nspawn: unref the notify event source (#4941)

Fixes:
```
sudo ./libtool --mode=execute valgrind --leak-check=full ./systemd-nspawn -D ./CONT/ -b
...
==21224== 2,444 (656 direct, 1,788 indirect) bytes in 1 blocks are definitely lost in loss record 13 of 15
==21224==    at 0x4C2FA50: calloc (vg_replace_malloc.c:711)
==21224==    by 0x4F6F565: sd_event_new (sd-event.c:431)
==21224==    by 0x1210BE: run (nspawn.c:3351)
==21224==    by 0x123908: main (nspawn.c:3826)
==21224==
==21224== LEAK SUMMARY:
==21224==    definitely lost: 656 bytes in 1 blocks
==21224==    indirectly lost: 1,788 bytes in 11 blocks
==21224==      possibly lost: 0 bytes in 0 blocks
==21224==    still reachable: 8,344 bytes in 3 blocks
==21224==         suppressed: 0 bytes in 0 blocks
```
Closes #4934

1 files changed, 5 insertions, 5 deletions

diff --git a/src/nspawn/nspawn.c b/src/nspawn/nspawn.c
index dcc639f15c..faf1ecc5df 100644
--- a/src/nspawn/nspawn.c
+++ b/src/nspawn/nspawn.c
@@ -2796,15 +2796,14 @@ static int nspawn_dispatch_notify_fd(sd_event_source *source, int fd, uint32_t r
         return 0;
 }
 
-static int setup_sd_notify_parent(sd_event *event, int fd, pid_t *inner_child_pid) {
+static int setup_sd_notify_parent(sd_event *event, int fd, pid_t *inner_child_pid, sd_event_source **notify_event_source) {
         int r;
-        sd_event_source *notify_event_source;
 
-        r = sd_event_add_io(event, &notify_event_source, fd, EPOLLIN, nspawn_dispatch_notify_fd, inner_child_pid);
+        r = sd_event_add_io(event, notify_event_source, fd, EPOLLIN, nspawn_dispatch_notify_fd, inner_child_pid);
         if (r < 0)
                 return log_error_errno(r, "Failed to allocate notify event source: %m");
 
-        (void) sd_event_source_set_description(notify_event_source, "nspawn-notify");
+        (void) sd_event_source_set_description(*notify_event_source, "nspawn-notify");
 
         return 0;
 }
@@ -3069,6 +3068,7 @@ static int run(int master,
                 uid_shift_socket_pair[2] = { -1, -1 };
         _cleanup_close_ int notify_socket= -1;
         _cleanup_(barrier_destroy) Barrier barrier = BARRIER_NULL;
+        _cleanup_(sd_event_source_unrefp) sd_event_source *notify_event_source = NULL;
         _cleanup_(sd_event_unrefp) sd_event *event = NULL;
         _cleanup_(pty_forward_freep) PTYForward *forward = NULL;
         _cleanup_(sd_netlink_unrefp) sd_netlink *rtnl = NULL;
@@ -3352,7 +3352,7 @@ static int run(int master,
         if (r < 0)
                 return log_error_errno(r, "Failed to get default event source: %m");
 
-        r = setup_sd_notify_parent(event, notify_socket, PID_TO_PTR(*pid));
+        r = setup_sd_notify_parent(event, notify_socket, PID_TO_PTR(*pid), &notify_event_source);
         if (r < 0)
                 return r;