From 8f1df942e2237124f7559176081af7ac631d3422 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Zbigniew=20J=C4=99drzejewski-Szmek?= <zbyszek@in.waw.pl>
Date: Tue, 13 Feb 2018 23:57:43 +0100
Subject: [PATCH] pid1: properly remove references to the unit from gc queue
 during final cleanup

When various references to the unit were dropped during cleanup in unit_free(),
add_to_gc_queue() could be called on this unit. If the unit was previously in
the gc queue (at the time when unit_free() was called on it), this wouldn't
matter, because it'd have in_gc_queue still set even though it was already
removed from the queue. But if it wasn't set, then the unit could be added to
the queue. Then after unit_free() would deallocate the unit, we would be left
with a dangling pointer in gc_queue.

A unit could be added to the gc queue in two places called from unit_free():
in the job_install calls, and in unit_ref_unset(). The first was OK, because
it was above the LIST_REMOVE(gc_queue,...) call, but the second was not, because
it was after that. Move the all LIST_REMOVE() calls down.

(cherry picked from commit 1bdf2790025e661e41894129eb390bb032b88585)

Related: #1718953
---
 src/core/unit.c | 34 +++++++++++++++++-----------------
 1 file changed, 17 insertions(+), 17 deletions(-)

diff --git a/src/core/unit.c b/src/core/unit.c
index 63f00acc0a..def36a0930 100644
--- a/src/core/unit.c
+++ b/src/core/unit.c
@@ -506,23 +506,6 @@ void unit_free(Unit *u) {
         for (d = 0; d < _UNIT_DEPENDENCY_MAX; d++)
                 bidi_set_free(u, u->dependencies[d]);
 
-        if (u->type != _UNIT_TYPE_INVALID)
-                LIST_REMOVE(units_by_type, u->manager->units_by_type[u->type], u);
-
-        if (u->in_load_queue)
-                LIST_REMOVE(load_queue, u->manager->load_queue, u);
-
-        if (u->in_dbus_queue)
-                LIST_REMOVE(dbus_queue, u->manager->dbus_unit_queue, u);
-
-        if (u->in_cleanup_queue)
-                LIST_REMOVE(cleanup_queue, u->manager->cleanup_queue, u);
-
-        if (u->in_gc_queue) {
-                LIST_REMOVE(gc_queue, u->manager->gc_queue, u);
-                u->manager->n_in_gc_queue--;
-        }
-
         if (u->in_target_deps_queue)
                 LIST_REMOVE(target_deps_queue, u->manager->target_deps_queue, u);
 
@@ -543,6 +526,23 @@ void unit_free(Unit *u) {
         while (u->refs_by_target)
                 unit_ref_unset(u->refs_by_target);
 
+        if (u->type != _UNIT_TYPE_INVALID)
+                LIST_REMOVE(units_by_type, u->manager->units_by_type[u->type], u);
+
+        if (u->in_load_queue)
+                LIST_REMOVE(load_queue, u->manager->load_queue, u);
+
+        if (u->in_dbus_queue)
+                LIST_REMOVE(dbus_queue, u->manager->dbus_unit_queue, u);
+
+        if (u->in_cleanup_queue)
+                LIST_REMOVE(cleanup_queue, u->manager->cleanup_queue, u);
+
+        if (u->in_gc_queue) {
+                LIST_REMOVE(gc_queue, u->manager->gc_queue, u);
+                u->manager->n_in_gc_queue--;
+        }
+
         condition_free_list(u->conditions);
         condition_free_list(u->asserts);