diff --git a/include/linux/pid.h b/include/linux/pid.h
index bf3af54de616..343abf22092e 100644
--- a/include/linux/pid.h
+++ b/include/linux/pid.h
@@ -67,7 +67,7 @@ struct pid
 	/* wait queue for pidfd notifications */
 	wait_queue_head_t wait_pidfd;
 	struct rcu_head rcu;
-	struct upid numbers[];
+	struct upid numbers[1];
 };
 
 extern struct pid init_struct_pid;
diff --git a/kernel/pid.c b/kernel/pid.c
index b28f928af8d4..9efcf7178b01 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -662,11 +662,8 @@ void __init pid_idr_init(void)
 
 	idr_init(&init_pid_ns.idr);
 
-	init_pid_ns.pid_cachep = kmem_cache_create("pid",
-			struct_size((struct pid *)NULL, numbers, 1),
-			__alignof__(struct pid),
-			SLAB_HWCACHE_ALIGN | SLAB_PANIC | SLAB_ACCOUNT,
-			NULL);
+	init_pid_ns.pid_cachep = KMEM_CACHE(pid,
+			SLAB_HWCACHE_ALIGN | SLAB_PANIC | SLAB_ACCOUNT);
 }
 
 static struct file *__pidfd_fget(struct task_struct *task, int fd)
diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c
index a575fabf697e..1daadbefcee3 100644
--- a/kernel/pid_namespace.c
+++ b/kernel/pid_namespace.c
@@ -47,7 +47,7 @@ static struct kmem_cache *create_pid_cachep(unsigned int level)
 		return kc;
 
 	snprintf(name, sizeof(name), "pid_%u", level + 1);
-	len = struct_size((struct pid *)NULL, numbers, level + 1);
+	len = sizeof(struct pid) + level * sizeof(struct upid);
 	mutex_lock(&pid_caches_mutex);
 	/* Name collision forces to do allocation under mutex. */
 	if (!*pkc)