From nobody Mon Feb 9 09:08:45 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 193BDEB64DC for ; Mon, 10 Jul 2023 03:31:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230389AbjGJDb4 (ORCPT ); Sun, 9 Jul 2023 23:31:56 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33416 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229641AbjGJDba (ORCPT ); Sun, 9 Jul 2023 23:31:30 -0400 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 791E62119; Sun, 9 Jul 2023 20:29:13 -0700 (PDT) Received: from kwepemm600013.china.huawei.com (unknown [172.30.72.55]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4QzqFn2QNTzTm20; Mon, 10 Jul 2023 11:27:57 +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 15.1.2507.27; Mon, 10 Jul 2023 11:29:06 +0800 From: Zhihao Cheng To: , CC: , , , , , Subject: [PATCH 5.15] ovl: fix null pointer dereference in ovl_get_acl_rcu() Date: Mon, 10 Jul 2023 11:27:30 +0800 Message-ID: <20230710032730.2049748-1-chengzhihao1@huawei.com> X-Mailer: git-send-email 2.39.2 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Originating-IP: [10.175.104.67] X-ClientProxiedBy: dggems705-chm.china.huawei.com (10.3.19.182) 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" [ 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 =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]. 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. Link: https://bugzilla.kernel.org/show_bug.cgi?id=3D217404 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; =20 - 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; =20 if (rcu) --=20 2.39.2