1 files changed, 35 insertions, 31 deletions

diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c
index 7ade20e95232..7098ed44e717 100644
--- a/kernel/pid_namespace.c
+++ b/kernel/pid_namespace.c
@@ -70,6 +70,8 @@ static void dec_pid_namespaces(struct ucounts *ucounts)
 	dec_ucount(ucounts, UCOUNT_PID_NAMESPACES);
 }
 
+static void destroy_pid_namespace_work(struct work_struct *work);
+
 static struct pid_namespace *create_pid_namespace(struct user_namespace *user_ns,
 	struct pid_namespace *parent_pid_ns)
 {
@@ -105,17 +107,27 @@ static struct pid_namespace *create_pid_namespace(struct user_namespace *user_ns
 		goto out_free_idr;
 	ns->ns.ops = &pidns_operations;
 
+	ns->pid_max = PID_MAX_LIMIT;
+	err = register_pidns_sysctls(ns);
+	if (err)
+		goto out_free_inum;
+
 	refcount_set(&ns->ns.count, 1);
 	ns->level = level;
 	ns->parent = get_pid_ns(parent_pid_ns);
 	ns->user_ns = get_user_ns(user_ns);
 	ns->ucounts = ucounts;
 	ns->pid_allocated = PIDNS_ADDING;
+	INIT_WORK(&ns->work, destroy_pid_namespace_work);
+
 #if defined(CONFIG_SYSCTL) && defined(CONFIG_MEMFD_CREATE)
 	ns->memfd_noexec_scope = pidns_memfd_noexec_scope(parent_pid_ns);
 #endif
+
 	return ns;
 
+out_free_inum:
+	ns_free_inum(&ns->ns);
 out_free_idr:
 	idr_destroy(&ns->idr);
 	kmem_cache_free(pid_ns_cachep, ns);
@@ -137,12 +149,28 @@ static void delayed_free_pidns(struct rcu_head *p)
 
 static void destroy_pid_namespace(struct pid_namespace *ns)
 {
+	unregister_pidns_sysctls(ns);
+
 	ns_free_inum(&ns->ns);
 
 	idr_destroy(&ns->idr);
 	call_rcu(&ns->rcu, delayed_free_pidns);
 }
 
+static void destroy_pid_namespace_work(struct work_struct *work)
+{
+	struct pid_namespace *ns =
+		container_of(work, struct pid_namespace, work);
+
+	do {
+		struct pid_namespace *parent;
+
+		parent = ns->parent;
+		destroy_pid_namespace(ns);
+		ns = parent;
+	} while (ns != &init_pid_ns && refcount_dec_and_test(&ns->ns.count));
+}
+
 struct pid_namespace *copy_pid_ns(unsigned long flags,
 	struct user_namespace *user_ns, struct pid_namespace *old_ns)
 {
@@ -155,15 +183,8 @@ struct pid_namespace *copy_pid_ns(unsigned long flags,
 
 void put_pid_ns(struct pid_namespace *ns)
 {
-	struct pid_namespace *parent;
-
-	while (ns != &init_pid_ns) {
-		parent = ns->parent;
-		if (!refcount_dec_and_test(&ns->ns.count))
-			break;
-		destroy_pid_namespace(ns);
-		ns = parent;
-	}
+	if (ns && ns != &init_pid_ns && refcount_dec_and_test(&ns->ns.count))
+		schedule_work(&ns->work);
 }
 EXPORT_SYMBOL_GPL(put_pid_ns);
 
@@ -218,6 +239,7 @@ void zap_pid_ns_processes(struct pid_namespace *pid_ns)
 	 */
 	do {
 		clear_thread_flag(TIF_SIGPENDING);
+		clear_thread_flag(TIF_NOTIFY_SIGNAL);
 		rc = kernel_wait4(-1, NULL, __WALL, NULL);
 	} while (rc != -ECHILD);
 
@@ -248,24 +270,7 @@ void zap_pid_ns_processes(struct pid_namespace *pid_ns)
 		set_current_state(TASK_INTERRUPTIBLE);
 		if (pid_ns->pid_allocated == init_pids)
 			break;
-		/*
-		 * Release tasks_rcu_exit_srcu to avoid following deadlock:
-		 *
-		 * 1) TASK A unshare(CLONE_NEWPID)
-		 * 2) TASK A fork() twice -> TASK B (child reaper for new ns)
-		 *    and TASK C
-		 * 3) TASK B exits, kills TASK C, waits for TASK A to reap it
-		 * 4) TASK A calls synchronize_rcu_tasks()
-		 *                   -> synchronize_srcu(tasks_rcu_exit_srcu)
-		 * 5) *DEADLOCK*
-		 *
-		 * It is considered safe to release tasks_rcu_exit_srcu here
-		 * because we assume the current task can not be concurrently
-		 * reaped at this point.
-		 */
-		exit_tasks_rcu_stop();
 		schedule();
-		exit_tasks_rcu_start();
 	}
 	__set_current_state(TASK_RUNNING);
 
@@ -277,7 +282,7 @@ void zap_pid_ns_processes(struct pid_namespace *pid_ns)
 }
 
 #ifdef CONFIG_CHECKPOINT_RESTORE
-static int pid_ns_ctl_handler(struct ctl_table *table, int write,
+static int pid_ns_ctl_handler(const struct ctl_table *table, int write,
 		void *buffer, size_t *lenp, loff_t *ppos)
 {
 	struct pid_namespace *pid_ns = task_active_pid_ns(current);
@@ -290,6 +295,7 @@ static int pid_ns_ctl_handler(struct ctl_table *table, int write,
 	next = idr_get_cursor(&pid_ns->idr) - 1;
 
 	tmp.data = &next;
+	tmp.extra2 = &pid_ns->pid_max;
 	ret = proc_dointvec_minmax(&tmp, write, buffer, lenp, ppos);
 	if (!ret && write)
 		idr_set_cursor(&pid_ns->idr, next + 1);
@@ -297,17 +303,15 @@ static int pid_ns_ctl_handler(struct ctl_table *table, int write,
 	return ret;
 }
 
-extern int pid_max;
-static struct ctl_table pid_ns_ctl_table[] = {
+static const struct ctl_table pid_ns_ctl_table[] = {
 	{
 		.procname = "ns_last_pid",
 		.maxlen = sizeof(int),
 		.mode = 0666, /* permissions are checked in the handler */
 		.proc_handler = pid_ns_ctl_handler,
 		.extra1 = SYSCTL_ZERO,
-		.extra2 = &pid_max,
+		.extra2 = &init_pid_ns.pid_max,
 	},
-	{ }
 };
 #endif	/* CONFIG_CHECKPOINT_RESTORE */