Date: Mon, 08 Nov 2004 11:20:27 -0500
From: Mike Waychison <Michael.Waychison@Sun.COM>
Subject: Re: [PATCH] Mounting on floating mounts is possible
In-reply-to: <20041106060455.0100e3ec@doener>
To: =?ISO-8859-1?Q?Bj=F6rn_Steinbrink?= <B.Steinbrink@gmx.de>
Cc: viro@parcelfarce.linux.theplanet.co.uk, linux-kernel@vger.kernel.org
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Bj?rn Steinbrink wrote:
> Hi,
> 
> this[1] patch changed check_mnt() so that mounting on a floating mount
> (i.e. one that was unmounted using MNT_DETACH and was still in use) is
> possible, since we no longer check if the mountpoint is actually
> reachable. The problem is that we may lose any reference to the floating
> mount, but the mount on it will keep it alive, thus it will never go
> away. The following patch removes the reference from the mount to its
> namespace when it is unmounted lazily, so that check_mnt protects from
> such mounts.
> 
> Please CC me as I'm not subscribed to the list.
> 
> Bjoern
> 
> [1] http://lwn.net/Articles/91946/
> 
> diff -uNr --minimal a/fs/namespace.c b/fs/namespace.c
> --- a/fs/namespace.c    2004-10-31 00:41:02.000000000 +0200
> +++ b/fs/namespace.c    2004-11-06 04:38:37.299013810 +0100
> @@ -358,6 +358,7 @@
>                 } else {
>                         struct nameidata old_nd;
>                         detach_mnt(mnt, &old_nd);
> +                       mnt->mnt_namespace = NULL;
>                         spin_unlock(&vfsmount_lock);
>                         path_release(&old_nd);
>                 }
> -

I don't think this patch clears mnt_namespace for the root of the
umounted tree.  How about this?


- --
Mike Waychison
Sun Microsystems, Inc.
1 (650) 352-5299 voice
1 (416) 202-8336 voice

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---

 namespace.c |    1 +
 1 files changed, 1 insertion(+)

Index: linux-2.6.9-quilt/fs/namespace.c
===================================================================
--- linux-2.6.9-quilt.orig/fs/namespace.c	2004-11-08 11:18:39.980358880 -0500
+++ linux-2.6.9-quilt/fs/namespace.c	2004-11-08 11:19:24.702560072 -0500
@@ -352,6 +352,7 @@ void umount_tree(struct vfsmount *mnt)
 		mnt = list_entry(kill.next, struct vfsmount, mnt_list);
 		list_del_init(&mnt->mnt_list);
 		list_del_init(&mnt->mnt_fslink);
+		mnt->mnt_namespace = NULL;
 		if (mnt->mnt_parent == mnt) {
 			spin_unlock(&vfsmount_lock);
 		} else {

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