1 files changed, 31 insertions, 2 deletions

diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c
index 57bc1fd35b3c..b3c7fd554250 100644
--- a/kernel/pid_namespace.c
+++ b/kernel/pid_namespace.c
@@ -149,7 +149,12 @@ void zap_pid_ns_processes(struct pid_namespace *pid_ns)
 {
         int nr;
         int rc;
-        struct task_struct *task;
+        struct task_struct *task, *me = current;
+
+        /* Ignore SIGCHLD causing any terminated children to autoreap */
+        spin_lock_irq(&me->sighand->siglock);
+        me->sighand->action[SIGCHLD - 1].sa.sa_handler = SIG_IGN;
+        spin_unlock_irq(&me->sighand->siglock);
 
         /*
          * The last thread in the cgroup-init thread group is terminating.
@@ -179,11 +184,31 @@ void zap_pid_ns_processes(struct pid_namespace *pid_ns)
         }
         read_unlock(&tasklist_lock);
 
+        /* Firstly reap the EXIT_ZOMBIE children we may have. */
         do {
                 clear_thread_flag(TIF_SIGPENDING);
                 rc = sys_wait4(-1, NULL, __WALL, NULL);
         } while (rc != -ECHILD);
 
+        /*
+         * sys_wait4() above can't reap the TASK_DEAD children.
+         * Make sure they all go away, see __unhash_process().
+         */
+        for (;;) {
+                bool need_wait = false;
+
+                read_lock(&tasklist_lock);
+                if (!list_empty(&current->children)) {
+                        __set_current_state(TASK_UNINTERRUPTIBLE);
+                        need_wait = true;
+                }
+                read_unlock(&tasklist_lock);
+
+                if (!need_wait)
+                        break;
+                schedule();
+        }
+
         if (pid_ns->reboot)
                 current->signal->group_exit_code = pid_ns->reboot;
 
@@ -191,6 +216,7 @@ void zap_pid_ns_processes(struct pid_namespace *pid_ns)
         return;
 }
 
+#ifdef CONFIG_CHECKPOINT_RESTORE
 static int pid_ns_ctl_handler(struct ctl_table *table, int write,
                 void __user *buffer, size_t *lenp, loff_t *ppos)
 {
@@ -218,8 +244,8 @@ static struct ctl_table pid_ns_ctl_table[] = {
         },
         { }
 };
-
 static struct ctl_path kern_path[] = { { .procname = "kernel", }, { } };
+#endif  /* CONFIG_CHECKPOINT_RESTORE */
 
 int reboot_pid_ns(struct pid_namespace *pid_ns, int cmd)
 {
@@ -253,7 +279,10 @@ int reboot_pid_ns(struct pid_namespace *pid_ns, int cmd)
 static __init int pid_namespaces_init(void)
 {
         pid_ns_cachep = KMEM_CACHE(pid_namespace, SLAB_PANIC);
+
+#ifdef CONFIG_CHECKPOINT_RESTORE
         register_sysctl_paths(kern_path, pid_ns_ctl_table);
+#endif
         return 0;
 }