homed: disable event sources before unreffing them

C.f. 9793530228.

We'd crash when trying to access an already-deallocated object:

Thread no. 1 (7 frames)
 #2 log_assert_failed_realm at ../src/basic/log.c:844
 #3 event_inotify_data_drop at ../src/libsystemd/sd-event/sd-event.c:3035
 #4 source_dispatch at ../src/libsystemd/sd-event/sd-event.c:3250
 #5 sd_event_dispatch at ../src/libsystemd/sd-event/sd-event.c:3631
 #6 sd_event_run at ../src/libsystemd/sd-event/sd-event.c:3689
 #7 sd_event_loop at ../src/libsystemd/sd-event/sd-event.c:3711
 #8 run at ../src/home/homed.c:47

The source in question is an inotify source, and the messages are:

systemd-homed[1340]: /home/ moved or renamed, recreating watch and rescanning.
systemd-homed[1340]: Assertion '*_head == _item' failed at src/libsystemd/sd-event/sd-event.c:3035, function event_inotify_data_drop(). Aborting.

on_home_inotify() got called, then manager_watch_home(), which unrefs the
existing inotify_event_source. I assume that the source gets dispatched again
because it was still in the pending queue.

I can't reproduce the issue (timing?), but this should
fix #17824, https://bugzilla.redhat.com/show_bug.cgi?id=1899264.

(cherry picked from commit cf5366387b24633284ee92285ea64a282270d591)
(cherry picked from commit 668554d9dbfa9f240dd18455a52c68f3f48bdb81)

4 files changed, 12 insertions, 12 deletions

diff --git a/src/home/homed-home-bus.c b/src/home/homed-home-bus.c
index 6be361a5aa..bc133a51e4 100644
--- a/src/home/homed-home-bus.c
+++ b/src/home/homed-home-bus.c
@@ -885,7 +885,7 @@ static int on_deferred_change(sd_event_source *s, void *userdata) {
 
         assert(h);
 
-        h->deferred_change_event_source = sd_event_source_unref(h->deferred_change_event_source);
+        h->deferred_change_event_source = sd_event_source_disable_unref(h->deferred_change_event_source);
 
         r = bus_home_path(h, &path);
         if (r < 0) {
diff --git a/src/home/homed-home.c b/src/home/homed-home.c
index c5dfe3d2f2..28c8e701c4 100644
--- a/src/home/homed-home.c
+++ b/src/home/homed-home.c
@@ -187,17 +187,17 @@ Home *home_free(Home *h) {
         user_record_unref(h->record);
         user_record_unref(h->secret);
 
-        h->worker_event_source = sd_event_source_unref(h->worker_event_source);
+        h->worker_event_source = sd_event_source_disable_unref(h->worker_event_source);
         safe_close(h->worker_stdout_fd);
         free(h->user_name);
         free(h->sysfs);
 
-        h->ref_event_source_please_suspend = sd_event_source_unref(h->ref_event_source_please_suspend);
-        h->ref_event_source_dont_suspend = sd_event_source_unref(h->ref_event_source_dont_suspend);
+        h->ref_event_source_please_suspend = sd_event_source_disable_unref(h->ref_event_source_please_suspend);
+        h->ref_event_source_dont_suspend = sd_event_source_disable_unref(h->ref_event_source_dont_suspend);
 
         h->pending_operations = ordered_set_free(h->pending_operations);
-        h->pending_event_source = sd_event_source_unref(h->pending_event_source);
-        h->deferred_change_event_source = sd_event_source_unref(h->deferred_change_event_source);
+        h->pending_event_source = sd_event_source_disable_unref(h->pending_event_source);
+        h->deferred_change_event_source = sd_event_source_disable_unref(h->deferred_change_event_source);
 
         h->current_operation = operation_unref(h->current_operation);
 
@@ -885,7 +885,7 @@ static int home_on_worker_process(sd_event_source *s, const siginfo_t *si, void
         (void) hashmap_remove_value(h->manager->homes_by_worker_pid, PID_TO_PTR(h->worker_pid), h);
 
         h->worker_pid = 0;
-        h->worker_event_source = sd_event_source_unref(h->worker_event_source);
+        h->worker_event_source = sd_event_source_disable_unref(h->worker_event_source);
 
         if (si->si_code != CLD_EXITED) {
                 assert(IN_SET(si->si_code, CLD_KILLED, CLD_DUMPED));
@@ -1054,7 +1054,7 @@ static int home_start_work(Home *h, const char *verb, UserRecord *hr, UserRecord
 
         r = hashmap_put(h->manager->homes_by_worker_pid, PID_TO_PTR(pid), h);
         if (r < 0) {
-                h->worker_event_source = sd_event_source_unref(h->worker_event_source);
+                h->worker_event_source = sd_event_source_disable_unref(h->worker_event_source);
                 return r;
         }
 
diff --git a/src/home/homed-manager-bus.c b/src/home/homed-manager-bus.c
index ce6919a1a7..4c0158d901 100644
--- a/src/home/homed-manager-bus.c
+++ b/src/home/homed-manager-bus.c
@@ -824,7 +824,7 @@ static int on_deferred_auto_login(sd_event_source *s, void *userdata) {
 
         assert(m);
 
-        m->deferred_auto_login_event_source = sd_event_source_unref(m->deferred_auto_login_event_source);
+        m->deferred_auto_login_event_source = sd_event_source_disable_unref(m->deferred_auto_login_event_source);
 
         r = sd_bus_emit_properties_changed(
                         m->bus,
diff --git a/src/home/homed-manager.c b/src/home/homed-manager.c
index 3b75e2c345..2024ff24ff 100644
--- a/src/home/homed-manager.c
+++ b/src/home/homed-manager.c
@@ -79,7 +79,7 @@ static void manager_watch_home(Manager *m) {
 
         assert(m);
 
-        m->inotify_event_source = sd_event_source_unref(m->inotify_event_source);
+        m->inotify_event_source = sd_event_source_disable_unref(m->inotify_event_source);
         m->scan_slash_home = false;
 
         if (statfs("/home/", &sfs) < 0) {
@@ -1636,7 +1636,7 @@ static int on_deferred_rescan(sd_event_source *s, void *userdata) {
 
         assert(m);
 
-        m->deferred_rescan_event_source = sd_event_source_unref(m->deferred_rescan_event_source);
+        m->deferred_rescan_event_source = sd_event_source_disable_unref(m->deferred_rescan_event_source);
 
         manager_enumerate_devices(m);
         manager_enumerate_images(m);
@@ -1674,7 +1674,7 @@ static int on_deferred_gc(sd_event_source *s, void *userdata) {
 
         assert(m);
 
-        m->deferred_gc_event_source = sd_event_source_unref(m->deferred_gc_event_source);
+        m->deferred_gc_event_source = sd_event_source_disable_unref(m->deferred_gc_event_source);
 
         manager_gc_images(m);
         return 0;