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=-11.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=ham 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 6E486C433DF for ; Wed, 19 Aug 2020 20:26:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 410412083B for ; Wed, 19 Aug 2020 20:26:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1597868794; bh=9mkNXL3qxuTKmxf4J9KypFPk3CQwCYHT9w9PsOO+DTM=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=g+1urxl2zKJAa/FqicQizQrSJWgW4V8ZWweyoaL5B+Ce6H1pCNh4h6OuTtMdC2y2H i63IDZzf6EyyKeg1K8wtpZFjGHYFwYfHtPcnRTKGK1zoyxMxSYqwoBYOnIxvLOIfgg +bSqdMZ8sx6MFeo8XMLE62HFy7XpucEpw3JdYviY= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726792AbgHSU0d (ORCPT ); Wed, 19 Aug 2020 16:26:33 -0400 Received: from mail.kernel.org ([198.145.29.99]:40320 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725275AbgHSU0c (ORCPT ); Wed, 19 Aug 2020 16:26:32 -0400 Received: from localhost.localdomain (c-73-231-172-41.hsd1.ca.comcast.net [73.231.172.41]) (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 49112207DE; Wed, 19 Aug 2020 20:26:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1597868791; bh=9mkNXL3qxuTKmxf4J9KypFPk3CQwCYHT9w9PsOO+DTM=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=ogYz+tB2oT7tA+9+9cnWc0TnEfTegSQY3aCypno2mo++dWppK7qqJSAw1qmjEY0fA gby5Hv9Exyh40ojcVXRd+vUpDXN9AWm3/mWRSnuR5OCt5H9ZE7HO4l2VLx7ybDhVn9 Hn81oKCfhqOGfTdVFm6UqD6+VZyLL49dfGhqynoY= Date: Wed, 19 Aug 2020 13:26:30 -0700 From: Andrew Morton To: kpark3469@gmail.com Cc: linux-kernel@vger.kernel.org, cl@linux.com, penberg@kernel.org, rientjes@google.com, iamjoonsoo.kim@lge.com, keun-o.park@digital14.com, linux-mm@kvack.org, Thomas Garnier Subject: Re: [PATCH] mm: slub: re-initialize randomized freelist sequence in calculate_sizes Message-Id: <20200819132630.7b26964cc8946189ab5b1a70@linux-foundation.org> In-Reply-To: <20200808095030.13368-1-kpark3469@gmail.com> References: <20200808095030.13368-1-kpark3469@gmail.com> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.31; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org (cc Thomas and linux-mm) On Sat, 8 Aug 2020 13:50:30 +0400 kpark3469@gmail.com wrote: > From: Sahara > > Slab cache flags are exported to sysfs and are allowed to get modified > from userspace. Some of those may call calculate_sizes function because > the changed flag can take an effect on slab object size and layout, > which means kmem_cache may have different order and objects. > The freelist pointer corruption occurs if some slab flags are modified > while CONFIG_SLAB_FREELIST_RANDOM is turned on. > > $ echo 0 > /sys/kernel/slab/zs_handle/store_user > $ echo 0 > /sys/kernel/slab/zspage/store_user > $ mkswap /dev/block/zram0 > $ swapon /dev/block/zram0 -p 32758 > > ============================================================================= > BUG zs_handle (Not tainted): Freepointer corrupt > ----------------------------------------------------------------------------- > > Disabling lock debugging due to kernel taint > INFO: Slab 0xffffffbf29603600 objects=102 used=102 fp=0x0000000000000000 flags=0x0200 > INFO: Object 0xffffffca580d8d78 @offset=3448 fp=0xffffffca580d8ed0 > > Redzone 00000000f3cddd6c: bb bb bb bb bb bb bb bb ........ > Object 0000000082d5d74e: 6b 6b 6b 6b 6b 6b 6b a5 kkkkkkk. > Redzone 000000008fd80359: bb bb bb bb bb bb bb bb ........ > Padding 00000000c7f56047: 5a 5a 5a 5a 5a 5a 5a 5a ZZZZZZZZ > > In this example, an Android device tries to use zram as a swap and to > turn off store_user in order to reduce the slub object size. > When calculate_sizes is called in kmem_cache_open, size, order and > objects for zs_handle is: > size:360, order:0, objects:22 > However, if the SLAB_STORE_USER bit is cleared in store_user_store: > size: 56, order:1, objects:73 > > All the size, order, and objects is changed by calculate_sizes(), but > the size of the random_seq array is still old value(22). As a result, > out-of-bound array access can occur at shuffle_freelist() when slab > allocation is requested. > > This patch fixes the problem by re-allocating the random_seq array > with re-calculated correct objects value. > > Fixes: 210e7a43fa905 ("mm: SLUB freelist randomization") > Reported-by: Ari-Pekka Verta > Reported-by: Timo Simola > Signed-off-by: Sahara > --- > mm/slub.c | 23 ++++++++++++++++------- > 1 file changed, 16 insertions(+), 7 deletions(-) > > diff --git a/mm/slub.c b/mm/slub.c > index f226d66408ee..be1e4d6682b8 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -3704,7 +3704,22 @@ static int calculate_sizes(struct kmem_cache *s, int forced_order) > if (oo_objects(s->oo) > oo_objects(s->max)) > s->max = s->oo; > > - return !!oo_objects(s->oo); > + if (!oo_objects(s->oo)) > + return 0; > + > + /* > + * Initialize the pre-computed randomized freelist if slab is up. > + * If the randomized freelist random_seq is already initialized, > + * free and re-initialize it with re-calculated value. > + */ > + if (slab_state >= UP) { > + if (s->random_seq) > + cache_random_seq_destroy(s); > + if (init_cache_random_seq(s)) > + return 0; > + } > + > + return 1; > } > > static int kmem_cache_open(struct kmem_cache *s, slab_flags_t flags) > @@ -3748,12 +3763,6 @@ static int kmem_cache_open(struct kmem_cache *s, slab_flags_t flags) > s->remote_node_defrag_ratio = 1000; > #endif > > - /* Initialize the pre-computed randomized freelist if slab is up */ > - if (slab_state >= UP) { > - if (init_cache_random_seq(s)) > - goto error; > - } > - > if (!init_kmem_cache_nodes(s)) > goto error; > > -- > 2.17.1