,6 @@ int session_save(Session *s) {
 
         if (s->scope)
                 fprintf(f, "SCOPE=%s\n", s->scope);
-
         if (s->scope_job)
                 fprintf(f, "SCOPE_JOB=%s\n", s->scope_job);
 
@@ -219,30 +211,73 @@ int session_save(Session *s) {
         if (s->display)
                 fprintf(f, "DISPLAY=%s\n", s->display);
 
-        if (s->remote_host)
-                fprintf(f, "REMOTE_HOST=%s\n", s->remote_host);
+        if (s->remote_host) {
+                _cleanup_free_ char *escaped;
+
+                escaped = cescape(s->remote_host);
+                if (!escaped) {
+                        r = -ENOMEM;
+                        goto finish;
+                }
+
+                fprintf(f, "REMOTE_HOST=%s\n", escaped);
+        }
+
+        if (s->remote_user) {
+                _cleanup_free_ char *escaped;
+
+                escaped = cescape(s->remote_user);
+                if (!escaped) {
+                        r = -ENOMEM;
+                        goto finish;
+                }
+
+                fprintf(f, "REMOTE_USER=%s\n", escaped);
+        }
+
+        if (s->service) {
+                _cleanup_free_ char *escaped;
 
-        if (s->remote_user)
-                fprintf(f, "REMOTE_USER=%s\n", s->remote_user);
+                escaped = cescape(s->service);
+                if (!escaped) {
+                        r = -ENOMEM;
+                        goto finish;
+                }
+
+                fprintf(f, "SERVICE=%s\n", escaped);
+        }
 
-        if (s->service)
-                fprintf(f, "SERVICE=%s\n", s->service);
+        if (s->desktop) {
+                _cleanup_free_ char *escaped;
+
+
+                escaped = cescape(s->desktop);
+                if (!escaped) {
+                        r = -ENOMEM;
+                        goto finish;
+                }
+
+                fprintf(f, "DESKTOP=%s\n", escaped);
+        }
 
         if (s->seat && seat_has_vts(s->seat))
                 fprintf(f, "VTNR=%u\n", s->vtnr);
 
+        if (!s->vtnr)
+                fprintf(f, "POSITION=%u\n", s->position);
+
         if (s->leader > 0)
-                fprintf(f, "LEADER=%lu\n", (unsigned long) s->leader);
+                fprintf(f, "LEADER="PID_FMT"\n", s->leader);
 
         if (s->audit_id > 0)
                 fprintf(f, "AUDIT=%"PRIu32"\n", s->audit_id);
 
         if (dual_timestamp_is_set(&s->timestamp))
                 fprintf(f,
-                        "REALTIME=%llu\n"
-                        "MONOTONIC=%llu\n",
-                        (unsigned long long) s->timestamp.realtime,
-                        (unsigned long long) s->timestamp.monotonic);
+                        "REALTIME="USEC_FMT"\n"
+                        "MONOTONIC="USEC_FMT"\n",
+                        s->timestamp.realtime,
+                        s->timestamp.monotonic);
 
         if (s->controller)
                 fprintf(f, "CONTROLLER=%s\n", s->controller);
@@ -257,7 +292,7 @@ int session_save(Session *s) {
 
 finish:
         if (r < 0)
-                log_error("Failed to save session data for %s: %s", s->id, strerror(-r));
+                log_error_errno(r, "Failed to save session data %s: %m", s->state_file);
 
         return r;
 }
@@ -266,6 +301,8 @@ int session_load(Session *s) {
         _cleanup_free_ char *remote = NULL,
                 *seat = NULL,
                 *vtnr = NULL,
+                *state = NULL,
+                *position = NULL,
                 *leader = NULL,
                 *type = NULL,
                 *class = NULL,
@@ -289,7 +326,10 @@ int session_load(Session *s) {
                            "REMOTE_HOST",    &s->remote_host,
                            "REMOTE_USER",    &s->remote_user,
                            "SERVICE",        &s->service,
+                           "DESKTOP",        &s->desktop,
                            "VTNR",           &vtnr,
+                           "STATE",          &state,
+                           "POSITION",       &position,
                            "LEADER",         &leader,
                            "TYPE",           &type,
                            "CLASS",          &class,
@@ -299,10 +339,8 @@ int session_load(Session *s) {
                            "CONTROLLER",     &controller,
                            NULL);
 
