[PATCH 4/5] mm, memcg: avoid possible NULL pointer dereferencing in mem_cgroup_init()

From: Miaohe Lin <linmiaohe@huawei.com>
To: <hannes@cmpxchg.org>, <mhocko@kernel.org>,
	<vdavydov.dev@gmail.com>, <akpm@linux-foundation.org>
Cc: <shakeelb@google.com>, <guro@fb.com>, <willy@infradead.org>,
	<alexs@kernel.org>, <richard.weiyang@gmail.com>,
	<songmuchun@bytedance.com>, <linux-mm@kvack.org>,
	<linux-kernel@vger.kernel.org>, <cgroups@vger.kernel.org>,
	<linmiaohe@huawei.com>
Subject: [PATCH 4/5] mm, memcg: avoid possible NULL pointer dereferencing in mem_cgroup_init()
Date: Thu, 29 Jul 2021 20:57:54 +0800	[thread overview]
Message-ID: <20210729125755.16871-5-linmiaohe@huawei.com> (raw)
In-Reply-To: <20210729125755.16871-1-linmiaohe@huawei.com>

rtpn might be NULL in very rare case. We have better to check it before
dereferencing it. Since memcg can live with NULL rb_tree_per_node in
soft_limit_tree, warn this case and continue.

Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
---
 mm/memcontrol.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 5b4592d1e0f2..70a32174e7c4 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -7109,6 +7109,8 @@ static int __init mem_cgroup_init(void)
 		rtpn = kzalloc_node(sizeof(*rtpn), GFP_KERNEL,
 				    node_online(node) ? node : NUMA_NO_NODE);
 
+		if (WARN_ON_ONCE(!rtpn))
+			continue;
 		rtpn->rb_root = RB_ROOT;
 		rtpn->rb_rightmost = NULL;
 		spin_lock_init(&rtpn->lock);
-- 
2.23.0

