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=-15.7 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=unavailable 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 CC5A5C2BB40 for ; Tue, 15 Dec 2020 03:07:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9DAC3224F4 for ; Tue, 15 Dec 2020 03:07:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726144AbgLODHV (ORCPT ); Mon, 14 Dec 2020 22:07:21 -0500 Received: from mail.kernel.org ([198.145.29.99]:35182 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725974AbgLODHQ (ORCPT ); Mon, 14 Dec 2020 22:07:16 -0500 Date: Mon, 14 Dec 2020 19:06:35 -0800 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1608001596; bh=p2/fELHAYg6nST8U+7iCRiH6jBhYCBTMR7xj6/Kw7GA=; h=From:To:Subject:In-Reply-To:From; b=nWZGSob23pbztHHZEU9O1lSwpKbZOsBe+p4d0waDRuUUqHzivrtzajW3F5oY2lJ2a ZWexw1iXp3M9zsVTPpcqoJlY+CZwdWSMaVTf/RJfO8egCYSJfxnM880q/of2YTvsZe ECV6N/W0FQG/Fe1Aa+BdxcDVfNNCPOQYFaDZbfv8= From: Andrew Morton To: akpm@linux-foundation.org, chris@chrisdown.name, christian.brauner@ubuntu.com, guro@fb.com, hannes@cmpxchg.org, iamjoonsoo.kim@lge.com, laoar.shao@gmail.com, linux-mm@kvack.org, mhocko@kernel.org, mm-commits@vger.kernel.org, shakeelb@google.com, songmuchun@bytedance.com, torvalds@linux-foundation.org, vdavydov.dev@gmail.com Subject: [patch 059/200] mm: memcg/slab: fix use after free in obj_cgroup_charge Message-ID: <20201215030635.lLOIalSP1%akpm@linux-foundation.org> In-Reply-To: <20201214190237.a17b70ae14f129e2dca3d204@linux-foundation.org> User-Agent: s-nail v14.8.16 Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org From: Muchun Song Subject: mm: memcg/slab: fix use after free in obj_cgroup_charge 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. Link: https://lkml.kernel.org/r/20201028035013.99711-2-songmuchun@bytedance.com Fixes: bf4f059954dc ("mm: memcg/slab: obj_cgroup API") Signed-off-by: Muchun Song Acked-by: Roman Gushchin Reviewed-by: Shakeel Butt Cc: Johannes Weiner Cc: Michal Hocko Cc: Vladimir Davydov Cc: Joonsoo Kim Cc: Yafang Shao Cc: Chris Down Cc: Christian Brauner Signed-off-by: Andrew Morton --- mm/memcontrol.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) --- a/mm/memcontrol.c~mm-memcg-slab-fix-use-after-free-in-obj_cgroup_charge +++ a/mm/memcontrol.c @@ -3235,8 +3235,10 @@ int obj_cgroup_charge(struct obj_cgroup * 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; _