NFS: Secure the roots of the NFS subtrees in a shared superblock

Invoke security_d_instantiate() on root dentries after allocating them with
dentry_alloc_anon().  Normally dentry_alloc_root() would do that, but we don't
call that as we don't want to assign a name to the root dentry at this point
(we may discover the real name later).
Signed-Off-By: David Howells <dhowells@redhat.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

fs/nfs/getroot.c

@@ -33,6 +33,7 @@
 #include <linux/vfs.h>
 #include <linux/namei.h>
 #include <linux/namespace.h>
+#include <linux/security.h>
 
 #include <asm/system.h>
 #include <asm/uaccess.h>
@@ -109,6 +110,8 @@ struct dentry *nfs_get_root(struct super_block *sb, struct nfs_fh *mntfh)
 		return ERR_PTR(-ENOMEM);
 	}
 
+	security_d_instantiate(mntroot, inode);
+
 	if (!mntroot->d_op)
 		mntroot->d_op = server->nfs_client->rpc_ops->dentry_ops;
 
@@ -296,6 +299,8 @@ struct dentry *nfs4_get_root(struct super_block *sb, struct nfs_fh *mntfh)
 		return ERR_PTR(-ENOMEM);
 	}
 
+	security_d_instantiate(mntroot, inode);
+
 	if (!mntroot->d_op)
 		mntroot->d_op = server->nfs_client->rpc_ops->dentry_ops;