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[195.135.220.15]) by mx.google.com with ESMTPS id r18si13905903ejp.141.2019.07.28.23.25.01 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 28 Jul 2019 23:25:02 -0700 (PDT) Received-SPF: softfail (google.com: domain of transitioning mhocko@kernel.org does not designate 195.135.220.15 as permitted sender) client-ip=195.135.220.15; Authentication-Results: mx.google.com; spf=softfail (google.com: domain of transitioning mhocko@kernel.org does not designate 195.135.220.15 as permitted sender) smtp.mailfrom=mhocko@kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=kernel.org X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 765A3ADFC; Mon, 29 Jul 2019 06:25:01 +0000 (UTC) Date: Mon, 29 Jul 2019 08:25:00 +0200 From: Michal Hocko To: Miles Chen Cc: Johannes Weiner , Vladimir Davydov , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-mediatek@lists.infradead.org, wsd_upstream@mediatek.com Subject: Re: [PATCH v2] mm: memcontrol: fix use after free in mem_cgroup_iter() Message-ID: <20190729062500.GB9330@dhcp22.suse.cz> References: <20190726021247.16162-1-miles.chen@mediatek.com> <20190726124933.GN6142@dhcp22.suse.cz> <20190726125533.GO6142@dhcp22.suse.cz> <1564184878.19817.5.camel@mtkswgap22> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1564184878.19817.5.camel@mtkswgap22> User-Agent: Mutt/1.10.1 (2018-07-13) 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 27-07-19 07:47:58, Miles Chen wrote: > On Fri, 2019-07-26 at 14:55 +0200, Michal Hocko wrote: [...] > > > I am sorry, I didn't get to comment an earlier version but I am > > > wondering whether it makes more sense to do and explicit invalidation. > > > > > I think we should keep the original v2 version, the reason is the > !use_hierarchy does not imply we can reach root_mem_cgroup: > > cd /sys/fs/cgroup/memory/0 > mkdir 1 > cd /sys/fs/cgroup/memory/0/1 > echo 1 > memory.use_hierarchy // only 1 and its children has > use_hierarchy set > mkdir 2 > > rmdir 2 // parent_mem_cgroup(2) goes up to 1 You are right I have missed this case. I am not sure anybody is using layout like that but your fix is more robust and catches that case as well. Acked-by: Michal Hocko -- Michal Hocko SUSE Labs