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Thu, 29 Jul 2021 14:44:00 +0800 (CST) Received: from dggpemm500001.china.huawei.com (7.185.36.107) by dggemv711-chm.china.huawei.com (10.1.198.66) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2176.2; Thu, 29 Jul 2021 14:48:45 +0800 Received: from [10.174.177.243] (10.174.177.243) by dggpemm500001.china.huawei.com (7.185.36.107) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2176.2; Thu, 29 Jul 2021 14:48:44 +0800 Subject: Re: [PATCH v2] mm/memcg: fix NULL pointer dereference in memcg_slab_free_hook() To: Wang Hai , , , , , , , , , , CC: , References: <20210728145655.274476-1-wanghai38@huawei.com> From: Kefeng Wang Message-ID: <277efd2a-e2eb-5d45-150b-8885b571eef7@huawei.com> Date: Thu, 29 Jul 2021 14:48:44 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: <20210728145655.274476-1-wanghai38@huawei.com> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US X-Originating-IP: [10.174.177.243] X-ClientProxiedBy: dggems701-chm.china.huawei.com (10.3.19.178) To dggpemm500001.china.huawei.com (7.185.36.107) X-CFilter-Loop: Reflected X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 08F52100B7F7 Authentication-Results: imf12.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=huawei.com; spf=pass (imf12.hostedemail.com: domain of wangkefeng.wang@huawei.com designates 45.249.212.189 as permitted sender) smtp.mailfrom=wangkefeng.wang@huawei.com X-Stat-Signature: ofbhb5mhuxtmtmpsegif5e9nbzxwse4i X-HE-Tag: 1627541329-940896 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 2021/7/28 22:56, Wang Hai wrote: > When I use kfree_rcu() to free a large memory allocated by > kmalloc_node(), the following dump occurs. > > BUG: kernel NULL pointer dereference, address: 0000000000000020 > [...] > Oops: 0000 [#1] SMP > [...] > Workqueue: events kfree_rcu_work > RIP: 0010:__obj_to_index include/linux/slub_def.h:182 [inline] > RIP: 0010:obj_to_index include/linux/slub_def.h:191 [inline] > RIP: 0010:memcg_slab_free_hook+0x120/0x260 mm/slab.h:363 > [...] > Call Trace: > kmem_cache_free_bulk+0x58/0x630 mm/slub.c:3293 > kfree_bulk include/linux/slab.h:413 [inline] > kfree_rcu_work+0x1ab/0x200 kernel/rcu/tree.c:3300 > process_one_work+0x207/0x530 kernel/workqueue.c:2276 > worker_thread+0x320/0x610 kernel/workqueue.c:2422 > kthread+0x13d/0x160 kernel/kthread.c:313 > ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294 > > When kmalloc_node() a large memory, page is allocated, not slab, > so when freeing memory via kfree_rcu(), this large memory should not > be used by memcg_slab_free_hook(), because memcg_slab_free_hook() is > is used for slab. > > Using page_objcgs_check() instead of page_objcgs() in > memcg_slab_free_hook() to fix this bug. > > Fixes: 270c6a71460e ("mm: memcontrol/slab: Use helpers to access slab page's memcg_data") > Signed-off-by: Wang Hai Reviewed-by: Kefeng Wang > --- > v1->v2: Use page_objcgs_check() to fix this bug > mm/slab.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/slab.h b/mm/slab.h > index 67e06637ff2e..59db4797acd4 100644 > --- a/mm/slab.h > +++ b/mm/slab.h > @@ -339,7 +339,7 @@ static inline void memcg_slab_free_hook(struct kmem_cache *s_orig, > continue; > > page = virt_to_head_page(p[i]); > - objcgs = page_objcgs(page); > + objcgs = page_objcgs_check(page); > if (!objcgs) > continue; >