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=-8.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, 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 AEDE8C433E0 for ; Mon, 22 Mar 2021 14:46:40 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 1271C61925 for ; Mon, 22 Mar 2021 14:46:40 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1271C61925 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=cmpxchg.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id E806A6B00CE; Mon, 22 Mar 2021 10:27:48 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id E570A6B00D0; Mon, 22 Mar 2021 10:27:48 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id CD1FA6B00D1; Mon, 22 Mar 2021 10:27:48 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0207.hostedemail.com [216.40.44.207]) by kanga.kvack.org (Postfix) with ESMTP id ADFE86B00CE for ; Mon, 22 Mar 2021 10:27:48 -0400 (EDT) Received: from smtpin25.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 21E3D8249980 for ; Mon, 22 Mar 2021 14:46:39 +0000 (UTC) X-FDA: 77947786518.25.B1233B0 Received: from mail-qt1-f176.google.com (mail-qt1-f176.google.com [209.85.160.176]) by imf30.hostedemail.com (Postfix) with ESMTP id 4D33CE016179 for ; Mon, 22 Mar 2021 14:46:34 +0000 (UTC) Received: by mail-qt1-f176.google.com with SMTP id u7so12455225qtq.12 for ; Mon, 22 Mar 2021 07:46:33 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cmpxchg-org.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=LwwnXFrLJnjJK1iTIncYeeyDCl9ARKzeYZnwE7/jyYA=; b=KsBF+YAnPzSXjFXRnm6tVwPLjHs3YhsYQl5RyLcz5tzGNkY/Q6qBhoK8AmhSheWK25 TZwkVUmS9tM/PRPFRrbpM2u4Cyn3gSkyYIWpnUDwuOm3Ged3K+IAlFW24waNNUZ6FuN3 1XK493tlGJ+LAuWEFx8FRyISCiYgUQ1ISjWoNGoCALsyG2YzzSyp2TOzQ7DdyciI+Efk JrZgXDCDkwogxShrQGeugyK85vvPCDi/mp6CG/ZQWHaImSOGpiy6dZp6TlasGD+9DwWb yWHXxLdMeGpIBYGSuHzcfmDbAXsIMlGEWd6sDMF+DPFIbHaoXZm0r25XoI+VAB/6Hnkf vJHQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=LwwnXFrLJnjJK1iTIncYeeyDCl9ARKzeYZnwE7/jyYA=; b=kRtts/nTjgeceCbueAIg3s3fajs6+ch+ptSu6JvKEDbXdhI1bfziAm2dHc4QgEgSAJ 4J03B/B1qkIGdMNaopZWFY8sxKlHHCDJLHs6iLhNFKzyHHOHDu0rwcHApYG0gg/CMxv1 44xprl82nUSRXvPKBZZzfNaRTtm/HmSDYzwbHBO6ILZ/rPfJzjkpNxD9SEqgE5tmclrR woaFy9xFmPAGSQyybKajMPcu29CqnaswFxzXSmtQ2JKm4Yffcl5ABQP4kK4VFoiigGvb teC2xSKMfM+vcaa2RafrgFDnSHS+om9AfsKvisnszNzB1aPvCMEXtHx0v7ltie2XasrK FXTA== X-Gm-Message-State: AOAM530XVEM9oXlX1hkprVPGaG5ZdYuTLeq8kCVItL/7wpcBgG1Kq6yc VjU1lSacKcBuTBquwXEcksszpw== X-Google-Smtp-Source: ABdhPJyUMaJBj7uazV7Won79dwd1MktbU4kfxK+q/Fp3fbR1HGtEeJy0mla0kyQ+l4HPupZufpwPQw== X-Received: by 2002:a05:622a:174f:: with SMTP id l15mr197686qtk.197.1616424388400; Mon, 22 Mar 2021 07:46:28 -0700 (PDT) Received: from localhost ([2620:10d:c091:480::1:b54e]) by smtp.gmail.com with ESMTPSA id z11sm11229785qkg.52.2021.03.22.07.46.27 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 22 Mar 2021 07:46:28 -0700 (PDT) Date: Mon, 22 Mar 2021 10:46:26 -0400 From: Johannes Weiner To: Muchun Song Cc: guro@fb.com, mhocko@kernel.org, akpm@linux-foundation.org, shakeelb@google.com, vdavydov.dev@gmail.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, duanxiongchun@bytedance.com Subject: Re: [PATCH v5 1/7] mm: memcontrol: slab: fix obtain a reference to a freeing memcg Message-ID: References: <20210319163821.20704-1-songmuchun@bytedance.com> <20210319163821.20704-2-songmuchun@bytedance.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210319163821.20704-2-songmuchun@bytedance.com> X-Stat-Signature: 91weuku3p8t6adnfu1bwj53uqo68pjpn X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 4D33CE016179 Received-SPF: none (cmpxchg.org>: No applicable sender policy available) receiver=imf30; identity=mailfrom; envelope-from=""; helo=mail-qt1-f176.google.com; client-ip=209.85.160.176 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1616424394-768156 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 Sat, Mar 20, 2021 at 12:38:14AM +0800, Muchun Song wrote: > The rcu_read_lock/unlock only can guarantee that the memcg will not be > freed, but it cannot guarantee the success of css_get (which is in the > refill_stock when cached memcg changed) to memcg. > > rcu_read_lock() > memcg = obj_cgroup_memcg(old) > __memcg_kmem_uncharge(memcg) > refill_stock(memcg) > if (stock->cached != memcg) > // css_get can change the ref counter from 0 back to 1. > css_get(&memcg->css) > rcu_read_unlock() > > This fix is very like the commit: > > eefbfa7fd678 ("mm: memcg/slab: fix use after free in obj_cgroup_charge") > > Fix this by holding a reference to the memcg which is passed to the > __memcg_kmem_uncharge() before calling __memcg_kmem_uncharge(). > > Fixes: 3de7d4f25a74 ("mm: memcg/slab: optimize objcg stock draining") > Signed-off-by: Muchun Song Acked-by: Johannes Weiner Good catch! Did you trigger the WARN_ON() in percpu_ref_kill_and_confirm() during testing?