core: don't choke if a unit another unit triggers vanishes during reload

Fixes: #1981

3 files changed, 62 insertions, 9 deletions

diff --git a/src/core/automount.c b/src/core/automount.c
index 772ec222ca..5dc6fd98e7 100644
--- a/src/core/automount.c
+++ b/src/core/automount.c
@@ -726,7 +726,15 @@ static void automount_enter_runnning(Automount *a) {
         if (!S_ISDIR(st.st_mode) || st.st_dev != a->dev_id)
                 log_unit_info(UNIT(a), "Automount point already active?");
         else {
-                r = manager_add_job(UNIT(a)->manager, JOB_START, UNIT_TRIGGER(UNIT(a)), JOB_REPLACE, &error, NULL);
+                Unit *trigger;
+
+                trigger = UNIT_TRIGGER(UNIT(a));
+                if (!trigger) {
+                        log_unit_error(UNIT(a), "Unit to trigger vanished.");
+                        goto fail;
+                }
+
+                r = manager_add_job(UNIT(a)->manager, JOB_START, trigger, JOB_REPLACE, &error, NULL);
                 if (r < 0) {
                         log_unit_warning(UNIT(a), "Failed to queue mount startup job: %s", bus_error_message(&error, r));
                         goto fail;
@@ -742,6 +750,7 @@ fail:
 
 static int automount_start(Unit *u) {
         Automount *a = AUTOMOUNT(u);
+        Unit *trigger;
 
         assert(a);
         assert(a->state == AUTOMOUNT_DEAD || a->state == AUTOMOUNT_FAILED);
@@ -751,8 +760,11 @@ static int automount_start(Unit *u) {
                 return -EEXIST;
         }
 
-        if (UNIT_TRIGGER(u)->load_state != UNIT_LOADED)
+        trigger = UNIT_TRIGGER(u);
+        if (!trigger || trigger->load_state != UNIT_LOADED) {
+                log_unit_error(u, "Refusing to start, unit to trigger not loaded.");
                 return -ENOENT;
+        }
 
         a->result = AUTOMOUNT_SUCCESS;
         automount_enter_waiting(a);
@@ -899,6 +911,7 @@ static int automount_dispatch_io(sd_event_source *s, int fd, uint32_t events, vo
         union autofs_v5_packet_union packet;
         Automount *a = AUTOMOUNT(userdata);
         struct stat st;
+        Unit *trigger;
         int r;
 
         assert(a);
@@ -971,7 +984,13 @@ static int automount_dispatch_io(sd_event_source *s, int fd, uint32_t events, vo
                         break;
                 }
 
-                r = manager_add_job(UNIT(a)->manager, JOB_STOP, UNIT_TRIGGER(UNIT(a)), JOB_REPLACE, &error, NULL);
+                trigger = UNIT_TRIGGER(UNIT(a));
+                if (!trigger) {
+                        log_unit_error(UNIT(a), "Unit to trigger vanished.");
+                        goto fail;
+                }
+
+                r = manager_add_job(UNIT(a)->manager, JOB_STOP, trigger, JOB_REPLACE, &error, NULL);
                 if (r < 0) {
                         log_unit_warning(UNIT(a), "Failed to queue umount startup job: %s", bus_error_message(&error, r));
                         goto fail;
diff --git a/src/core/path.c b/src/core/path.c
index 610901275c..460c1d3bf2 100644
--- a/src/core/path.c
+++ b/src/core/path.c
@@ -464,6 +464,7 @@ static void path_enter_dead(Path *p, PathResult f) {
 
 static void path_enter_running(Path *p) {
         _cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
+        Unit *trigger;
         int r;
 
         assert(p);
@@ -472,7 +473,14 @@ static void path_enter_running(Path *p) {
         if (unit_stop_pending(UNIT(p)))
                 return;
 
-        r = manager_add_job(UNIT(p)->manager, JOB_START, UNIT_TRIGGER(UNIT(p)), JOB_REPLACE, &error, NULL);
+        trigger = UNIT_TRIGGER(UNIT(p));
+        if (!trigger) {
+                log_unit_error(UNIT(p), "Unit to trigger vanished.");
+                path_enter_dead(p, TIMER_FAILURE_RESOURCES);
+                return;
+        }
+
+        r = manager_add_job(UNIT(p)->manager, JOB_START, trigger, JOB_REPLACE, &error, NULL);
         if (r < 0)
                 goto fail;
 
