From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.5 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8DCE1C4338F for ; Wed, 28 Jul 2021 10:49:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6DD9B60F9B for ; Wed, 28 Jul 2021 10:49:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234249AbhG1Ktk (ORCPT ); Wed, 28 Jul 2021 06:49:40 -0400 Received: from szxga03-in.huawei.com ([45.249.212.189]:12327 "EHLO szxga03-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231238AbhG1Kti (ORCPT ); Wed, 28 Jul 2021 06:49:38 -0400 Received: from dggemv704-chm.china.huawei.com (unknown [172.30.72.56]) by szxga03-in.huawei.com (SkyGuard) with ESMTP id 4GZVfW22GMz7w8V; Wed, 28 Jul 2021 18:44:51 +0800 (CST) Received: from dggpemm500001.china.huawei.com (7.185.36.107) by dggemv704-chm.china.huawei.com (10.3.19.47) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2176.2; Wed, 28 Jul 2021 18:49:34 +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; Wed, 28 Jul 2021 18:49:34 +0800 Subject: Re: [PATCH] mm/memcg: fix NULL pointer dereference in memcg_slab_free_hook() To: Wang Hai , , , , , , , , , CC: , References: <20210728091348.272714-1-wanghai38@huawei.com> From: Kefeng Wang Message-ID: <56069fc8-a8d6-e506-4f0d-9ab9ffd6f9e0@huawei.com> Date: Wed, 28 Jul 2021 18:49:33 +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: <20210728091348.272714-1-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: dggems706-chm.china.huawei.com (10.3.19.183) To dggpemm500001.china.huawei.com (7.185.36.107) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2021/7/28 17:13, 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. > > So in this case, there is no need to do anything with this large > page in memcg_slab_free_hook(), just skip it. > > Fixes: 270c6a71460e ("mm: memcontrol/slab: Use helpers to access slab page's memcg_data") > Signed-off-by: Wang Hai Reviewed-by: Kefeng Wang > --- > mm/slab.h | 15 ++++++++++----- > 1 file changed, 10 insertions(+), 5 deletions(-) > > diff --git a/mm/slab.h b/mm/slab.h > index 67e06637ff2e..247d3f9c21f7 100644 > --- a/mm/slab.h > +++ b/mm/slab.h > @@ -339,15 +339,20 @@ static inline void memcg_slab_free_hook(struct kmem_cache *s_orig, > continue; > > page = virt_to_head_page(p[i]); > + if (!s_orig) { > + if (unlikely(!PageSlab(page))) { > + BUG_ON(!PageCompound(page)); > + continue; > + } > + s = page->slab_cache; > + } else { > + s = s_orig; > + } > + > objcgs = page_objcgs(page); > if (!objcgs) > continue; > > - if (!s_orig) > - s = page->slab_cache; > - else > - s = s_orig; > - > off = obj_to_index(s, page, p[i]); > objcg = objcgs[off]; > if (!objcg)