12874c5fdSThomas Gleixner // SPDX-License-Identifier: GPL-2.0-or-later
254ceac45SDavid Howells /* getroot.c: get the root dentry for an NFS mount
354ceac45SDavid Howells *
454ceac45SDavid Howells * Copyright (C) 2006 Red Hat, Inc. All Rights Reserved.
554ceac45SDavid Howells * Written by David Howells (dhowells@redhat.com)
654ceac45SDavid Howells */
754ceac45SDavid Howells
854ceac45SDavid Howells #include <linux/module.h>
954ceac45SDavid Howells #include <linux/init.h>
1054ceac45SDavid Howells
1154ceac45SDavid Howells #include <linux/time.h>
1254ceac45SDavid Howells #include <linux/kernel.h>
1354ceac45SDavid Howells #include <linux/mm.h>
1454ceac45SDavid Howells #include <linux/string.h>
1554ceac45SDavid Howells #include <linux/stat.h>
1654ceac45SDavid Howells #include <linux/errno.h>
1754ceac45SDavid Howells #include <linux/unistd.h>
1854ceac45SDavid Howells #include <linux/sunrpc/clnt.h>
1954ceac45SDavid Howells #include <linux/sunrpc/stats.h>
2054ceac45SDavid Howells #include <linux/nfs_fs.h>
2154ceac45SDavid Howells #include <linux/nfs_mount.h>
2254ceac45SDavid Howells #include <linux/lockd/bind.h>
2354ceac45SDavid Howells #include <linux/seq_file.h>
2454ceac45SDavid Howells #include <linux/mount.h>
2554ceac45SDavid Howells #include <linux/vfs.h>
2654ceac45SDavid Howells #include <linux/namei.h>
27738a3519SDavid Howells #include <linux/security.h>
2854ceac45SDavid Howells
297c0f6ba6SLinus Torvalds #include <linux/uaccess.h>
3054ceac45SDavid Howells
314e437e95SStanislav Kinsbursky #include "internal.h"
324e437e95SStanislav Kinsbursky
3354ceac45SDavid Howells #define NFSDBG_FACILITY NFSDBG_CLIENT
3454ceac45SDavid Howells
3554ceac45SDavid Howells /*
36b09b9417STrond Myklebust * Set the superblock root dentry.
37b09b9417STrond Myklebust * Note that this function frees the inode in case of error.
38b09b9417STrond Myklebust */
nfs_superblock_set_dummy_root(struct super_block * sb,struct inode * inode)39b09b9417STrond Myklebust static int nfs_superblock_set_dummy_root(struct super_block *sb, struct inode *inode)
40b09b9417STrond Myklebust {
41b09b9417STrond Myklebust /* The mntroot acts as the dummy root dentry for this superblock */
42b09b9417STrond Myklebust if (sb->s_root == NULL) {
4348fde701SAl Viro sb->s_root = d_make_root(inode);
4448fde701SAl Viro if (sb->s_root == NULL)
45b09b9417STrond Myklebust return -ENOMEM;
467de9c6eeSAl Viro ihold(inode);
47a10db50aSTrond Myklebust /*
48a10db50aSTrond Myklebust * Ensure that this dentry is invisible to d_find_alias().
49a10db50aSTrond Myklebust * Otherwise, it may be spliced into the tree by
5041d28bcaSAl Viro * d_splice_alias if a parent directory from the same
51a10db50aSTrond Myklebust * filesystem gets mounted at a later time.
52a10db50aSTrond Myklebust * This again causes shrink_dcache_for_umount_subtree() to
53a10db50aSTrond Myklebust * Oops, since the test for IS_ROOT() will fail.