-        if (r < 0) {
-                log_error("Failed to read %s: %s", s->state_file, strerror(-r));
-                return r;
-        }
+        if (r < 0)
+                return log_error_errno(r, "Failed to read %s: %m", s->state_file);
 
         if (!s->user) {
                 uid_t u;
@@ -319,7 +357,7 @@ int session_load(Session *s) {
                         return r;
                 }
 
-                user = hashmap_get(s->manager->users, ULONG_TO_PTR((unsigned long) u));
+                user = hashmap_get(s->manager->users, UID_TO_PTR(u));
                 if (!user) {
                         log_error("User of session %s not known.", s->id);
                         return -ENOENT;
@@ -350,6 +388,13 @@ int session_load(Session *s) {
         if (!s->seat || !seat_has_vts(s->seat))
                 s->vtnr = 0;
 
+        if (position && s->seat) {
+                unsigned int npos;
+
+                safe_atou(position, &npos);
+                seat_claim_position(s->seat, s, npos);
+        }
+
         if (leader) {
                 k = parse_pid(leader, &s->leader);
                 if (k >= 0)
@@ -372,17 +417,21 @@ int session_load(Session *s) {
                         s->class = c;
         }
 
+        if (state && streq(state, "closing"))
+                s->stopping = true;
+
         if (s->fifo_path) {
                 int fd;
 
                 /* If we open an unopened pipe for reading we will not
                    get an EOF. to trigger an EOF we hence open it for
-                   reading, but close it right-away which then will
-                   trigger the EOF. */
+                   writing, but close it right away which then will
+                   trigger the EOF. This will happen immediately if no
+                   other process has the FIFO open for writing, i. e.
+                   when the session died before logind (re)started. */
 
                 fd = session_create_fifo(s);
-                if (fd >= 0)
-                        close_nointr_nofail(fd);
+                safe_close(fd);
         }
 
         if (realtime) {
@@ -414,7 +463,7 @@ int session_activate(Session *s) {
         assert(s->user);
 
         if (!s->seat)
-                return -ENOTSUP;
+                return -EOPNOTSUPP;
 
         if (s->seat->active == s)
                 return 0;
@@ -422,7 +471,7 @@ int session_activate(Session *s) {
         /* on seats with VTs, we let VTs manage session-switching */
         if (seat_has_vts(s->seat)) {
                 if (!s->vtnr)
-                        return -ENOTSUP;
+                        return -EOPNOTSUPP;
 
                 return chvt(s->vtnr);
         }
@@ -444,72 +493,6 @@ int session_activate(Session *s) {
         return 0;
 }
 
-static int session_link_x11_socket(Session *s) {
-        _cleanup_free_ char *t = NULL, *f = NULL;
-        char *c;
-        size_t k;
-
-        assert(s);
-        assert(s->user);
-        assert(s->user->runtime_path);
-
-        if (s->user->display)
-                return 0;
-
-        if (!s->display || !display_is_local(s->display))
-                return 0;
-
-        k = strspn(s->display+1, "0123456789");
-        f = new(char, sizeof("/tmp/.X11-unix/X") + k);
-        if (!f)
-                return log_oom();
-
-        c = stpcpy(f, "/tmp/.X11-unix/X");
-        memcpy(c, s->display+1, k);
-        c[k] = 0;
-
-        if (access(f, F_OK) < 0) {
-                log_warning("Session %s has display %s with non-existing socket %s.", s->id, s->display, f);
-                return -ENOENT;
-        }
-
-        /* Note that this cannot be in a subdir to avoid
-         * vulnerabilities since we are privileged but the runtime
-         * path is owned by the user */
-
-        t = strappend(s->user->runtime_path, "/X11-display");
-        if (!t)
-                return log_oom();
-
-        if (link(f, t) < 0) {
-                if (errno == EEXIST) {
-                        unlink(t);
-
-                        if (link(f, t) >= 0)
-                                goto done;
-                }
-
-                if (symlink(f, t) < 0) {
-
-                        if (errno == EEXIST) {
-                                unlink(t);
-
-                                if (symlink(f, t) >= 0)
-                                        goto done;
-                        }
-
-                        log_error("Failed to link %s to %s: %m", f, t);
-                        return -errno;
-                }
-        }
-
-done:
-        log_info("Linked %s to %s.", f, t);
-        s->user->display = s;
-
-        return 0;
-}
-
 static int session_start_scope(Session *s) {
         int r;
 
