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=-7.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no 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 2AC7DC433E8 for ; Tue, 28 Jul 2020 15:17:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0257A2065C for ; Tue, 28 Jul 2020 15:17:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1595949431; bh=iVPJO34OY7XxYoQPxs+Z2edcN9FjEC5up2igQlk6TIM=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=Jwzn6yu1KZeEzWTQPC/xsCwwUi031pqE4lya10f0ZX476I1TNAG5T7sSnM+QfZJAP kagAI/L0VOkw6Q05PlexGw4nx5oLAtD1u3rnZMA6FFPt9AukoZKB9JfrILmgUGFkXj 64YLj/NOZfadbAutVtUDEhHLD/C0Lfn/mXrwTdVw= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730776AbgG1PRJ (ORCPT ); Tue, 28 Jul 2020 11:17:09 -0400 Received: from mail.kernel.org ([198.145.29.99]:40324 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730640AbgG1PRF (ORCPT ); Tue, 28 Jul 2020 11:17:05 -0400 Received: from localhost (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id BB27E2065C; Tue, 28 Jul 2020 15:17:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1595949425; bh=iVPJO34OY7XxYoQPxs+Z2edcN9FjEC5up2igQlk6TIM=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=NOxKdbdNitc7pl98MAMaeiLTMttCJXbZp9OwbzyaxJYI3eFKSMuDtZ32BHx+CTFqK 1Cm7V3LhiqjwC/mAohk+7QWpCTjjfdMDeCF0PehwKh4RaVYe+DWpAll9nMNtR9IPBr Xvwk3KNu3qPVpPNgFjp6ahyyAD7fkf/Qp2OLzVh8= Date: Tue, 28 Jul 2020 11:17:03 -0400 From: Sasha Levin To: Muchun Song Cc: Greg Kroah-Hartman , LKML , stable@vger.kernel.org, Andrew Morton , Shakeel Butt , Roman Gushchin , Vlastimil Babka , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Linus Torvalds Subject: Re: [External] [PATCH 4.19 76/86] mm: memcg/slab: fix memory leak at non-root kmem_cache destroy Message-ID: <20200728151703.GM406581@sasha-vm> References: <20200727134914.312934924@linuxfoundation.org> <20200727134918.205538211@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jul 28, 2020 at 08:56:41PM +0800, Muchun Song wrote: >On Mon, Jul 27, 2020 at 10:12 PM Greg Kroah-Hartman > wrote: >> >> From: Muchun Song >> >> commit d38a2b7a9c939e6d7329ab92b96559ccebf7b135 upstream. >> >> 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 >> B. It leads to create a non-root kmem_cache for allocating memory. >> 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 >> Signed-off-by: Andrew Morton >> Reviewed-by: Shakeel Butt >> Acked-by: Roman Gushchin >> Cc: Vlastimil Babka >> Cc: Christoph Lameter >> Cc: Pekka Enberg >> Cc: David Rientjes >> Cc: Joonsoo Kim >> Cc: Shakeel Butt >> Cc: >> Link: http://lkml.kernel.org/r/20200716165103.83462-1-songmuchun@bytedance.com >> Signed-off-by: Linus Torvalds >> Signed-off-by: Greg Kroah-Hartman >> >> --- >> mm/slab_common.c | 35 ++++++++++++++++++++++++++++------- >> 1 file changed, 28 insertions(+), 7 deletions(-) >> >> --- a/mm/slab_common.c >> +++ b/mm/slab_common.c >> @@ -310,6 +310,14 @@ int slab_unmergeable(struct kmem_cache * >> if (s->refcount < 0) >> return 1; >> >> +#ifdef CONFIG_MEMCG_KMEM >> + /* >> + * Skip the dying kmem_cache. >> + */ >> + if (s->memcg_params.dying) >> + return 1; >> +#endif >> + >> return 0; >> } >> >> @@ -832,12 +840,15 @@ static int shutdown_memcg_caches(struct >> return 0; >> } >> >> -static void flush_memcg_workqueue(struct kmem_cache *s) >> +static void memcg_set_kmem_cache_dying(struct kmem_cache *s) >> { >> mutex_lock(&slab_mutex); >> s->memcg_params.dying = true; >> mutex_unlock(&slab_mutex); > >We should remove mutex_lock/unlock(&slab_mutex) here, because >we already hold the slab_mutex from kmem_cache_destroy(). Good catch! I backported 63b02ef7dc4e ("mm: memcg/slab: synchronize access to kmem_cache dying flag using a spinlock") instead of changing this patch. -- Thanks, Sasha