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 <[email protected]>
Index: linux/fs/namespace.c
===================================================================
--- linux.orig/fs/namespace.c 2005-05-13 12:22:52.000000000 +0200
+++ linux/fs/namespace.c 2005-05-13 12:32:36.000000000 +0200
@@ -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 */
Miklos Szeredi wrote:
> 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 <[email protected]>
This patch is correct. The old code was buggy for more fundamental
and serious reason: it broke the invariant that a tree of vfsmnts all
have the same value of mnt_namespace (and the same for the mnt_list
list).
Signed-off-by: Jamie Lokier <[email protected]>
> Index: linux/fs/namespace.c
> ===================================================================
> --- linux.orig/fs/namespace.c 2005-05-13 12:22:52.000000000 +0200
> +++ linux/fs/namespace.c 2005-05-13 12:32:36.000000000 +0200
> @@ -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 */