@@ -520,8 +503,7 @@ static int session_start_scope(Session *s) {
         if (!s->scope) {
                 _cleanup_bus_error_free_ sd_bus_error error = SD_BUS_ERROR_NULL;
                 _cleanup_free_ char *description = NULL;
-                const char *kill_mode;
-                char *scope, *job;
+                char *scope, *job = NULL;
 
                 description = strjoin("Session ", s->id, " of user ", s->user->name, NULL);
                 if (!description)
@@ -531,9 +513,7 @@ static int session_start_scope(Session *s) {
                 if (!scope)
                         return log_oom();
 
-                kill_mode = manager_shall_kill(s->manager, s->user->name) ? "control-group" : "none";
-
-                r = manager_start_scope(s->manager, scope, s->leader, s->user->slice, description, "systemd-user-sessions.service", kill_mode, &error, &job);
+                r = manager_start_scope(s->manager, scope, s->leader, s->user->slice, description, "systemd-logind.service", "systemd-user-sessions.service", &error, &job);
                 if (r < 0) {
                         log_error("Failed to start session scope %s: %s %s",
                                   scope, bus_error_message(&error, r), error.name);
@@ -573,17 +553,14 @@ int session_start(Session *s) {
         if (r < 0)
                 return r;
 
-        log_struct(s->type == SESSION_TTY || s->type == SESSION_X11 ? LOG_INFO : LOG_DEBUG,
-                   MESSAGE_ID(SD_MESSAGE_SESSION_START),
+        log_struct(s->class == SESSION_BACKGROUND ? LOG_DEBUG : LOG_INFO,
+                   LOG_MESSAGE_ID(SD_MESSAGE_SESSION_START),
                    "SESSION_ID=%s", s->id,
                    "USER_ID=%s", s->user->name,
-                   "LEADER=%lu", (unsigned long) s->leader,
-                   "MESSAGE=New session %s of user %s.", s->id, s->user->name,
+                   "LEADER="PID_FMT, s->leader,
+                   LOG_MESSAGE("New session %s of user %s.", s->id, s->user->name),
                    NULL);
 
-        /* Create X11 symlink */
-        session_link_x11_socket(s);
-
         if (!dual_timestamp_is_set(&s->timestamp))
                 dual_timestamp_get(&s->timestamp);
 
@@ -592,29 +569,30 @@ int session_start(Session *s) {
 
         s->started = true;
 
-        /* Save session data */
+        user_elect_display(s->user);
+
+        /* Save data */
         session_save(s);
         user_save(s->user);
+        if (s->seat)
+                seat_save(s->seat);
 
+        /* Send signals */
         session_send_signal(s, true);
-
+        user_send_changed(s->user, "Sessions", "Display", NULL);
         if (s->seat) {
-                seat_save(s->seat);
-
                 if (s->seat->active == s)
                         seat_send_changed(s->seat, "Sessions", "ActiveSession", NULL);
                 else
                         seat_send_changed(s->seat, "Sessions", NULL);
         }
 
-        user_send_changed(s->user, "Sessions", NULL);
-
         return 0;
 }
 
-static int session_stop_scope(Session *s) {
+static int session_stop_scope(Session *s, bool force) {
         _cleanup_bus_error_free_ sd_bus_error error = SD_BUS_ERROR_NULL;
-        char *job;
+        char *job = NULL;
         int r;
 
         assert(s);
@@ -622,48 +600,48 @@ static int session_stop_scope(Session *s) {
         if (!s->scope)
                 return 0;
 
-        r = manager_stop_unit(s->manager, s->scope, &error, &job);
-        if (r < 0) {
-                log_error("Failed to stop session scope: %s", bus_error_message(&error, r));
-                return r;
-        }
+        if (force || manager_shall_kill(s->manager, s->user->name)) {
+                r = manager_stop_unit(s->manager, s->scope, &error, &job);
+                if (r < 0) {
+                        log_error("Failed to stop session scope: %s", bus_error_message(&error, r));
+                        return r;
+                }
 
