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 3C7BDEB64DD for ; Mon, 17 Jul 2023 03:15:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230352AbjGQDPK (ORCPT ); Sun, 16 Jul 2023 23:15:10 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38638 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231262AbjGQDOs (ORCPT ); Sun, 16 Jul 2023 23:14:48 -0400 Received: from szxga08-in.huawei.com (szxga08-in.huawei.com [45.249.212.255]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 129DEE46; Sun, 16 Jul 2023 20:13:55 -0700 (PDT) Received: from kwepemm600013.china.huawei.com (unknown [172.30.72.57]) by szxga08-in.huawei.com (SkyGuard) with ESMTP id 4R46bX3ndFz18LfQ; Mon, 17 Jul 2023 11:13:12 +0800 (CST) Received: from [10.174.178.46] (10.174.178.46) by kwepemm600013.china.huawei.com (7.193.23.68) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.27; Mon, 17 Jul 2023 11:13:52 +0800 Subject: Re: [PATCH 5.15] ovl: fix null pointer dereference in ovl_get_acl_rcu() To: Amir Goldstein CC: , , , , , References: <20230710032730.2049748-1-chengzhihao1@huawei.com> From: Zhihao Cheng Message-ID: <901c2673-b91b-5a06-35e7-5b353a42ed71@huawei.com> Date: Mon, 17 Jul 2023 11:13:51 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.178.46] X-ClientProxiedBy: dggems706-chm.china.huawei.com (10.3.19.183) To kwepemm600013.china.huawei.com (7.193.23.68) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-unionfs@vger.kernel.org 在 2023/7/17 2:26, Amir Goldstein 写道: > On Mon, Jul 10, 2023 at 6:29 AM Zhihao Cheng wrote: >> >> [ Upstream commit f4e19e595cc2e76a8a58413eb19d3d9c51328b53 ] >> >> Following process: >> P1 P2 >> path_openat >> link_path_walk >> may_lookup >> inode_permission(rcu) >> ovl_permission >> acl_permission_check >> check_acl >> get_cached_acl_rcu >> ovl_get_inode_acl >> realinode = ovl_inode_real(ovl_inode) >> drop_cache >> __dentry_kill(ovl_dentry) >> iput(ovl_inode) >> ovl_destroy_inode(ovl_inode) >> dput(oi->__upperdentry) >> dentry_kill(upperdentry) >> dentry_unlink_inode >> upperdentry->d_inode = NULL >> ovl_inode_upper >> upperdentry = ovl_i_dentry_upper(ovl_inode) >> d_inode(upperdentry) // returns NULL >> IS_POSIXACL(realinode) // NULL pointer dereference >> , will trigger an null pointer dereference at realinode: >> [ 205.472797] BUG: kernel NULL pointer dereference, address: >> 0000000000000028 >> [ 205.476701] CPU: 2 PID: 2713 Comm: ls Not tainted >> 6.3.0-12064-g2edfa098e750-dirty #1216 >> [ 205.478754] RIP: 0010:do_ovl_get_acl+0x5d/0x300 >> [ 205.489584] Call Trace: >> [ 205.489812] >> [ 205.490014] ovl_get_inode_acl+0x26/0x30 >> [ 205.490466] get_cached_acl_rcu+0x61/0xa0 >> [ 205.490908] generic_permission+0x1bf/0x4e0 >> [ 205.491447] ovl_permission+0x79/0x1b0 >> [ 205.491917] inode_permission+0x15e/0x2c0 >> [ 205.492425] link_path_walk+0x115/0x550 >> [ 205.493311] path_lookupat.isra.0+0xb2/0x200 >> [ 205.493803] filename_lookup+0xda/0x240 >> [ 205.495747] vfs_fstatat+0x7b/0xb0 >> >> Fetch a reproducer in [Link]. >> >> Use the helper ovl_i_path_realinode() to get realinode and then do >> non-nullptr checking. >> >> There are some changes from upstream commit: >> 1. Corrusponds to do_ovl_get_acl() in 5.15 is ovl_get_acl() >> 2. ovl_i_path_real is not imported in 5.15, we can get realinode by >> ovl_inode_real >> 3. CONFIG_FS_POSIX_ACL checking is dropped in commit >> ded536561a3674327dfa4bb389085705cae22b8a ("ovl: improve ovl_get_acl() >> if POSIX ACL support is off"), we still keep it in 5.15. > > Zhihao, > > Can you please provide also the backport for 6.1. > Sure, I sent it out, please refer to https://lore.kernel.org/stable/20230717030904.1669754-1-chengzhihao1@huawei.com/T/#t. > Basically, the same as this one without the CONFIG_FS_POSIX_ACL check. > > Thanks, > Amir. > >> >> Link: https://bugzilla.kernel.org/show_bug.cgi?id=217404 >> Fixes: 332f606b32b6 ("ovl: enable RCU'd ->get_acl()") >> Cc: # v5.15 >> Signed-off-by: Zhihao Cheng >> Suggested-by: Christian Brauner >> Suggested-by: Amir Goldstein >> Signed-off-by: Amir Goldstein >> Signed-off-by: Miklos Szeredi >> --- >> fs/overlayfs/inode.c | 10 +++++++++- >> 1 file changed, 9 insertions(+), 1 deletion(-) >> >> diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c >> index d41f0c8e0e2a..65e5e6eb761a 100644 >> --- a/fs/overlayfs/inode.c >> +++ b/fs/overlayfs/inode.c >> @@ -453,7 +453,15 @@ struct posix_acl *ovl_get_acl(struct inode *inode, int type, bool rcu) >> const struct cred *old_cred; >> struct posix_acl *acl; >> >> - if (!IS_ENABLED(CONFIG_FS_POSIX_ACL) || !IS_POSIXACL(realinode)) >> + if (!IS_ENABLED(CONFIG_FS_POSIX_ACL)) >> + return NULL; >> + >> + if (!realinode) { >> + WARN_ON(!rcu); >> + return ERR_PTR(-ECHILD); >> + } >> + >> + if (!IS_POSIXACL(realinode)) >> return NULL; >> >> if (rcu) >> -- >> 2.39.2 >> > . >