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=-19.1 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1,USER_IN_DEF_DKIM_WL 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 42BABC433DF for ; Tue, 28 Jul 2020 19:46:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1F109207F5 for ; Tue, 28 Jul 2020 19:46:11 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="g0MbWG+Z" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732969AbgG1TqJ (ORCPT ); Tue, 28 Jul 2020 15:46:09 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56542 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732958AbgG1TqJ (ORCPT ); Tue, 28 Jul 2020 15:46:09 -0400 Received: from mail-pj1-x1043.google.com (mail-pj1-x1043.google.com [IPv6:2607:f8b0:4864:20::1043]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 466D2C061794 for ; Tue, 28 Jul 2020 12:46:09 -0700 (PDT) Received: by mail-pj1-x1043.google.com with SMTP id t15so535674pjq.5 for ; Tue, 28 Jul 2020 12:46:09 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:from:to:cc:subject:in-reply-to:message-id:references :user-agent:mime-version; bh=CcfvoFL7aJEulqwwTYjAtmM4mTbUznShrvhOhRcbiJ4=; b=g0MbWG+Z2VyMhmBmNaSfj94wMWmzF14QrIOiZbbusdMfkMpd2OYfLufJvgWBm6laan AWvEJUjSK/+ZaYwgkGS69i2l4BsvcmJe6fkS8OzN9v+Csv34WY6lba6pDhFSwOjjqAQm jpAE6od3r/7yj6oPlqsnVvjzqn96hPkJgnLXha614YEX+93fh8uaAHIwuGuQUhkNsZjo yeyAbwSxrvg1nVfQPs6jrTiNVINtSdGVna6TARs2fRt/UoBEGDIUqmz4odIKXVK0FrLq nyriSswCPQumzxAFtokW6BVp8Eu5HH4wzurRuFAyau4bwZBVEbltwHPG/SqNvRMV3yKW en9A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:in-reply-to:message-id :references:user-agent:mime-version; bh=CcfvoFL7aJEulqwwTYjAtmM4mTbUznShrvhOhRcbiJ4=; b=UvY906XSOkLqjRbxK6VaUd5TfcXZHWXjs2eK440gGewKFPsc4y6EvnZ6oVClqtxfW4 g7GnwMRmP94FlLPyPWCqdrYVUr1jPRfY5R+RJuajxjI4sTKEaW9j5X4cFUQ6BdCtEgpl 2lync/DUOemFBN59PooVe6Je7rO5pSdLZkOgaRkmXo2R1i2IwLcbwjr73p71ip09IMeJ Hy3vTH6NTe7zxJyZ7bcO12gAMN2NFUD2F4em78kvl0CUkGiuDeN+dxODJeTjP42CxS0w o860LgRP+Pj6Zpg1iCiHgt3B11p44q3gxT5MI0PF2xVOsqYpTRVHnOlHeFOafCmA3Wp8 fSWw== X-Gm-Message-State: AOAM531L5l1/UIV7oeVIaQdGWVBG70NsVa+yGkDM4QrcqY8/hz359ZsH SGVySGhhi/r3LkqjPUrG9sVXVA== X-Google-Smtp-Source: ABdhPJxpt5JQVmgBPnYf4Y4KhQFY8WRyAIyKEPvlPItSlrgq906zB6TAsovA0eaDTxxBPgXCQO5elA== X-Received: by 2002:a17:90a:3e02:: with SMTP id j2mr6283098pjc.47.1595965568586; Tue, 28 Jul 2020 12:46:08 -0700 (PDT) Received: from [2620:15c:17:3:4a0f:cfff:fe51:6667] ([2620:15c:17:3:4a0f:cfff:fe51:6667]) by smtp.gmail.com with ESMTPSA id z9sm9533146pfn.59.2020.07.28.12.46.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 28 Jul 2020 12:46:08 -0700 (PDT) Date: Tue, 28 Jul 2020 12:46:07 -0700 (PDT) From: David Rientjes X-X-Sender: rientjes@chino.kir.corp.google.com To: qiang.zhang@windriver.com cc: cl@linux.com, penberg@kernel.org, iamjoonsoo.kim@lge.com, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/slab.c: add node spinlock protect in __cache_free_alien In-Reply-To: <20200728095551.30634-1-qiang.zhang@windriver.com> Message-ID: References: <20200728095551.30634-1-qiang.zhang@windriver.com> User-Agent: Alpine 2.23 (DEB 453 2020-06-18) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 28 Jul 2020, qiang.zhang@windriver.com wrote: > From: Zhang Qiang > > We should add node spinlock protect "n->alien" which may be > assigned to NULL in cpuup_canceled func. cause address access > exception. > Hi, do you have an example NULL pointer dereference where you have hit this? This rather looks like something to fix up in cpuup_canceled() since it's currently manipulating the alien cache for the canceled cpu's node. > Fixes: 18bf854117c6 ("slab: use get_node() and kmem_cache_node() functions") > Signed-off-by: Zhang Qiang > --- > mm/slab.c | 7 +++++-- > 1 file