summaryrefslogtreecommitdiff
path: root/fs/nfs/getroot.c
blob: 59355c106eceb5fb0d72d61834b385ffd3fe93d5 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
// 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), *clone_server;
	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\n", -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\n");
		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\n");
		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 (server->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);
		if (error)
			goto error_splat_root;
		clone_server = NFS_SB(ctx->clone_data.sb);
		server->has_sec_mnt_opts = clone_server->has_sec_mnt_opts;
	} else {
		error = security_sb_set_mnt_opts(s, fc->security,
							kflags, &kflags_out);
	}
	if (error)
		goto error_splat_root;
	if (server->caps & NFS_CAP_SECURITY_LABEL &&
		!(kflags_out & SECURITY_LSM_NATIVE_LABELS))
		server->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;
}