@@ -553,12 +561,16 @@ static void path_mkdir(Path *p) {
 
 static int path_start(Unit *u) {
         Path *p = PATH(u);
+        Unit *trigger;
 
         assert(p);
         assert(p->state == PATH_DEAD || p->state == PATH_FAILED);
 
-        if (UNIT_TRIGGER(u)->load_state != UNIT_LOADED)
+        trigger = UNIT_TRIGGER(u);
+        if (!trigger || trigger->load_state != UNIT_LOADED) {
+                log_unit_error(u, "Refusing to start, unit to trigger not loaded.");
                 return -ENOENT;
+        }
 
         path_mkdir(p);
 
diff --git a/src/core/timer.c b/src/core/timer.c
index 5dd7df14d1..6f3e6a8db3 100644
--- a/src/core/timer.c
+++ b/src/core/timer.c
@@ -357,8 +357,18 @@ static void timer_enter_waiting(Timer *t, bool initial) {
         usec_t base = 0;
         bool leave_around = false;
         TimerValue *v;
+        Unit *trigger;
         int r;
 
+        assert(t);
+
+        trigger = UNIT_TRIGGER(UNIT(t));
+        if (!trigger) {
+                log_unit_error(UNIT(t), "Unit to trigger vanished.");
+                timer_enter_dead(t, TIMER_FAILURE_RESOURCES);
+                return;
+        }
+
         /* If we shall wake the system we use the boottime clock
          * rather than the monotonic clock. */
 
@@ -417,7 +427,7 @@ static void timer_enter_waiting(Timer *t, bool initial) {
 
                         case TIMER_UNIT_ACTIVE:
                                 leave_around = true;
-                                base = UNIT_TRIGGER(UNIT(t))->inactive_exit_timestamp.monotonic;
+                                base = trigger->inactive_exit_timestamp.monotonic;
 
                                 if (base <= 0)
                                         base = t->last_trigger.monotonic;
@@ -429,7 +439,7 @@ static void timer_enter_waiting(Timer *t, bool initial) {
 
                         case TIMER_UNIT_INACTIVE:
                                 leave_around = true;
-                                base = UNIT_TRIGGER(UNIT(t))->inactive_enter_timestamp.monotonic;
+                                base = trigger->inactive_enter_timestamp.monotonic;
 
                                 if (base <= 0)
                                         base = t->last_trigger.monotonic;
@@ -552,6 +562,7 @@ fail:
 
 static void timer_enter_running(Timer *t) {
         _cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
+        Unit *trigger;
         int r;
 
         assert(t);
@@ -560,7 +571,14 @@ static void timer_enter_running(Timer *t) {
         if (unit_stop_pending(UNIT(t)))
                 return;
 
-        r = manager_add_job(UNIT(t)->manager, JOB_START, UNIT_TRIGGER(UNIT(t)), JOB_REPLACE, &error, NULL);
+        trigger = UNIT_TRIGGER(UNIT(t));
+        if (!trigger) {
+                log_unit_error(UNIT(t), "Unit to trigger vanished.");
+                timer_enter_dead(t, TIMER_FAILURE_RESOURCES);
+                return;
+        }
+
+        r = manager_add_job(UNIT(t)->manager, JOB_START, trigger, JOB_REPLACE, &error, NULL);
         if (r < 0)
                 goto fail;
 
@@ -580,12 +598,16 @@ fail:
 static int timer_start(Unit *u) {
         Timer *t = TIMER(u);
         TimerValue *v;
+        Unit *trigger;
 
         assert(t);
         assert(t->state == TIMER_DEAD || t->state == TIMER_FAILED);
 
-        if (UNIT_TRIGGER(u)->load_state != UNIT_LOADED)
+        trigger = UNIT_TRIGGER(u);
+        if (!trigger || trigger->load_state != UNIT_LOADED) {
+                log_unit_error(u, "Refusing to start, unit to trigger not loaded.");
                 return -ENOENT;
+        }
 
         t->last_trigger = DUAL_TIMESTAMP_NULL;