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=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 10D9DC4338F for ; Wed, 28 Jul 2021 16:44:08 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id A9D0A6101C for ; Wed, 28 Jul 2021 16:44:07 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org A9D0A6101C Authentication-Results: mail.kernel.org; dmarc=fail (p=quarantine dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id E4AAB8D0003; 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Wed, 28 Jul 2021 16:44:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1627490644; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=v4EOY6ldmDFYdioXhdFcqgF63Zm4Uf4JO8ULF+YwZqE=; b=Dt1aZCMOmON0Sr2FeZq8bnbtMMIQcxP+jPEjOTZW/bt05S/l+X3o3vIVkK0yX0xB7P4tGa CsUzGY1Q5alN3lAc5H+N5WVu0hoVwQtHbjauWaGatStK9d1BtIiV9t4KLTYqPvfWD5sCLQ vMN/sqi8JsuFT7rc0yd2g+1SAu9HGME= Received: from suse.cz (unknown [10.100.201.86]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by relay2.suse.de (Postfix) with ESMTPS id 567C0A3B8B; Wed, 28 Jul 2021 16:44:04 +0000 (UTC) Date: Wed, 28 Jul 2021 18:44:03 +0200 From: Michal Hocko To: Wang Hai Cc: cl@linux.com, penberg@kernel.org, guro@fb.com, rientjes@google.com, iamjoonsoo.kim@lge.com, akpm@linux-foundation.org, vbabka@suse.cz, hannes@cmpxchg.org, shakeelb@google.com, ast@kernel.org, wangkefeng.wang@huawei.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] mm/memcg: fix NULL pointer dereference in memcg_slab_free_hook() Message-ID: References: <20210728145655.274476-1-wanghai38@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210728145655.274476-1-wanghai38@huawei.com> Authentication-Results: imf11.hostedemail.com; dkim=pass header.d=suse.com header.s=susede1 header.b=Dt1aZCMO; spf=pass (imf11.hostedemail.com: domain of mhocko@suse.com designates 195.135.220.29 as permitted sender) smtp.mailfrom=mhocko@suse.com; dmarc=pass (policy=quarantine) header.from=suse.com X-Rspamd-Server: rspam02 X-Stat-Signature: 1iw5diff64fb99y8moo9r46qyi55b1nr X-Rspamd-Queue-Id: 96F78F009544 X-HE-Tag: 1627490645-92106 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 Wed 28-07-21 22:56:55, 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 This looks like a much better fix. Thanks! Acked-by: Michal Hocko > --- > 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; > > -- > 2.17.1 -- Michal Hocko SUSE Labs