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Biederman" , Sasha Levin Subject: [PATCH AUTOSEL for 4.9 188/219] userns: Don't fail follow_automount based on s_user_ns Thread-Topic: [PATCH AUTOSEL for 4.9 188/219] userns: Don't fail follow_automount based on s_user_ns Thread-Index: AQHTsz8iVft5viAKo0uMUzdqavCXgw== Date: Sat, 3 Mar 2018 22:29:46 +0000 Message-ID: <20180303222716.26640-188-alexander.levin@microsoft.com> References: <20180303222716.26640-1-alexander.levin@microsoft.com> In-Reply-To: <20180303222716.26640-1-alexander.levin@microsoft.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [52.168.54.252] x-ms-publictraffictype: Email x-microsoft-exchange-diagnostics: 1;MW2PR2101MB1020;7:W7HiJB+viiqFUcF/II2Fm/EclyRItL9LzE1+Xh/zKaOS6or1XQO89/sNsfPZeEe2cz//sNx734zthl9ebW6/oS85aR8bMAgameDqJmFMLpct1MgpZgcFDhpDCWLGllUBJixQSS/RKHw7HMiRNN+YH0+4KbxTd4WOgiMl+zc0FO1Rve5jkWrJUMd4Gk4CJtpnjEmhTLPy6sVzd7daZ2e07Cwf6NO53D74873RQcBJ9r+/PMP6mitkR+2UFIXpivHS x-ms-office365-filtering-ht: Tenant x-ms-office365-filtering-correlation-id: b687e980-4c14-4766-ff5b-08d581573d65 x-microsoft-antispam: UriScan:;BCL:0;PCL:0;RULEID:(7020095)(4652020)(48565401081)(5600026)(4604075)(3008032)(4534165)(4627221)(201703031133081)(201702281549075)(2017052603307)(7193020);SRVR:MW2PR2101MB1020; x-ms-traffictypediagnostic: MW2PR2101MB1020: authentication-results: spf=none (sender IP is ) smtp.mailfrom=Alexander.Levin@microsoft.com; x-microsoft-antispam-prvs: x-exchange-antispam-report-test: UriScan:(28532068793085)(89211679590171)(192374486261705); x-exchange-antispam-report-cfa-test: BCL:0;PCL:0;RULEID:(8211001083)(61425038)(6040501)(2401047)(8121501046)(5005006)(93006095)(93001095)(10201501046)(3231220)(944501244)(52105095)(3002001)(6055026)(61426038)(61427038)(6041288)(20161123562045)(20161123558120)(20161123564045)(20161123560045)(201703131423095)(201702281528075)(20161123555045)(201703061421075)(201703061406153)(6072148)(201708071742011);SRVR:MW2PR2101MB1020;BCL:0;PCL:0;RULEID:;SRVR:MW2PR2101MB1020; x-forefront-prvs: 0600F93FE1 x-forefront-antispam-report: SFV:NSPM;SFS:(10019020)(39380400002)(396003)(366004)(346002)(376002)(39860400002)(199004)(189003)(6436002)(5250100002)(99286004)(3846002)(6116002)(8936002)(22452003)(86612001)(86362001)(4326008)(10090500001)(68736007)(6512007)(7736002)(97736004)(25786009)(76176011)(1076002)(6486002)(2501003)(66066001)(36756003)(107886003)(2950100002)(8676002)(305945005)(5660300001)(105586002)(53936002)(3280700002)(81166006)(6506007)(106356001)(2906002)(81156014)(316002)(478600001)(72206003)(10290500003)(2900100001)(54906003)(110136005)(59450400001)(186003)(102836004)(26005)(14454004)(3660700001)(22906009)(217873001);DIR:OUT;SFP:1102;SCL:1;SRVR:MW2PR2101MB1020;H:MW2PR2101MB1034.namprd21.prod.outlook.com;FPR:;SPF:None;PTR:InfoNoRecords;A:1;MX:1;LANG:en; x-microsoft-antispam-message-info: CB7JJm/tVUp0ljAlN0u/h5Z1RENTFY9wm87horqlMISkmsNfI7v3cFn3YPmCz5TiNEe5dstnpovAqV53ZT8KR3DiJnIYvZOm+Rdbc0QYNZHrRfpSa/H9A6oLFEaR5P+YBVR5r9Vj5IBhCqX7Ht8tPpc+ruR2UbEACkmzTkc7nAk= spamdiagnosticoutput: 1:99 spamdiagnosticmetadata: NSPM Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: microsoft.com X-MS-Exchange-CrossTenant-Network-Message-Id: b687e980-4c14-4766-ff5b-08d581573d65 X-MS-Exchange-CrossTenant-originalarrivaltime: 03 Mar 2018 22:29:46.4476 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 72f988bf-86f1-41af-91ab-2d7cd011db47 X-MS-Exchange-Transport-CrossTenantHeadersStamped: MW2PR2101MB1020 Sender: stable-owner@vger.kernel.org X-Mailing-List: stable@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: From: "Eric W. Biederman" [ Upstream commit bbc3e471011417598e598707486f5d8814ec9c01 ] When vfs_submount was added the test to limit automounts from filesystems that with s_user_ns !=3D &init_user_ns accidentially left in follow_automount. The test was never about any security concerns and was always about how do we implement this for filesystems whose s_user_ns !=3D &init_user_ns. At the moment this check makes no difference as there are no filesystems that both set FS_USERNS_MOUNT and implement d_automount. Remove this check now while I am thinking about it so there will not be odd booby traps for someone who does want to make this combination work. vfs_submount still needs improvements to allow this combination to work, and vfs_submount contains a check that presents a warning. The autofs4 filesystem could be modified to set FS_USERNS_MOUNT and it woul= d need not work on this code path, as userspace performs the mounts. Fixes: 93faccbbfa95 ("fs: Better permission checking for submounts") Fixes: aeaa4a79ff6a ("fs: Call d_automount with the filesystems creds") Acked-by: Ian Kent Signed-off-by: "Eric W. Biederman" Signed-off-by: Sasha Levin --- fs/namei.c | 3 --- 1 file changed, 3 deletions(-) diff --git a/fs/namei.c b/fs/namei.c index 6cfb45f262aa..917e7996b9c3 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -1121,9 +1121,6 @@ static int follow_automount(struct path *path, struct= nameidata *nd, path->dentry->d_inode) return -EISDIR; =20 - if (path->dentry->d_sb->s_user_ns !=3D &init_user_ns) - return -EACCES; - nd->total_link_count++; if (nd->total_link_count >=3D 40) return -ELOOP; --=20 2.14.1