// SPDX-License-Identifier: GPL-2.0-or-later

  /* getroot.c: get the root dentry for an NFS mount
   *
   * Copyright (C) 2006 Red Hat, Inc. All Rights Reserved.
   * Written by David Howells (dhowells@redhat.com)

   */

  #include <linux/module.h>
  #include <linux/init.h>
  
  #include <linux/time.h>
  #include <linux/kernel.h>
  #include <linux/mm.h>
  #include <linux/string.h>
  #include <linux/stat.h>
  #include <linux/errno.h>
  #include <linux/unistd.h>
  #include <linux/sunrpc/clnt.h>
  #include <linux/sunrpc/stats.h>
  #include <linux/nfs_fs.h>
  #include <linux/nfs_mount.h>

  #include <linux/lockd/bind.h>

  #include <linux/seq_file.h>
  #include <linux/mount.h>

  #include <linux/vfs.h>
  #include <linux/namei.h>

  #include <linux/security.h>

  #include <linux/uaccess.h>

  #include "internal.h"

  #define NFSDBG_FACILITY		NFSDBG_CLIENT

  
  /*

   * Set the superblock root dentry.
   * Note that this function frees the inode in case of error.
   */
  static int nfs_superblock_set_dummy_root(struct super_block *sb, struct inode *inode)
  {
  	/* The mntroot acts as the dummy root dentry for this superblock */
  	if (sb->s_root == NULL) {

  		sb->s_root = d_make_root(inode);
  		if (sb->s_root == NULL)

  			return -ENOMEM;

  		ihold(inode);

  		/*
  		 * Ensure that this dentry is invisible to d_find_alias().
  		 * Otherwise, it may be spliced into the tree by

  		 * d_splice_alias if a parent directory from the same

  		 * filesystem gets mounted at a later time.
  		 * This again causes shrink_dcache_for_umount_subtree() to
  		 * Oops, since the test for IS_ROOT() will fail.
  		 */

  		spin_lock(&d_inode(sb->s_root)->i_lock);

  		spin_lock(&sb->s_root->d_lock);

  		hlist_del_init(&sb->s_root->d_u.d_alias);

  		spin_unlock(&sb->s_root->d_lock);

  		spin_unlock(&d_inode(sb->s_root)->i_lock);

  	}
  	return 0;
  }
  
  /*

   * get an NFS2/NFS3 root dentry from the root filehandle
   */

  int nfs_get_root(struct super_block *s, struct fs_context *fc)

  {

  	struct nfs_fs_context *ctx = nfs_fc2context(fc);
  	struct nfs_server *server = NFS_SB(s);

  	struct nfs_fsinfo fsinfo;

  	struct dentry *root;

  	struct inode *inode;

  	char *name;
  	int error = -ENOMEM;

  	unsigned long kflags = 0, kflags_out = 0;

  	name = kstrdup(fc->source, GFP_KERNEL);

  	if (!name)

  		goto out;

  	/* get the actual root for this mount */

  	fsinfo.fattr = nfs_alloc_fattr();

  	if (fsinfo.fattr == NULL)
  		goto out_name;

  	fsinfo.fattr->label = nfs4_label_alloc(server, GFP_KERNEL);
  	if (IS_ERR(fsinfo.fattr->label))
  		goto out_fattr;

  	error = server->nfs_client->rpc_ops->getroot(server, ctx->mntfh, &fsinfo);

  	if (error < 0) {
  		dprintk("nfs_get_root: getattr error = %d
  ", -error);

  		nfs_errorf(fc, "NFS: Couldn't getattr on root");

  		goto out_label;

  	}

  	inode = nfs_fhget(s, ctx->mntfh, fsinfo.fattr, NULL);

  	if (IS_ERR(inode)) {
  		dprintk("nfs_get_root: get root inode failed
  ");

  		error = PTR_ERR(inode);

  		nfs_errorf(fc, "NFS: Couldn't get root inode");

  		goto out_label;

  	}

  	error = nfs_superblock_set_dummy_root(s, inode);
  	if (error != 0)

  		goto out_label;

  	/* root dentries normally start off anonymous and get spliced in later
  	 * if the dentry tree reaches them; however if the dentry already
  	 * exists, we'll pick it up at this point and use it as the root
  	 */

  	root = d_obtain_root(inode);
  	if (IS_ERR(root)) {

  		dprintk("nfs_get_root: get root dentry failed
  ");

  		error = PTR_ERR(root);

  		nfs_errorf(fc, "NFS: Couldn't get root dentry");

  		goto out_label;

  	}

  	security_d_instantiate(root, inode);
  	spin_lock(&root->d_lock);
  	if (IS_ROOT(root) && !root->d_fsdata &&
  	    !(root->d_flags & DCACHE_NFSFS_RENAMED)) {
  		root->d_fsdata = name;

  		name = NULL;
  	}

  	spin_unlock(&root->d_lock);
  	fc->root = root;

  	if (NFS_SB(s)->caps & NFS_CAP_SECURITY_LABEL)
  		kflags |= SECURITY_LSM_NATIVE_LABELS;
  	if (ctx->clone_data.sb) {
  		if (d_inode(fc->root)->i_fop != &nfs_dir_operations) {
  			error = -ESTALE;
  			goto error_splat_root;
  		}
  		/* clone lsm security options from the parent to the new sb */
  		error = security_sb_clone_mnt_opts(ctx->clone_data.sb,
  						   s, kflags, &kflags_out);
  	} else {
  		error = security_sb_set_mnt_opts(s, fc->security,
  							kflags, &kflags_out);
  	}
  	if (error)
  		goto error_splat_root;
  	if (NFS_SB(s)->caps & NFS_CAP_SECURITY_LABEL &&
  		!(kflags_out & SECURITY_LSM_NATIVE_LABELS))
  		NFS_SB(s)->caps &= ~NFS_CAP_SECURITY_LABEL;
  
  	nfs_setsecurity(inode, fsinfo.fattr, fsinfo.fattr->label);

  	error = 0;

  out_label:
  	nfs4_label_free(fsinfo.fattr->label);

  out_fattr:

  	nfs_free_fattr(fsinfo.fattr);

  out_name:
  	kfree(name);
  out:
  	return error;

  error_splat_root:
  	dput(fc->root);
  	fc->root = NULL;
  	goto out_label;

  }