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=-16.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT 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 946CEC433C1 for ; Fri, 19 Mar 2021 16:39:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6C4E06197D for ; Fri, 19 Mar 2021 16:39:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230136AbhCSQjG (ORCPT ); Fri, 19 Mar 2021 12:39:06 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54986 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229973AbhCSQim (ORCPT ); Fri, 19 Mar 2021 12:38:42 -0400 Received: from mail-pg1-x534.google.com (mail-pg1-x534.google.com [IPv6:2607:f8b0:4864:20::534]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C7AC3C06174A for ; Fri, 19 Mar 2021 09:38:42 -0700 (PDT) Received: by mail-pg1-x534.google.com with SMTP id k24so4047226pgl.6 for ; Fri, 19 Mar 2021 09:38:42 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bytedance-com.20150623.gappssmtp.com; s=20150623; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=q1x9F0RxytCzXg/daJ/mfbteZTYPjROB2MKRFPS4wa0=; b=DEMZOb2ZxxtpsbPJtNeCUdXVflxX0xnzNmd0okHPwRSj8fPXt7AUSn/411t7ZnSc1V mE6TsuZKMqrrwsil/GbrCJeIPHzCu+25dTYIxKzm72VWt6NO59WeZZ/QsJXqR4CRuZqT GBQHQIn2nlJmGOJnLFb4R9rm8pEvGE2Fj31DotWldMM1g9KRLtxBLhv0rtLzgXoYMTad ACquv1g/mbCZGDrX0KrYzoofSH5h9SeC1S2Qdo5hDoHUV/ZeC5WIruC2QrNrjBoJTyO8 vZ/tDIROyr5ka6LxC/5tIDXSLbKKMHZ8l6DyHC79+09L6/f/bFKZHMYFCJqtclTkXpT6 T12g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=q1x9F0RxytCzXg/daJ/mfbteZTYPjROB2MKRFPS4wa0=; b=IjB/UAfvBUHIG23nXSUjYTOTlqQK5h5tlZevxEqiJrdAz6rpmprUJe+bvBBWVFyYNT e2hC8pX8/JelkNrZhYzLcpgTKePcI+y/3UbijbyGlw8ZqcrAOkceUCEl4D7CkTonNh3T gBZk0BT8XvzeJuXcOo1demxMXKtGCABdhh5M6uBe3UMMdz3PtF1t72hebgqt4KOJHuXU xUS8SRc2z7RJWuKSw4I+u7HjhvOMsDxjnrXFbAu0H+28PpsJwmFvYwl1k4tMJ0wUdSaH u4aTf4CJSR6SZ50zWK0ptdfaZGAmNNohLjmahbGlvCyfj+jrFMc3/x0Qn2+j7BP1iu2M UTZQ== X-Gm-Message-State: AOAM530B8pjvYicgAt8OAb/HbSU4+94/z4kpC81TyI6T+4gWr0loN/vj Ka0Dn+h54EFzuNXvy9sFhVjkWQcWQepVCbzm X-Google-Smtp-Source: ABdhPJzv6KoFJsnEXmVe1wLnx5vlmo8q+uLsN4x2hPYnirz8Y5YOPeFFmr8wTjnjzbdpJXF6MUvWAQ== X-Received: by 2002:a63:fb18:: with SMTP id o24mr11855982pgh.55.1616171922411; Fri, 19 Mar 2021 09:38:42 -0700 (PDT) Received: from localhost.bytedance.net ([139.177.225.231]) by smtp.gmail.com with ESMTPSA id z25sm5860239pfn.37.2021.03.19.09.38.38 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Fri, 19 Mar 2021 09:38:42 -0700 (PDT) From: Muchun Song To: guro@fb.com, hannes@cmpxchg.org, mhocko@kernel.org, akpm@linux-foundation.org, shakeelb@google.com, vdavydov.dev@gmail.com Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, duanxiongchun@bytedance.com, Muchun Song Subject: [PATCH v5 1/7] mm: memcontrol: slab: fix obtain a reference to a freeing memcg Date: Sat, 20 Mar 2021 00:38:14 +0800 Message-Id: <20210319163821.20704-2-songmuchun@bytedance.com> X-Mailer: git-send-email 2.21.0 (Apple Git-122) In-Reply-To: <20210319163821.20704-1-songmuchun@bytedance.com> References: <20210319163821.20704-1-songmuchun@bytedance.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 --- mm/memcontrol.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 845eec01ef9d..2cda76ff0629 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -3181,9 +3181,17 @@ static void drain_obj_stock(struct memcg_stock_pcp *stock) unsigned int nr_bytes = stock->nr_bytes & (PAGE_SIZE - 1); if (nr_pages) { + struct mem_cgroup *memcg; + rcu_read_lock(); - __memcg_kmem_uncharge(obj_cgroup_memcg(old), nr_pages); +retry: + memcg = obj_cgroup_memcg(old); + if (unlikely(!css_tryget(&memcg->css))) + goto retry; rcu_read_unlock(); + + __memcg_kmem_uncharge(memcg, nr_pages); + css_put(&memcg->css); } /* -- 2.11.0