-        free(s->scope_job);
-        s->scope_job = job;
+                free(s->scope_job);
+                s->scope_job = job;
+        } else {
+                r = manager_abandon_scope(s->manager, s->scope, &error);
+                if (r < 0) {
+                        log_error("Failed to abandon session scope: %s", bus_error_message(&error, r));
+                        return r;
+                }
+        }
 
         return 0;
 }
 
-static int session_unlink_x11_socket(Session *s) {
-        _cleanup_free_ char *t = NULL;
+int session_stop(Session *s, bool force) {
         int r;
 
         assert(s);
-        assert(s->user);
-
-        if (s->user->display != s)
-                return 0;
 
-        s->user->display = NULL;
+        if (!s->user)
+                return -ESTALE;
 
-        t = strappend(s->user->runtime_path, "/X11-display");
-        if (!t)
-                return log_oom();
+        s->timer_event_source = sd_event_source_unref(s->timer_event_source);
 
-        r = unlink(t);
-        return r < 0 ? -errno : 0;
-}
+        if (s->seat)
+                seat_evict_position(s->seat, s);
 
-int session_stop(Session *s) {
-        int r;
+        /* We are going down, don't care about FIFOs anymore */
+        session_remove_fifo(s);
 
-        assert(s);
+        /* Kill cgroup */
+        r = session_stop_scope(s, force);
 
-        if (!s->user)
-                return -ESTALE;
+        s->stopping = true;
 
-        /* Kill cgroup */
-        r = session_stop_scope(s);
+        user_elect_display(s->user);
 
         session_save(s);
         user_save(s->user);
@@ -681,21 +659,23 @@ int session_finalize(Session *s) {
                 return -ESTALE;
 
         if (s->started)
-                log_struct(s->type == SESSION_TTY || s->type == SESSION_X11 ? LOG_INFO : LOG_DEBUG,
-                           MESSAGE_ID(SD_MESSAGE_SESSION_STOP),
+                log_struct(s->class == SESSION_BACKGROUND ? LOG_DEBUG : LOG_INFO,
+                           LOG_MESSAGE_ID(SD_MESSAGE_SESSION_STOP),
                            "SESSION_ID=%s", s->id,
                            "USER_ID=%s", s->user->name,
-                           "LEADER=%lu", (unsigned long) s->leader,
-                           "MESSAGE=Removed session %s.", s->id,
+                           "LEADER="PID_FMT, s->leader,
+                           LOG_MESSAGE("Removed session %s.", s->id),
                            NULL);
 
+        s->timer_event_source = sd_event_source_unref(s->timer_event_source);
+
+        if (s->seat)
+                seat_evict_position(s->seat, s);
+
         /* Kill session devices */
         while ((sd = hashmap_first(s->devices)))
                 session_device_free(sd);
 
-        /* Remove X11 symlink */
-        session_unlink_x11_socket(s);
-
         unlink(s->state_file);
         session_add_to_gc_queue(s);
         user_add_to_gc_queue(s->user);
@@ -709,16 +689,42 @@ int session_finalize(Session *s) {
                 if (s->seat->active == s)
                         seat_set_active(s->seat, NULL);
 
-                seat_send_changed(s->seat, "Sessions", NULL);
                 seat_save(s->seat);
+                seat_send_changed(s->seat, "Sessions", NULL);
         }
 
-        user_send_changed(s->user, "Sessions", NULL);
         user_save(s->user);
+        user_send_changed(s->user, "Sessions", "Display", NULL);
 
         return r;
 }
 
+static int release_timeout_callback(sd_event_source *es, uint64_t usec, void *userdata) {
+        Session *s = userdata;
+
+        assert(es);
+        assert(s);
+
+        session_stop(s, false);
+        return 0;
+}
+
+int session_release(Session *s) {
+        assert(s);
+
+        if (!s->started || s->stopping)
+                return 0;
+
+        if (s->timer_event_source)
+                return 0;
+
+        return sd_event_add_time(s->manager->event,
+                                 &s->timer_event_source,
+                                 CLOCK_MONOTONIC,
+                                 now(CLOCK_MONOTONIC) + RELEASE_USEC, 0,
+                                 release_timeout_callback, s);
+}
+
 bool session_is_active(Session *s) {
         assert(s);
 
