Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755472Ab2BUTx7 (ORCPT ); Tue, 21 Feb 2012 14:53:59 -0500 Received: from mx1.redhat.com ([209.132.183.28]:2177 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753981Ab2BUTxw (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 36/73] union-mount: Prevent improper union-related remounts [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 18:02:01 +0000 Message-ID: <20120221180201.25235.32109.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: 1513 Lines: 47 From: Valerie Aurora A remount request must not (a) convert a union to a non-union (or vice versa), or (b) make the topmost layer of a union read-only. Note that we only have to worry about attempts to remount the vfsmount of the topmost read-write of the union (the one with MNT_UNION set). The vfsmounts of the read-only layers are hidden in a cloned tree hanging of the superblock of the topmost layer and aren't visible to userspace. Original-author: Valerie Aurora Signed-off-by: David Howells --- fs/namespace.c | 12 ++++++++++++ 1 files changed, 12 insertions(+), 0 deletions(-) diff --git a/fs/namespace.c b/fs/namespace.c index 261944d..aa6b1ef 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -1907,6 +1907,18 @@ static int do_remount(struct path *path, int flags, int mnt_flags, if (!check_mnt(mnt)) return -EINVAL; + if ((path->mnt->mnt_flags & MNT_UNION) && + !(mnt_flags & MNT_UNION)) + return -EINVAL; + + if ((mnt_flags & MNT_UNION) && + !(path->mnt->mnt_flags & MNT_UNION)) + return -EINVAL; + + if ((path->mnt->mnt_flags & MNT_UNION) && + (mnt_flags & MNT_READONLY)) + return -EINVAL; + if (path->dentry != path->mnt->mnt_root) return -EINVAL; -- 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/