From: Miklos Szeredi <miklos@szeredi.hu>

I'm resending this patch, because I still believe it's the correct fix.

Tested before/after applying the patch with a test application
available from:

  http://www.inf.bme.hu/~mszeredi/nstest.c

Bind mount from a foreign namespace results in an un-removable mount.
The reason is that mnt->mnt_namespace is copied from the old mount in
clone_mnt().  Because of this check_mnt() in sys_umount() will fail.

The solution is to set mnt->mnt_namespace to current->namespace in
clone_mnt().  clone_mnt() is either called from do_loopback() or
copy_tree().  copy_tree() is called from do_loopback() or
copy_namespace().

When called (directly or indirectly) from do_loopback(), always
current->namspace is being modified: check_mnt(nd->mnt).  So setting
mnt->mnt_namespace to current->namspace is the right thing to do.

When called from copy_namespace(), the setting of mnt_namespace is
irrelevant, since mnt_namespace is reset later in that function for
all copied mounts.

Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---

 fs/namespace.c |    2 +-
 1 files changed, 1 insertion(+), 1 deletion(-)

diff -puN fs/namespace.c~namespacec-fix-bind-mount-from-foreign-namespace fs/namespace.c
--- 25/fs/namespace.c~namespacec-fix-bind-mount-from-foreign-namespace	Mon May 16 14:56:25 2005
+++ 25-akpm/fs/namespace.c	Mon May 16 14:56:25 2005
@@ -160,7 +160,7 @@ clone_mnt(struct vfsmount *old, struct d
 		mnt->mnt_root = dget(root);
 		mnt->mnt_mountpoint = mnt->mnt_root;
 		mnt->mnt_parent = mnt;
-		mnt->mnt_namespace = old->mnt_namespace;
+		mnt->mnt_namespace = current->namespace;
 
 		/* stick the duplicate mount on the same expiry list
 		 * as the original if that was on one */
_