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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 191A0CCA47C for ; Wed, 6 Jul 2022 07:08:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231521AbiGFHIQ (ORCPT ); Wed, 6 Jul 2022 03:08:16 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34352 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231150AbiGFHIN (ORCPT ); Wed, 6 Jul 2022 03:08:13 -0400 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6AAFCD5A; Wed, 6 Jul 2022 00:08:12 -0700 (PDT) Received: from dggpemm500024.china.huawei.com (unknown [172.30.72.55]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4Ld9Yw0X2JzkX5l; Wed, 6 Jul 2022 15:06:12 +0800 (CST) Received: from dggpemm100009.china.huawei.com (7.185.36.113) by dggpemm500024.china.huawei.com (7.185.36.203) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Wed, 6 Jul 2022 15:07:32 +0800 Received: from [10.174.179.24] (10.174.179.24) by dggpemm100009.china.huawei.com (7.185.36.113) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Wed, 6 Jul 2022 15:07:32 +0800 Subject: Re: [PATCH 5.15 v2] mm/filemap: fix UAF in find_lock_entries To: Greg Kroah-Hartman , Andrew Morton , Matthew Wilcox , Jan Kara , William Kucharski , "Christoph Hellwig" References: <20220706073045.1398379-1-liushixin2@huawei.com> CC: , From: Liu Shixin Message-ID: <904d2d5a-c39a-928e-55f2-58d1c1fa737e@huawei.com> Date: Wed, 6 Jul 2022 15:07:32 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.7.1 MIME-Version: 1.0 In-Reply-To: <20220706073045.1398379-1-liushixin2@huawei.com> Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.179.24] X-ClientProxiedBy: dggems703-chm.china.huawei.com (10.3.19.180) To dggpemm100009.china.huawei.com (7.185.36.113) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This patch has a compilation problem, please ignore it. On 2022/7/6 15:30, Liu Shixin wrote: > Release refcount after xas_set to fix UAF which may cause panic like this: > > page:ffffea000491fa40 refcount:1 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x1247e9 > head:ffffea000491fa00 order:3 compound_mapcount:0 compound_pincount:0 > memcg:ffff888104f91091 > flags: 0x2fffff80010200(slab|head|node=0|zone=2|lastcpupid=0x1fffff) > ... > page dumped because: VM_BUG_ON_PAGE(PageTail(page)) > ------------[ cut here ]------------ > kernel BUG at include/linux/page-flags.h:632! > invalid opcode: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN > CPU: 1 PID: 7642 Comm: sh Not tainted 5.15.51-dirty #26 > ... > Call Trace: > > __invalidate_mapping_pages+0xe7/0x540 > drop_pagecache_sb+0x159/0x320 > iterate_supers+0x120/0x240 > drop_caches_sysctl_handler+0xaa/0xe0 > proc_sys_call_handler+0x2b4/0x480 > new_sync_write+0x3d6/0x5c0 > vfs_write+0x446/0x7a0 > ksys_write+0x105/0x210 > do_syscall_64+0x35/0x80 > entry_SYSCALL_64_after_hwframe+0x44/0xae > RIP: 0033:0x7f52b5733130 > ... > > This problem has been fixed on mainline by patch 6b24ca4a1a8d ("mm: Use > multi-index entries in the page cache") since it deletes the related code. > > Fixes: 5c211ba29deb ("mm: add and use find_lock_entries") > Signed-off-by: Liu Shixin > --- > mm/filemap.c | 10 ++++++---- > 1 file changed, 6 insertions(+), 4 deletions(-) > > diff --git a/mm/filemap.c b/mm/filemap.c > index 00e391e75880..2c65dd314c49 100644 > --- a/mm/filemap.c > +++ b/mm/filemap.c > @@ -2090,7 +2090,11 @@ unsigned find_lock_entries(struct address_space *mapping, pgoff_t start, > > rcu_read_lock(); > while ((page = find_get_entry(&xas, end, XA_PRESENT))) { > + unsigned long next_idx = xas.xa_index; > + > if (!xa_is_value(page)) { > + if (PageTransHuge(page)) > + next_idx = page->index + thp_nr_pages(page); > if (page->index < start) > goto put; > if (page->index + thp_nr_pages(page) - 1 > end) > @@ -2111,11 +2115,9 @@ unsigned find_lock_entries(struct address_space *mapping, pgoff_t start, > put: > put_page(page); > next: > - if (!xa_is_value(page) && PageTransHuge(page)) { > - unsigned int nr_pages = thp_nr_pages(page); > - > + if (next_idx != xas.xa_index) { > /* Final THP may cross MAX_LFS_FILESIZE on 32-bit */ > - xas_set(&xas, page->index + nr_pages); > + xas_set(&xas, next_idx); > if (xas.xa_index < nr_pages) > break; > }