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[195.135.220.15]) by mx.google.com with ESMTPS id d13si5723108edx.407.2019.04.29.03.59.41 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 29 Apr 2019 03:59:41 -0700 (PDT) Received-SPF: pass (google.com: domain of jslaby@suse.cz designates 195.135.220.15 as permitted sender) client-ip=195.135.220.15; Authentication-Results: mx.google.com; spf=pass (google.com: domain of jslaby@suse.cz designates 195.135.220.15 as permitted sender) smtp.mailfrom=jslaby@suse.cz 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 6F05BADE1; Mon, 29 Apr 2019 10:59:41 +0000 (UTC) From: Jiri Slaby To: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, Jiri Slaby , Johannes Weiner , Michal Hocko , Vladimir Davydov , cgroups@vger.kernel.org, Raghavendra K T Subject: [PATCH] memcg: make it work on sparse non-0-node systems Date: Mon, 29 Apr 2019 12:59:39 +0200 Message-Id: <20190429105939.11962-1-jslaby@suse.cz> X-Mailer: git-send-email 2.21.0 In-Reply-To: <359d98e6-044a-7686-8522-bdd2489e9456@suse.cz> References: <359d98e6-044a-7686-8522-bdd2489e9456@suse.cz> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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: We have a single node system with node 0 disabled: Scanning NUMA topology in Northbridge 24 Number of physical nodes 2 Skipping disabled node 0 Node 1 MemBase 0000000000000000 Limit 00000000fbff0000 NODE_DATA(1) allocated [mem 0xfbfda000-0xfbfeffff] This causes crashes in memcg when system boots: BUG: unable to handle kernel NULL pointer dereference at 0000000000000008 #PF error: [normal kernel read fault] ... RIP: 0010:list_lru_add+0x94/0x170 ... Call Trace: d_lru_add+0x44/0x50 dput.part.34+0xfc/0x110 __fput+0x108/0x230 task_work_run+0x9f/0xc0 exit_to_usermode_loop+0xf5/0x100 It is reproducible as far as 4.12. I did not try older kernels. You have to have a new enough systemd, e.g. 241 (the reason is unknown -- was not investigated). Cannot be reproduced with systemd 234. The system crashes because the size of lru array is never updated in memcg_update_all_list_lrus and the reads are past the zero-sized array, causing dereferences of random memory. The root cause are list_lru_memcg_aware checks in the list_lru code. The test in list_lru_memcg_aware is broken: it assumes node 0 is always present, but it is not true on some systems as can be seen above. So fix this by checking the first online node instead of node 0. Signed-off-by: Jiri Slaby Cc: Johannes Weiner Cc: Michal Hocko Cc: Vladimir Davydov Cc: Cc: Cc: Raghavendra K T --- mm/list_lru.c | 6 +----- 1 file changed, 1 insertion(+), 5 deletions(-) diff --git a/mm/list_lru.c b/mm/list_lru.c index 0730bf8ff39f..7689910f1a91 100644 --- a/mm/list_lru.c +++ b/mm/list_lru.c @@ -37,11 +37,7 @@ static int lru_shrinker_id(struct list_lru *lru) static inline bool list_lru_memcg_aware(struct list_lru *lru) { - /* - * This needs node 0 to be always present, even - * in the systems supporting sparse numa ids. - */ - return !!lru->node[0].memcg_lrus; + return !!lru->node[first_online_node].memcg_lrus; } static inline struct list_lru_one * -- 2.21.0