Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755182Ab2BUTx4 (ORCPT ); Tue, 21 Feb 2012 14:53:56 -0500 Received: from mx1.redhat.com ([209.132.183.28]:61599 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753922Ab2BUTxw (ORCPT ); Tue, 21 Feb 2012 14:53:52 -0500 Organization: Red Hat UK Ltd. Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903 From: David Howells Subject: [PATCH 37/73] union-mount: Prevent topmost file system from being mounted elsewhere [ver #2] To: linux-fsdevel@vger.kernel.org, viro@ZenIV.linux.org.uk, valerie.aurora@gmail.com Cc: linux-kernel@vger.kernel.org, David Howells Date: Tue, 21 Feb 2012 18:02:09 +0000 Message-ID: <20120221180209.25235.48782.stgit@warthog.procyon.org.uk> In-Reply-To: <20120221175721.25235.8901.stgit@warthog.procyon.org.uk> References: <20120221175721.25235.8901.stgit@warthog.procyon.org.uk> User-Agent: StGIT/0.14.3 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1301 Lines: 37 From: Valerie Aurora The device underlying the topmost read-write layer of a file system cannot be mounted anywhere else on the system. We keep a pointer to the union stack in the dentry of the topmost directory, so that dentry can't be part of a different mount, since dentries are shared between different mounts of the same device. Original-author: Valerie Aurora Signed-off-by: David Howells --- fs/namespace.c | 5 +++++ 1 files changed, 5 insertions(+), 0 deletions(-) diff --git a/fs/namespace.c b/fs/namespace.c index aa6b1ef..3c950fa 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -2091,6 +2091,11 @@ static int do_add_mount(struct mount *newmnt, struct path *path, int mnt_flags) if (S_ISLNK(newmnt->mnt.mnt_root->d_inode->i_mode)) goto unlock; + /* Top layers of union mounts can't be mounted elsewhere */ + err = -EBUSY; + if (newmnt->mnt.mnt_sb->s_union_lower_mnts) + goto unlock; + newmnt->mnt.mnt_flags = mnt_flags; err = graft_tree(newmnt, path); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/