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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 66DA8C48BF6 for ; Wed, 21 Feb 2024 10:08:08 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id D532C6B0078; Wed, 21 Feb 2024 05:08:07 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id D02E36B007B; Wed, 21 Feb 2024 05:08:07 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id BA4216B0081; Wed, 21 Feb 2024 05:08:07 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id A7B796B0078 for ; Wed, 21 Feb 2024 05:08:07 -0500 (EST) Received: from smtpin07.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay09.hostedemail.com (Postfix) with ESMTP id 7453180A0D for ; Wed, 21 Feb 2024 10:08:07 +0000 (UTC) X-FDA: 81815385414.07.A70FA33 Received: from smtp-out2.suse.de (smtp-out2.suse.de [195.135.223.131]) by imf11.hostedemail.com (Postfix) with ESMTP id 81C0F40013 for ; Wed, 21 Feb 2024 10:08:04 +0000 (UTC) Authentication-Results: imf11.hostedemail.com; dkim=pass header.d=suse.com header.s=susede1 header.b=BAbuwTrz; dkim=pass header.d=suse.com header.s=susede1 header.b=eznXXzg4; spf=pass (imf11.hostedemail.com: domain of mhocko@suse.com designates 195.135.223.131 as permitted sender) smtp.mailfrom=mhocko@suse.com; dmarc=pass (policy=quarantine) header.from=suse.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1708510084; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=xZGJ3olY1kWj1dk7MtZO1ibtEdnIoZrzoUYLjjxmvX0=; b=wz5VoigUsn88nfQruhA/Qxnn3vwg27NWjS0+8SA3NGm9XCHfWUGK/Kfn/7PG+w3RepPbYN Ra9SY2SRJm2RGpXNnBOW83e0fgtcKujVcMe4Y/08xe4ilP+ecZatl1hccH5dkrlQm6qltU GyfunfpjHyTIwYALqMViKTgKO4Ri7YE= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1708510084; a=rsa-sha256; cv=none; b=ccQNOKUSYC96lM/oi0rjwYXgZ8EtH1zaFA5tHdSVND/7S+Sm//11CZ7mETKyF4tfVFU3rt NC6rL8EwCakOmZqdGz8Z5c8+/+dzrvEj5DiYcCdgjgZv/mb4iZrQEe8cWDmVjWyNikilNB gc9J3s82Bm1H0fqA9oFZv/kjVK0b5S4= ARC-Authentication-Results: i=1; imf11.hostedemail.com; dkim=pass header.d=suse.com header.s=susede1 header.b=BAbuwTrz; dkim=pass header.d=suse.com header.s=susede1 header.b=eznXXzg4; spf=pass (imf11.hostedemail.com: domain of mhocko@suse.com designates 195.135.223.131 as permitted sender) smtp.mailfrom=mhocko@suse.com; dmarc=pass (policy=quarantine) header.from=suse.com Received: from imap1.dmz-prg2.suse.org (imap1.dmz-prg2.suse.org [IPv6:2a07:de40:b281:104:10:150:64:97]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by smtp-out2.suse.de (Postfix) with ESMTPS id C9C9A1FB4A; Wed, 21 Feb 2024 10:08:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1708510083; 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=xZGJ3olY1kWj1dk7MtZO1ibtEdnIoZrzoUYLjjxmvX0=; b=BAbuwTrzJs/DVFKRHFbDFTMrOfHETXJMisKC7tj8M6JjdNEOXo93jcYFaNdeQJjEAyfekQ CrWyK55GtVGUQVgEG0K6dxNYX167qbb3oWip8LFfLjTQ6Xe1gF1jehGKrTY0i0DAvPcKNH EDKodBHi1qarR9EShsI0U7wX2BQobl8= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1708510082; 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=xZGJ3olY1kWj1dk7MtZO1ibtEdnIoZrzoUYLjjxmvX0=; b=eznXXzg4qM0A3TmtjnVpTQmOa20c6dDKPyNZj3w3j7MVgFsxv/M5WS8FbQNP/f2QOO1VnF nvww1JNkoDaOiWtTt/Vga4ezs7hNrjfk0TWvaU7SBvELlCYWYPJglPfWuXzv/l7B1nQyfm HFJxqzEV5z/gbJCCXo07IFcHySDtCEE= Received: from imap1.dmz-prg2.suse.