Re: [PATCH] namespace.c: fix bind mount from foreign namespace

[Ram]

On Fri, 2005-05-13 at 03:44, Miklos Szeredi wrote:
> Bind mount from a foreign namespace results in an un-removable mount.

i wonder, should we even allow the ability to bind mount 
from a foreign namespace?  

The only time this is allowed is while creating a new namespace.

RP


> 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.
> 
> 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@xxxxxxxxxx>
> 
> 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 */
> -
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