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=-9.7 required=3.0 tests=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=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 89885C433DF for ; Tue, 7 Jul 2020 06:28:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 62A362075B for ; Tue, 7 Jul 2020 06:28:17 +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="Qb0ZCKir" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727999AbgGGG2P (ORCPT ); Tue, 7 Jul 2020 02:28:15 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34370 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726757AbgGGG2P (ORCPT ); Tue, 7 Jul 2020 02:28:15 -0400 Received: from mail-pf1-x443.google.com (mail-pf1-x443.google.com [IPv6:2607:f8b0:4864:20::443]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 821CAC061755 for ; Mon, 6 Jul 2020 23:28:14 -0700 (PDT) Received: by mail-pf1-x443.google.com with SMTP id s26so4363566pfm.4 for ; Mon, 06 Jul 2020 23:28:14 -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:mime-version :content-transfer-encoding; bh=eGXjfQahGJEMI3dFWEvZHra9f4CPaADa6kwDLG6Sz0U=; b=Qb0ZCKirQkg/pyAtVAEC6B9WFBqOte+gOTfm6ZQjdZwhmUBGB2+XiS5S2ddzoczwUz XyxiUhgm8JT4NcXfZolw43un2HQayIVDPk+L/muXIogcLMr4A9ttB6jfqvPljjNRosLc Fl0BKy3VI0Q/4jkWy3FNJmHepQDgTAMhNnfqQAKs8AfmX0bkPT7BkscOUd9AmnWmSZzN Tuvlg5+ViEHU6AVIwABE5VUFi6gLIERWWsPvLRLhbWApi1Tywf7dtixzL885EdC3tWJm znrEJfdeKRtauxg1nJhgtVy4gbzjTKge2Mw2c1BjYHWM/NbLq38/5FEPJ7f7PIkth0sJ LFTw== 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:mime-version :content-transfer-encoding; bh=eGXjfQahGJEMI3dFWEvZHra9f4CPaADa6kwDLG6Sz0U=; b=HBLrmzQZULdVRA7nLP8+IpsvB83pHR3Tqd3ElikEmvaTcR/DiKKsmXYtzg8tAr6ggE LCnjrBPzMqkb43bt1sQVQP7cp87a5huCCFNHtls+RhwA8HjPxe8Y3ncHuYuo9Ik62AtY WrNfoHe2qYQytNhoGf0Xk/POHR7mV0FjpL1i3kxD7ZIESsqjusNtM17ArFYS6iN12uW+ 9h+DC3AIdr5XRC9hx9AMghrvvniRuW8V4J89NuBFxDye/HCls3thnbruSCMrf1X0ePaO 4ODiNw5ODXg4P0rk+pLjX5DXdxk/0Ey+NCrksiPYgSTrPi43MXNKZV/RyNKCv3tW/jc3 7sPg== X-Gm-Message-State: AOAM530Un5OY66QmNTn6rUBYGJwEFZMu8/S1sfq0SxUpEw5LLwhKuPTs KYRQKk64DlcS606U2VMKI8UM3A== X-Google-Smtp-Source: ABdhPJzTlPmc4fvi8qfUEFpH90MaEppPYMQ/O0VUx6imHli5jRS7GKutNv3Wd8FBrZ35ppS9bKW62w== X-Received: by 2002:a63:db57:: with SMTP id x23mr33353040pgi.178.1594103294073; Mon, 06 Jul 2020 23:28:14 -0700 (PDT) Received: from Smcdef-MBP.local.net ([103.136.221.72]) by smtp.gmail.com with ESMTPSA id m12sm1362628pjf.17.2020.07.06.23.28.09 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Mon, 06 Jul 2020 23:28:13 -0700 (PDT) From: Muchun Song To: cl@linux.com, penberg@kernel.org, rientjes@google.com, iamjoonsoo.kim@lge.com, akpm@linux-foundation.org Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, shakeelb@google.com, Muchun Song Subject: [PATCH v5.4.y, v4.19.y] mm: memcg/slab: fix memory leak at non-root kmem_cache destroy Date: Tue, 7 Jul 2020 14:27:54 +0800 Message-Id: <20200707062754.8383-1-songmuchun@bytedance.com> X-Mailer: git-send-email 2.21.0 (Apple Git-122) MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org If the kmem_cache refcount is greater than one, we should not mark the root kmem_cache as dying. If we mark the root kmem_cache dying incorrectly, the non-root kmem_cache can never be destroyed. It resulted in memory leak when memcg was destroyed. We can use the following steps to reproduce. 1) Use kmem_cache_create() to create a new kmem_cache named A. 2) Coincidentally, the kmem_cache A is an alias for kmem_cache B, so the refcount of B is just increased. 3) Use kmem_cache_destroy() to destroy the kmem_cache A, just decrease the B's refcount but mark the B as dying. 4) Create a new memory cgroup and alloc memory from the kmem_cache A. It leads to create a non-root kmem_cache for allocating. 5) When destroy the memory cgroup created in the step 4), the non-root kmem_cache can never be destroyed. If we repeat steps 4) and 5), this will cause a lot of memory leak. So only when refcount reach zero, we mark the root kmem_cache as dying. Fixes: 92ee383f6daa ("mm: fix race between kmem_cache destroy, create and deactivate") Signed-off-by: Muchun Song --- mm/slab_common.c | 43 +++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 41 insertions(+), 2 deletions(-) diff --git a/mm/slab_common.c b/mm/slab_common.c index 8c1ffbf7de45..83ee6211aec7 100644 --- a/mm/slab_common.c +++ b/mm/slab_common.c @@ -258,6 +258,11 @@ static void memcg_unlink_cache(struct kmem_cache *s) list_del(&s->memcg_params.kmem_caches_node); } } + +static inline bool memcg_kmem_cache_dying(struct kmem_cache *s) +{ + return is_root_cache(s) && s->memcg_params.dying; +} #else static inline int init_memcg_params(struct kmem_cache *s, struct kmem_cache *root_cache) @@ -272,6 +277,11 @@ static inline void destroy_memcg_params(struct kmem_cache *s) static inline void memcg_unlink_cache(struct kmem_cache *s) { } + +static inline bool memcg_kmem_cache_dying(struct kmem_cache *s) +{ + return false; +} #endif /* CONFIG_MEMCG_KMEM */ /* @@ -326,6 +336,13 @@ int slab_unmergeable(struct kmem_cache *s) if (s->refcount < 0) return 1; + /* + * If the kmem_cache is dying. We should also skip this + * kmem_cache. + */ + if (memcg_kmem_cache_dying(s)) + return 1; + return 0; } @@ -944,8 +961,6 @@ void kmem_cache_destroy(struct kmem_cache *s) if (unlikely(!s)) return; - flush_memcg_workqueue(s); - get_online_cpus(); get_online_mems(); @@ -955,6 +970,30 @@ void kmem_cache_destroy(struct kmem_cache *s) if (s->refcount) goto out_unlock; +#ifdef CONFIG_MEMCG_KMEM + mutex_unlock(&slab_mutex); + + put_online_mems(); + put_online_cpus(); + + flush_memcg_workqueue(s); + + get_online_cpus(); + get_online_mems(); + + mutex_lock(&slab_mutex); + + if (WARN(s->refcount, + "kmem_cache_destroy %s: Slab cache is still referenced\n", + s->name)) { + /* + * Reset the dying flag setted by flush_memcg_workqueue(). + */ + s->memcg_params.dying = false; + goto out_unlock; + } +#endif + err = shutdown_memcg_caches(s); if (!err) err = shutdown_cache(s); -- 2.11.0