1 | // SPDX-License-Identifier: GPL-2.0-or-later |
2 | /* getroot.c: get the root dentry for an NFS mount |
3 | * |
4 | * Copyright (C) 2006 Red Hat, Inc. All Rights Reserved. |
5 | * Written by David Howells (dhowells@redhat.com) |
6 | */ |
7 | |
8 | #include <linux/module.h> |
9 | #include <linux/init.h> |
10 | |
11 | #include <linux/time.h> |
12 | #include <linux/kernel.h> |
13 | #include <linux/mm.h> |
14 | #include <linux/string.h> |
15 | #include <linux/stat.h> |
16 | #include <linux/errno.h> |
17 | #include <linux/unistd.h> |
18 | #include <linux/sunrpc/clnt.h> |
19 | #include <linux/sunrpc/stats.h> |
20 | #include <linux/nfs_fs.h> |
21 | #include <linux/nfs_mount.h> |
22 | #include <linux/lockd/bind.h> |
23 | #include <linux/seq_file.h> |
24 | #include <linux/mount.h> |
25 | #include <linux/vfs.h> |
26 | #include <linux/namei.h> |
27 | #include <linux/security.h> |
28 | |
29 | #include <linux/uaccess.h> |
30 | |
31 | #include "internal.h" |
32 | |
33 | #define NFSDBG_FACILITY NFSDBG_CLIENT |
34 | |
35 | /* |
36 | * Set the superblock root dentry. |
37 | * Note that this function frees the inode in case of error. |
38 | */ |
39 | static int nfs_superblock_set_dummy_root(struct super_block *sb, struct inode *inode) |
40 | { |
41 | /* The mntroot acts as the dummy root dentry for this superblock */ |
42 | if (sb->s_root == NULL) { |
43 | sb->s_root = d_make_root(inode); |
44 | if (sb->s_root == NULL) |
45 | return -ENOMEM; |
46 | ihold(inode); |
47 | /* |
48 | * Ensure that this dentry is invisible to d_find_alias(). |
49 | * Otherwise, it may be spliced into the tree by |
50 | * d_splice_alias if a parent directory from the same |
51 | * filesystem gets mounted at a later time. |
52 | * This again causes shrink_dcache_for_umount_subtree() to |
53 | * Oops, since the test for IS_ROOT() will fail. |
54 | */ |
55 | spin_lock(lock: &d_inode(dentry: sb->s_root)->i_lock); |
56 | spin_lock(lock: &sb->s_root->d_lock); |
57 | hlist_del_init(n: &sb->s_root->d_u.d_alias); |
58 | spin_unlock(lock: &sb->s_root->d_lock); |
59 | spin_unlock(lock: &d_inode(dentry: sb->s_root)->i_lock); |
60 | } |
61 | return 0; |
62 | } |
63 | |
64 | /* |
65 | * get an NFS2/NFS3 root dentry from the root filehandle |
66 | */ |
67 | int nfs_get_root(struct super_block *s, struct fs_context *fc) |
68 | { |
69 | struct nfs_fs_context *ctx = nfs_fc2context(fc); |
70 | struct nfs_server *server = NFS_SB(s), *clone_server; |
71 | struct nfs_fsinfo fsinfo; |
72 | struct dentry *root; |
73 | struct inode *inode; |
74 | char *name; |
75 | int error = -ENOMEM; |
76 | unsigned long kflags = 0, kflags_out = 0; |
77 | |
78 | name = kstrdup(s: fc->source, GFP_KERNEL); |
79 | if (!name) |
80 | goto out; |
81 | |
82 | /* get the actual root for this mount */ |
83 | fsinfo.fattr = nfs_alloc_fattr_with_label(server); |
84 | if (fsinfo.fattr == NULL) |
85 | goto out_name; |
86 | |
87 | error = server->nfs_client->rpc_ops->getroot(server, ctx->mntfh, &fsinfo); |
88 | if (error < 0) { |
89 | dprintk("nfs_get_root: getattr error = %d\n" , -error); |
90 | nfs_errorf(fc, "NFS: Couldn't getattr on root" ); |
91 | goto out_fattr; |
92 | } |
93 | |
94 | inode = nfs_fhget(s, ctx->mntfh, fsinfo.fattr); |
95 | if (IS_ERR(ptr: inode)) { |
96 | dprintk("nfs_get_root: get root inode failed\n" ); |
97 | error = PTR_ERR(ptr: inode); |
98 | nfs_errorf(fc, "NFS: Couldn't get root inode" ); |
99 | goto out_fattr; |
100 | } |
101 | |
102 | error = nfs_superblock_set_dummy_root(sb: s, inode); |
103 | if (error != 0) |
104 | goto out_fattr; |
105 | |
106 | /* root dentries normally start off anonymous and get spliced in later |
107 | * if the dentry tree reaches them; however if the dentry already |
108 | * exists, we'll pick it up at this point and use it as the root |
109 | */ |
110 | root = d_obtain_root(inode); |
111 | if (IS_ERR(ptr: root)) { |
112 | dprintk("nfs_get_root: get root dentry failed\n" ); |
113 | error = PTR_ERR(ptr: root); |
114 | nfs_errorf(fc, "NFS: Couldn't get root dentry" ); |
115 | goto out_fattr; |
116 | } |
117 | |
118 | security_d_instantiate(dentry: root, inode); |
119 | spin_lock(lock: &root->d_lock); |
120 | if (IS_ROOT(root) && !root->d_fsdata && |
121 | !(root->d_flags & DCACHE_NFSFS_RENAMED)) { |
122 | root->d_fsdata = name; |
123 | name = NULL; |
124 | } |
125 | spin_unlock(lock: &root->d_lock); |
126 | fc->root = root; |
127 | if (server->caps & NFS_CAP_SECURITY_LABEL) |
128 | kflags |= SECURITY_LSM_NATIVE_LABELS; |
129 | if (ctx->clone_data.sb) { |
130 | if (d_inode(dentry: fc->root)->i_fop != &nfs_dir_operations) { |
131 | error = -ESTALE; |
132 | goto error_splat_root; |
133 | } |
134 | /* clone lsm security options from the parent to the new sb */ |
135 | error = security_sb_clone_mnt_opts(oldsb: ctx->clone_data.sb, |
136 | newsb: s, kern_flags: kflags, set_kern_flags: &kflags_out); |
137 | if (error) |
138 | goto error_splat_root; |
139 | clone_server = NFS_SB(s: ctx->clone_data.sb); |
140 | server->has_sec_mnt_opts = clone_server->has_sec_mnt_opts; |
141 | } else { |
142 | error = security_sb_set_mnt_opts(sb: s, mnt_opts: fc->security, |
143 | kern_flags: kflags, set_kern_flags: &kflags_out); |
144 | } |
145 | if (error) |
146 | goto error_splat_root; |
147 | if (server->caps & NFS_CAP_SECURITY_LABEL && |
148 | !(kflags_out & SECURITY_LSM_NATIVE_LABELS)) |
149 | server->caps &= ~NFS_CAP_SECURITY_LABEL; |
150 | |
151 | nfs_setsecurity(inode, fattr: fsinfo.fattr); |
152 | error = 0; |
153 | |
154 | out_fattr: |
155 | nfs_free_fattr(fattr: fsinfo.fattr); |
156 | out_name: |
157 | kfree(objp: name); |
158 | out: |
159 | return error; |
160 | error_splat_root: |
161 | dput(fc->root); |
162 | fc->root = NULL; |
163 | goto out_fattr; |
164 | } |
165 | |