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=-12.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 0ADCBC388F7 for ; Wed, 28 Oct 2020 21:44:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id ABA0E24724 for ; Wed, 28 Oct 2020 21:44:11 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=bytedance-com.20150623.gappssmtp.com header.i=@bytedance-com.20150623.gappssmtp.com header.b="JRG9qhqW" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726663AbgJ1VoH (ORCPT ); Wed, 28 Oct 2020 17:44:07 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47638 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726495AbgJ1VoF (ORCPT ); Wed, 28 Oct 2020 17:44:05 -0400 Received: from mail-oi1-x242.google.com (mail-oi1-x242.google.com [IPv6:2607:f8b0:4864:20::242]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D1E8AC0613CF for ; Wed, 28 Oct 2020 14:44:05 -0700 (PDT) Received: by mail-oi1-x242.google.com with SMTP id k27so1095842oij.11 for ; Wed, 28 Oct 2020 14:44:05 -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=f42zNGuydbxsMprn7/o4rTiW5Mh/YrWQVTbGkrcpGAU=; b=JRG9qhqWVdv+qAPGEyd6hAeN94upYYLiFE/8ziCyK2IfmG0KH0vcgx4BU3gjZFhSCf OEaj1GD1WXVm1jmeXl1DAWeAzX9Lob3XEKoPsdIGbnDQ1EZlxhf90ONNi7wNxTQIRxa9 JYfxxPzpE73/OCT2b00zuaCJtatE4mhFQZTM1zuzRudG7zsEUnH4gtecsO/0Msaf4j7w CHNZUDlEGkeM+dWh/h54KR874ZVAd/8idZH6gFDdGIdh0J1HKh15Z6JSbBjt3nBo17Ag izJQJtcjN0Ho2qCL3Miw31aUHdSVubCbCTwrcvEvzj7CbUF9eK85qoW+4YUKLq/JBNAg 8XsA== 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=f42zNGuydbxsMprn7/o4rTiW5Mh/YrWQVTbGkrcpGAU=; b=Jm5miAZl6YoFkViWmD+cAOtQwvi1lS65bnHlSOoh7dFsLNNTcfFTVTb5YdYDl8Oa8M McHbW0UBxD2skHocv3OQZbkw1fisQ1FgRfQ1K64j+zTGYOnPUwfJEcAWorJtAA7EAluM K6+wNUML9SWOzLr0519MMag3b9ikfyIEcSqL7LIJTtSL+0meSNdg7+r1egw32DJFnUdp y+6GZmoRLEhYSUjLYefqJ131uiJUuYwnzGVJFTea1/IOl94dp9FyGHKv7Qw4TdlIZ4RC wK8u/5E71BbOpuJNs90Yl09uEn4qM9ZVvbIG90YU0J3xFp7w0I/zfeuubsL/WX7AiC9S oyEQ== X-Gm-Message-State: AOAM5310q63C0Q2+zghzGkO3y/wMSpV8m2lYT8epjJywaaROlhHnBeqo A8JadfypfSxeuiz9NBi9QFp5KdT0Ud4H5sJx X-Google-Smtp-Source: ABdhPJyMlM5OFcaQWKTSVzpQLorRg0eUkIPGImJyauZgOd1B4JNiA5dI9gI84a4KFGgTpJ2ovwTXOA== X-Received: by 2002:a17:90b:1392:: with SMTP id hr18mr4756699pjb.182.1603857057592; Tue, 27 Oct 2020 20:50:57 -0700 (PDT) Received: from Smcdef-MBP.local.net ([103.136.220.89]) by smtp.gmail.com with ESMTPSA id s8sm3412273pjn.46.2020.10.27.20.50.50 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Tue, 27 Oct 2020 20:50:56 -0700 (PDT) From: Muchun Song To: hannes@cmpxchg.org, mhocko@kernel.org, vdavydov.dev@gmail.com, akpm@linux-foundation.org, shakeelb@google.com, guro@fb.com, iamjoonsoo.kim@lge.com, laoar.shao@gmail.com, chris@chrisdown.name, christian.brauner@ubuntu.com, peterz@infradead.org, mingo@kernel.org, keescook@chromium.org, tglx@linutronix.de, esyr@redhat.com, surenb@google.com, areber@redhat.com, elver@google.com Cc: linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, linux-mm@kvack.org, Muchun Song Subject: [PATCH v2] mm: memcg/slab: Fix use after free in obj_cgroup_charge Date: Wed, 28 Oct 2020 11:50:11 +0800 Message-Id: <20201028035013.99711-2-songmuchun@bytedance.com> X-Mailer: git-send-email 2.21.0 (Apple Git-122) In-Reply-To: <20201028035013.99711-1-songmuchun@bytedance.com> References: <20201028035013.99711-1-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 to memcg. If the whole process of a cgroup offlining is completed between reading a objcg->memcg pointer and bumping the css reference on another CPU, and there are exactly 0 external references to this memory cgroup (how we get to the obj_cgroup_charge() then?), css_get() can change the ref counter from 0 back to 1. Fixes: bf4f059954dc ("mm: memcg/slab: obj_cgroup API") Signed-off-by: Muchun Song Acked-by: Roman Gushchin --- changelog in v2: 1. Add unlikely and update the commit log suggested by Roman. mm/memcontrol.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 8c8b4c3ed5a0..d9cdf899c6fc 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -3221,8 +3221,10 @@ int obj_cgroup_charge(struct obj_cgroup *objcg, gfp_t gfp, size_t size) * independently later. */ rcu_read_lock(); +retry: memcg = obj_cgroup_memcg(objcg); - css_get(&memcg->css); + if (unlikely(!css_tryget(&memcg->css))) + goto retry; rcu_read_unlock(); nr_pages = size >> PAGE_SHIFT; -- 2.20.1