[PATCH 2/2] exit: pidns: alloc_pid() leaks pid_namespace if child_reaper is exiting

[Oleg Nesterov <oleg@redhat.com>]

alloc_pid() does get_pid_ns() beforehand but forgets to put_pid_ns()
if it fails because disable_pid_allocation() was called by the exiting
child_reaper. We can move get_pid_ns() down to successful return.

While at it, simplify/cleanup the "goto out" mess, no need to confuse
the success/error return paths.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---
 kernel/pid.c |    7 +++----
 1 files changed, 3 insertions(+), 4 deletions(-)

diff --git a/kernel/pid.c b/kernel/pid.c
index 9b9a266..dfc2f3b 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -320,7 +320,6 @@ struct pid *alloc_pid(struct pid_namespace *ns)
 			goto out_free;
 	}
 
-	get_pid_ns(ns);
 	atomic_set(&pid->count, 1);
 	for (type = 0; type < PIDTYPE_MAX; ++type)
 		INIT_HLIST_HEAD(&pid->tasks[type]);
@@ -336,7 +335,7 @@ struct pid *alloc_pid(struct pid_namespace *ns)
 	}
 	spin_unlock_irq(&pidmap_lock);
 
-out:
+	get_pid_ns(ns);
 	return pid;
 
 out_unlock:
@@ -346,8 +345,8 @@ out_free:
 		free_pidmap(pid->numbers + i);
 
 	kmem_cache_free(ns->pid_cachep, pid);
-	pid = NULL;
-	goto out;
+out:
+	return NULL;
 }
 
 void disable_pid_allocation(struct pid_namespace *ns)
-- 
1.5.5.1