From nobody Tue Feb 10 01:50:23 2026 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 5BB1CC7EE22 for ; Mon, 15 May 2023 13:39:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242140AbjEONje (ORCPT ); Mon, 15 May 2023 09:39:34 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51850 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241839AbjEONj3 (ORCPT ); Mon, 15 May 2023 09:39:29 -0400 Received: from szxga08-in.huawei.com (szxga08-in.huawei.com [45.249.212.255]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7F5791BC; Mon, 15 May 2023 06:39:28 -0700 (PDT) Received: from kwepemm600013.china.huawei.com (unknown [172.30.72.55]) by szxga08-in.huawei.com (SkyGuard) with ESMTP id 4QKgNB2K5Gz18LY7; Mon, 15 May 2023 21:35:06 +0800 (CST) Received: from huawei.com (10.175.104.67) 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 15.1.2507.23; Mon, 15 May 2023 21:39:23 +0800 From: Zhihao Cheng To: , , CC: , , Subject: [PATCH v2 2/2] ovl: get_acl: Fix null pointer dereference at realinode in rcu-walk mode Date: Mon, 15 May 2023 21:36:29 +0800 Message-ID: <20230515133629.1974610-3-chengzhihao1@huawei.com> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20230515133629.1974610-1-chengzhihao1@huawei.com> References: <20230515133629.1974610-1-chengzhihao1@huawei.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Originating-IP: [10.175.104.67] X-ClientProxiedBy: dggems703-chm.china.huawei.com (10.3.19.180) To kwepemm600013.china.huawei.com (7.193.23.68) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" 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 =3D 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 =3D NULL ovl_inode_upper upperdentry =3D 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]. Fix it by using helper ovl_i_path_realinode() to get realpath and real inode after non-nullptr checking. Link: https://bugzilla.kernel.org/show_bug.cgi?id=3D217404 Fixes: 332f606b32b6 ("ovl: enable RCU'd ->get_acl()") Signed-off-by: Zhihao Cheng Suggested-by: Christian Brauner --- fs/overlayfs/inode.c | 14 ++++++-------- 1 file changed, 6 insertions(+), 8 deletions(-) diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c index cc3ef5a6666a..b2021eada8be 100644 --- a/fs/overlayfs/inode.c +++ b/fs/overlayfs/inode.c @@ -576,20 +576,18 @@ struct posix_acl *do_ovl_get_acl(struct mnt_idmap *id= map, struct inode *inode, int type, bool rcu, bool noperm) { - struct inode *realinode =3D ovl_inode_real(inode); + struct inode *realinode; struct posix_acl *acl; struct path realpath; + int err; + + err =3D ovl_i_path_realinode(inode, &realpath, &realinode, rcu); + if (err) + return ERR_PTR(err); =20 if (!IS_POSIXACL(realinode)) return NULL; =20 - /* Careful in RCU walk mode */ - ovl_i_path_real(inode, &realpath); - if (!realpath.dentry) { - WARN_ON(!rcu); - return ERR_PTR(-ECHILD); - } - if (rcu) { /* * If the layer is idmapped drop out of RCU path walk --=20 2.39.2