@@ -845,7 +851,7 @@ static int session_dispatch_fifo(sd_event_source *es, int fd, uint32_t revents,
         /* EOF on the FIFO means the session died abnormally. */
 
         session_remove_fifo(s);
-        session_stop(s);
+        session_stop(s, false);
 
         return 1;
 }
@@ -877,7 +883,7 @@ int session_create_fifo(Session *s) {
         }
 
         if (!s->fifo_event_source) {
-                r = sd_event_add_io(s->manager->event, s->fifo_fd, 0, session_dispatch_fifo, s, &s->fifo_event_source);
+                r = sd_event_add_io(s->manager->event, &s->fifo_event_source, s->fifo_fd, 0, session_dispatch_fifo, s);
                 if (r < 0)
                         return r;
 
@@ -894,16 +900,11 @@ int session_create_fifo(Session *s) {
         return r;
 }
 
-void session_remove_fifo(Session *s) {
+static void session_remove_fifo(Session *s) {
         assert(s);
 
-        if (s->fifo_event_source)
-                s->fifo_event_source = sd_event_source_unref(s->fifo_event_source);
-
-        if (s->fifo_fd >= 0) {
-                close_nointr_nofail(s->fifo_fd);
-                s->fifo_fd = -1;
-        }
+        s->fifo_event_source = sd_event_source_unref(s->fifo_event_source);
+        s->fifo_fd = safe_close(s->fifo_fd);
 
         if (s->fifo_path) {
                 unlink(s->fifo_path);
@@ -913,8 +914,6 @@ void session_remove_fifo(Session *s) {
 }
 
 bool session_check_gc(Session *s, bool drop_not_started) {
-        int r;
-
         assert(s);
 
         if (drop_not_started && !s->started)
@@ -924,11 +923,7 @@ bool session_check_gc(Session *s, bool drop_not_started) {
                 return false;
 
         if (s->fifo_fd >= 0) {
-                r = pipe_eof(s->fifo_fd);
-                if (r < 0)
-                        return true;
-
-                if (r == 0)
+                if (pipe_eof(s->fifo_fd) <= 0)
                         return true;
         }
 
@@ -954,12 +949,13 @@ void session_add_to_gc_queue(Session *s) {
 SessionState session_get_state(Session *s) {
         assert(s);
 
-        if (s->scope_job)
-                return SESSION_OPENING;
-
-        if (s->fifo_fd < 0)
+        /* always check closing first */
+        if (s->stopping || s->timer_event_source)
                 return SESSION_CLOSING;
 
+        if (s->scope_job || s->fifo_fd < 0)
+                return SESSION_OPENING;
+
         if (session_is_active(s))
                 return SESSION_ACTIVE;
 
@@ -976,98 +972,132 @@ int session_kill(Session *s, KillWho who, int signo) {
 }
 
 static int session_open_vt(Session *s) {
-        char path[128];
+        char path[sizeof("/dev/tty") + DECIMAL_STR_MAX(s->vtnr)];
 
-        if (!s->vtnr)
-                return -1;
+        if (s->vtnr < 1)
+                return -ENODEV;
 
         if (s->vtfd >= 0)
                 return s->vtfd;
 
         sprintf(path, "/dev/tty%u", s->vtnr);
-        s->vtfd = open(path, O_RDWR | O_CLOEXEC | O_NONBLOCK | O_NOCTTY);
-        if (s->vtfd < 0) {
-                log_error("cannot open VT %s of session %s: %m", path, s->id);
-                return -1;
-        }
+        s->vtfd = open_terminal(path, O_RDWR | O_CLOEXEC | O_NONBLOCK | O_NOCTTY);
+        if (s->vtfd < 0)
+                return log_error_errno(errno, "cannot open VT %s of session %s: %m", path, s->id);
 
         return s->vtfd;
 }
 
-static int session_vt_fn(sd_event_source *source, const struct signalfd_siginfo *si, void *data) {
-        Session *s = data;
-
-        if (s->vtfd >= 0)
-                ioctl(s->vtfd, VT_RELDISP, 1);
-
-        return 0;
-}
-
-void session_mute_vt(Session *s) {
+int session_prepare_vt(Session *s) {
         int vt, r;
         struct vt_mode mode = { 0 };
-        sigset_t mask;
+
+        if (s->vtnr < 1)
+                return 0;
 
         vt = session_open_vt(s);
         if (vt < 0)
-                return;
+                return vt;
 