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by imap1.dmz-prg2.suse.org (Postfix) with ESMTPS id AA4A813A69; Wed, 21 Feb 2024 10:08:02 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id qRKQJoLL1WXHQAAAD6G6ig (envelope-from ); Wed, 21 Feb 2024 10:08:02 +0000 Date: Wed, 21 Feb 2024 11:08:02 +0100 From: Michal Hocko To: Gong Ruiqi Cc: linux-kernel@vger.kernel.org, stable@vger.kernel.org, Johannes Weiner , Roman Gushchin , Shakeel Butt , Muchun Song , cgroups@vger.kernel.org, linux-mm@kvack.org, Wang Weiyang , Xiu Jianfeng Subject: Re: [PATCH stable] memcg: add refcnt for pcpu stock to avoid UAF problem in drain_all_stock() Message-ID: References: <20240221081801.69764-1-gongruiqi1@huawei.com> <5436af7a-26d4-7c04-466a-7163d5a26040@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5436af7a-26d4-7c04-466a-7163d5a26040@huawei.com> X-Rspamd-Queue-Id: 81C0F40013 X-Rspam-User: X-Rspamd-Server: rspam11 X-Stat-Signature: kz3zj65wak5jnwpu38pk89sf6q5zshgk X-HE-Tag: 1708510084-376111 X-HE-Meta: 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 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: List-Subscribe: List-Unsubscribe: On Wed 21-02-24 17:50:27, Gong Ruiqi wrote: > > On 2024/02/21 16:38, Michal Hocko wrote: > > On Wed 21-02-24 16:18:01, GONG, Ruiqi wrote: > >> commit 1a3e1f40962c445b997151a542314f3c6097f8c3 upstream. > > > > I think it would be good to mention that this is only a partial backport > > and also explain why to do a partial rather than the full one. > > > > Okay. I think to fix this problem we should add refcnt relation between > memcg and stock, and since higher versions have achieved this, maybe > it's better to use the same code and align with them. So I put a "commit > xxx upstream" here, as requested in kernel docs[1]. So yes it's a > partial backport as we only need the stock part. I think it is sufficient to mention that this is a partial backport to minimize the fix to the bare minimum. [...] > > What does prevent from the following? > > > > refill_stock(memcgC) drain_all_stock(memcgB) > > drain_stock(memcgA) rcu_read_lock() > > css_put(old->css) memcgA = stock->cached > > mem_cgroup_is_descendant(memcgA, memcgB) UAF > > stock->cached = NULL > > > > I think it's not a problem since refill_stock() has disabled irq before > calling drain_stock(): > > refill_stock(memcgC) > local_irq_save > drain_stock(memcgA) > css_put(old->css) > <1> > stock->cached = NULL > local_irq_restore > <2> > > And since css_put(old->css) is an RCU free, memcgA would not be freed at > <1> as it's still in grace period. The actual release of memcgA could > happen only after irq is enabled (at <2>). > > And for CPU2, the access to stock->cached in drain_all_stock() is > protected by rcu_read_lock(), so from stock->cached we get either NULL, > or a memcgA that is still not freed. > > Please correct me if I have some wrong understanding to RCU. You are right. Thanks! IRQ disabling is there in one form or the other since db2ba40c277d ("mm: memcontrol: make per-cpu charge cache IRQ-safe for socket accounting") so 4.8+ is safe. Backports to older kernels would nee to pull this one as well. > >> Cc: stable@vger.kernel.org # 4.19 5.4 > >> Fixes: cdec2e4265df ("memcg: coalesce charging via percpu storage") > >> Signed-off-by: GONG, Ruiqi Acked-by: Michal Hocko Thanks! -- Michal Hocko SUSE Labs