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

[Miklos Szeredi]

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.

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 */
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/