-        r = ioctl(vt, KDSKBMODE, K_OFF);
-        if (r < 0)
+        r = fchown(vt, s->user->uid, -1);
+        if (r < 0) {
+                r = -errno;
+                log_error_errno(errno, "Cannot change owner of /dev/tty%u: %m", s->vtnr);
                 goto error;
+        }
 
-        r = ioctl(vt, KDSETMODE, KD_GRAPHICS);
-        if (r < 0)
+        r = ioctl(vt, KDSKBMODE, K_OFF);
+        if (r < 0) {
+                r = -errno;
+                log_error_errno(errno, "Cannot set K_OFF on /dev/tty%u: %m", s->vtnr);
                 goto error;
+        }
 
-        sigemptyset(&mask);
-        sigaddset(&mask, SIGUSR1);
-        sigprocmask(SIG_BLOCK, &mask, NULL);
-
-        r = sd_event_add_signal(s->manager->event, SIGUSR1, session_vt_fn, s, &s->vt_source);
-        if (r < 0)
+        r = ioctl(vt, KDSETMODE, KD_GRAPHICS);
+        if (r < 0) {
+                r = -errno;
+                log_error_errno(errno, "Cannot set KD_GRAPHICS on /dev/tty%u: %m", s->vtnr);
                 goto error;
+        }
 
         /* Oh, thanks to the VT layer, VT_AUTO does not work with KD_GRAPHICS.
          * So we need a dummy handler here which just acknowledges *all* VT
          * switch requests. */
         mode.mode = VT_PROCESS;
-        mode.relsig = SIGUSR1;
-        mode.acqsig = SIGUSR1;
+        mode.relsig = SIGRTMIN;
+        mode.acqsig = SIGRTMIN + 1;
         r = ioctl(vt, VT_SETMODE, &mode);
-        if (r < 0)
+        if (r < 0) {
+                r = -errno;
+                log_error_errno(errno, "Cannot set VT_PROCESS on /dev/tty%u: %m", s->vtnr);
                 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) {
-        _cleanup_free_ char *utf8;
+        _cleanup_free_ char *utf8 = NULL;
         int vt, kb = K_XLATE;
         struct vt_mode mode = { 0 };
 
+        /* We need to get a fresh handle to the virtual terminal,
+         * since the old file-descriptor is potentially in a hung-up
+         * state after the controlling process exited; we do a
+         * little dance to avoid having the terminal be available
+         * for reuse before we've cleaned it up.
+         */
+        int old_fd = s->vtfd;
+        s->vtfd = -1;
+
         vt = session_open_vt(s);
+        safe_close(old_fd);
+
         if (vt < 0)
                 return;
 
-        sd_event_source_unref(s->vt_source);
-        s->vt_source = NULL;
-
-        ioctl(vt, KDSETMODE, KD_TEXT);
+        (void) ioctl(vt, KDSETMODE, KD_TEXT);
 
         if (read_one_line_file("/sys/module/vt/parameters/default_utf8", &utf8) >= 0 && *utf8 == '1')
                 kb = K_UNICODE;
-        ioctl(vt, KDSKBMODE, kb);
+
+        (void) ioctl(vt, KDSKBMODE, kb);
 
         mode.mode = VT_AUTO;
-        ioctl(vt, VT_SETMODE, &mode);
+        (void) ioctl(vt, VT_SETMODE, &mode);
 
