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.

1 files changed, 7 insertions, 7 deletions

diff --git a/src/home/homed-home.c b/src/home/homed-home.c
index f1db828ed0..5a777e88ef 100644
--- a/src/home/homed-home.c
+++ b/src/home/homed-home.c
@@ -188,17 +188,17 @@ 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);
 
@@ -888,7 +888,7 @@ 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));
@@ -1067,7 +1067,7 @@ 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;
         }