Fix failure path in alloc_pid()

commit 1a80dade010c7a7f4885a4c4c2a7ac22cc7b34df upstream.

The failure path removes the allocated PIDs from the wrong namespace.
This could lead to us inadvertently reusing PIDs in the leaf namespace
and leaking PIDs in parent namespaces.

Fixes: 95846ecf ("pid: replace pid bitmap implementation with IDR API")
Cc: <stable@vger.kernel.org>
Signed-off-by: NMatthew Wilcox <willy@infradead.org>
Acked-by: N"Eric W. Biederman" <ebiederm@xmission.com>
Reviewed-by: NOleg Nesterov <oleg@redhat.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

kernel/pid.c

@@ -233,8 +233,10 @@ struct pid *alloc_pid(struct pid_namespace *ns)
 
 out_free:
 	spin_lock_irq(&pidmap_lock);
-	while (++i <= ns->level)
-		idr_remove(&ns->idr, (pid->numbers + i)->nr);
+	while (++i <= ns->level) {
+		upid = pid->numbers + i;
+		idr_remove(&upid->ns->idr, upid->nr);
+	}
 
 	/* On failure to allocate the first pid, reset the state */
 	if (ns->pid_allocated == PIDNS_ADDING)