-        close_nointr_nofail(vt);
-        s->vtfd = -1;
+        fchown(vt, 0, -1);
+
+        s->vtfd = safe_close(s->vtfd);
+}
+
+void session_leave_vt(Session *s) {
+        int r;
+
+        assert(s);
+
+        /* This is called whenever we get a VT-switch signal from the kernel.
+         * We acknowledge all of them unconditionally. Note that session are
+         * free to overwrite those handlers and we only register them for
+         * sessions with controllers. Legacy sessions are not affected.
+         * However, if we switch from a non-legacy to a legacy session, we must
+         * make sure to pause all device before acknowledging the switch. We
+         * process the real switch only after we are notified via sysfs, so the
+         * legacy session might have already started using the devices. If we
+         * don't pause the devices before the switch, we might confuse the
+         * session we switch to. */
+
+        if (s->vtfd < 0)
+                return;
+
+        session_device_pause_all(s);
+        r = ioctl(s->vtfd, VT_RELDISP, 1);
+        if (r < 0)
+                log_debug_errno(errno, "Cannot release VT of session %s: %m", s->id);
 }
 
 bool session_is_controller(Session *s, const char *sender) {
@@ -1076,30 +1106,30 @@ bool session_is_controller(Session *s, const char *sender) {
         return streq_ptr(s->controller, sender);
 }
 
-static void session_swap_controller(Session *s, char *name) {
+static void session_release_controller(Session *s, bool notify) {
+        _cleanup_free_ char *name = NULL;
         SessionDevice *sd;
 
-        if (s->controller) {
-                manager_drop_busname(s->manager, s->controller);
-                free(s->controller);
-                s->controller = NULL;
+        if (!s->controller)
+                return;
 
-                /* Drop all devices as they're now unused. Do that after the
-                 * controller is released to avoid sending out useles
-                 * dbus signals. */
-                while ((sd = hashmap_first(s->devices)))
-                        session_device_free(sd);
+        name = s->controller;
 
-                if (!name)
-                        session_restore_vt(s);
-        }
+        /* By resetting the controller before releasing the devices, we won't
+         * send notification signals. This avoids sending useless notifications
+         * if the controller is released on disconnects. */
+        if (!notify)
+                s->controller = NULL;
 
-        s->controller = name;
-        session_save(s);
+        while ((sd = hashmap_first(s->devices)))
+                session_device_free(sd);
+
+        s->controller = NULL;
+        manager_drop_busname(s->manager, name);
 }
 
 int session_set_controller(Session *s, const char *sender, bool force) {
-        char *t;
+        _cleanup_free_ char *name = NULL;
         int r;
 
         assert(s);
@@ -1110,17 +1140,13 @@ int session_set_controller(Session *s, const char *sender, bool force) {
         if (s->controller && !force)
                 return -EBUSY;
 
-        t = strdup(sender);
-        if (!t)
+        name = strdup(sender);
+        if (!name)
                 return -ENOMEM;
 
-        r = manager_watch_busname(s->manager, sender);
-        if (r) {
-                free(t);
+        r = manager_watch_busname(s->manager, name);
+        if (r)
                 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
@@ -1130,7 +1156,16 @@ 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_mute_vt(s);
+        r = session_prepare_vt(s);
+        if (r < 0) {
+                manager_drop_busname(s->manager, name);
+                return r;
+        }
+
+        session_release_controller(s, true);
+        s->controller = name;
+        name = NULL;
+        session_save(s);
 
         return 0;
 }
@@ -1141,7 +1176,9 @@ void session_drop_controller(Session *s) {
         if (!s->controller)
                 return;
 
-        session_swap_controller(s, NULL);
+        session_release_controller(s, false);
+        session_save(s);
+        session_restore_vt(s);
 }
 
 static const char* const session_state_table[_SESSION_STATE_MAX] = {
@@ -1154,9 +1191,12 @@ static const char* const session_state_table[_SESSION_STATE_MAX] = {
 DEFINE_STRING_TABLE_LOOKUP(session_state, SessionState);
 
 static const char* const session_type_table[_SESSION_TYPE_MAX] = {
+        [SESSION_UNSPECIFIED] = "unspecified",
         [SESSION_TTY] = "tty",
         [SESSION_X11] = "x11",
-        [SESSION_UNSPECIFIED] = "unspecified"
+        [SESSION_WAYLAND] = "wayland",
+        [SESSION_MIR] = "mir",
+        [SESSION_WEB] = "web",
 };
 
 DEFINE_STRING_TABLE_LOOKUP(session_type, SessionType);