changed, 5 insertions(+), 2 deletions(-) > > diff --git a/mm/slab.c b/mm/slab.c > index a89633603b2d..290523c90b4e 100644 > --- a/mm/slab.c > +++ b/mm/slab.c > @@ -759,8 +759,10 @@ static int __cache_free_alien(struct kmem_cache *cachep, void *objp, > > n = get_node(cachep, node); > STATS_INC_NODEFREES(cachep); > + spin_lock(&n->list_lock); > if (n->alien && n->alien[page_node]) { > alien = n->alien[page_node]; > + spin_unlock(&n->list_lock); > ac = &alien->ac; > spin_lock(&alien->lock); > if (unlikely(ac->avail == ac->limit)) { > @@ -769,14 +771,15 @@ static int __cache_free_alien(struct kmem_cache *cachep, void *objp, > } > ac->entry[ac->avail++] = objp; > spin_unlock(&alien->lock); > - slabs_destroy(cachep, &list); > } else { > + spin_unlock(&n->list_lock); > n = get_node(cachep, page_node); > spin_lock(&n->list_lock); > free_block(cachep, &objp, 1, page_node, &list); > spin_unlock(&n->list_lock); > - slabs_destroy(cachep, &list); > } > + > + slabs_destroy(cachep, &list); > return 1; > } > > -- > 2.26.2 > > 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=-19.1 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1,USER_IN_DEF_DKIM_WL 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 9C0BAC433E0 for ; Tue, 28 Jul 2020 19:46:11 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 58198207F5 for ; 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Tue, 28 Jul 2020 12:46:08 -0700 (PDT) Date: Tue, 28 Jul 2020 12:46:07 -0700 (PDT) From: David Rientjes X-X-Sender: rientjes@chino.kir.corp.google.com To: qiang.zhang@windriver.com cc: cl@linux.com, penberg@kernel.org, iamjoonsoo.kim@lge.com, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/slab.c: add node spinlock protect in __cache_free_alien In-Reply-To: <20200728095551.30634-1-qiang.zhang@windriver.com> Message-ID: References: <20200728095551.30634-1-qiang.zhang@windriver.com> User-Agent: Alpine 2.23 (DEB 453 2020-06-18) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Rspamd-Queue-Id: 4FA1318140B75 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam05 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 Tue, 28 Jul 2020, qiang.zhang@windriver.com wrote: > From: Zhang Qiang > > We should add node spinlock protect "n->alien" which may be > assigned to NULL in cpuup_canceled func. cause address access > exception. > Hi, do you have an example NULL pointer dereference where you have hit this? This rather looks like something to fix up in cpuup_canceled() since it's currently manipulating the alien cache for the canceled cpu's node. > Fixes: 18bf854117c6 ("slab: use get_node() and kmem_cache_node() functions") > Signed-off-by: Zhang Qiang > --- > mm/slab.c | 7 +++++-- > 1 file changed, 5 insertions(+), 2 deletions(-) > > diff --git a/mm/slab.c b/mm/slab.c > index a89633603b2d..290523c90b4e 100644 > --- a/mm/slab.c > +++ b/mm/slab.c > @@ -759,8 +759,10 @@ static int __cache_free_alien(struct kmem_cache *cachep, void *objp, > > n = get_node(cachep, node); > STATS_INC_NODEFREES(cachep); > + spin_lock(&n->list_lock); > if (n->alien && n->alien[page_node]) { > alien = n->alien[page_node]; > + spin_unlock(&n->list_lock); > ac = &alien->ac; > spin_lock(&alien->lock); > if (unlikely(ac->avail == ac->limit)) { > @@ -769,14 +771,15 @@ static int __cache_free_alien(struct kmem_cache *cachep, void *objp, > } > ac->entry[ac->avail++] = objp; > spin_unlock(&alien->lock); > - slabs_destroy(cachep, &list); > } else { > + spin_unlock(&n->list_lock); > n = get_node(cachep, page_node); > spin_lock(&n->list_lock); > free_block(cachep, &objp, 1, page_node, &list); > spin_unlock(&n->list_lock); > - slabs_destroy(cachep, &list); > } > + > + slabs_destroy(cachep, &list); > return 1; > } > > -- > 2.26.2 > >