54a10db50aSTrond Myklebust */
552b0143b5SDavid Howells spin_lock(&d_inode(sb->s_root)->i_lock);
56b23fb0a6SNick Piggin spin_lock(&sb->s_root->d_lock);
57946e51f2SAl Viro hlist_del_init(&sb->s_root->d_u.d_alias);
58b23fb0a6SNick Piggin spin_unlock(&sb->s_root->d_lock);
592b0143b5SDavid Howells spin_unlock(&d_inode(sb->s_root)->i_lock);
60b09b9417STrond Myklebust }
61b09b9417STrond Myklebust return 0;
62b09b9417STrond Myklebust }
63b09b9417STrond Myklebust
64b09b9417STrond Myklebust /*
6554ceac45SDavid Howells * get an NFS2/NFS3 root dentry from the root filehandle
6654ceac45SDavid Howells */
nfs_get_root(struct super_block * s,struct fs_context * fc)6762a55d08SScott Mayhew int nfs_get_root(struct super_block *s, struct fs_context *fc)
6854ceac45SDavid Howells {
6962a55d08SScott Mayhew struct nfs_fs_context *ctx = nfs_fc2context(fc);
70eae00c5dSScott Mayhew struct nfs_server *server = NFS_SB(s), *clone_server;
7154ceac45SDavid Howells struct nfs_fsinfo fsinfo;
7262a55d08SScott Mayhew struct dentry *root;
7354ceac45SDavid Howells struct inode *inode;
7462a55d08SScott Mayhew char *name;
7562a55d08SScott Mayhew int error = -ENOMEM;
76779df6a5SScott Mayhew unsigned long kflags = 0, kflags_out = 0;
7754ceac45SDavid Howells
7862a55d08SScott Mayhew name = kstrdup(fc->source, GFP_KERNEL);
79b1942c5fSAl Viro if (!name)
8062a55d08SScott Mayhew goto out;
81b1942c5fSAl Viro
8254ceac45SDavid Howells /* get the actual root for this mount */
83d755ad8dSAnna Schumaker fsinfo.fattr = nfs_alloc_fattr_with_label(server);
8462a55d08SScott Mayhew if (fsinfo.fattr == NULL)
8562a55d08SScott Mayhew goto out_name;
8654ceac45SDavid Howells
8762a55d08SScott Mayhew error = server->nfs_client->rpc_ops->getroot(server, ctx->mntfh, &fsinfo);
8854ceac45SDavid Howells if (error < 0) {
8954ceac45SDavid Howells dprintk("nfs_get_root: getattr error = %d\n", -error);
90ce8866f0SScott Mayhew nfs_errorf(fc, "NFS: Couldn't getattr on root");
91d755ad8dSAnna Schumaker goto out_fattr;
9254ceac45SDavid Howells }
9354ceac45SDavid Howells
94cf7ab00aSAnna Schumaker inode = nfs_fhget(s, ctx->mntfh, fsinfo.fattr);
9554ceac45SDavid Howells if (IS_ERR(inode)) {
9654ceac45SDavid Howells dprintk("nfs_get_root: get root inode failed\n");
9762a55d08SScott Mayhew error = PTR_ERR(inode);
98ce8866f0SScott Mayhew nfs_errorf(fc, "NFS: Couldn't get root inode");
99d755ad8dSAnna Schumaker goto out_fattr;
10054ceac45SDavid Howells }
10154ceac45SDavid Howells
10262a55d08SScott Mayhew error = nfs_superblock_set_dummy_root(s, inode);
10362a55d08SScott Mayhew if (error != 0)
104d755ad8dSAnna Schumaker goto out_fattr;
105b09b9417STrond Myklebust
10654ceac45SDavid Howells /* root dentries normally start off anonymous and get spliced in later
10754ceac45SDavid Howells * if the dentry tree reaches them; however if the dentry already
10854ceac45SDavid Howells * exists, we'll pick it up at this point and use it as the root
10954ceac45SDavid Howells */
11062a55d08SScott Mayhew root = d_obtain_root(inode);
11162a55d08SScott Mayhew if (IS_ERR(root)) {
11254ceac45SDavid Howells dprintk("nfs_get_root: get root dentry failed\n");
11362a55d08SScott Mayhew error = PTR_ERR(root);
114ce8866f0SScott Mayhew nfs_errorf(fc, "NFS: Couldn't get root dentry");
115d755ad8dSAnna Schumaker goto out_fattr;
11654ceac45SDavid Howells }
11754ceac45SDavid Howells
11862a55d08SScott Mayhew security_d_instantiate(root, inode);
11962a55d08SScott Mayhew spin_lock(&root->d_lock);
12062a55d08SScott Mayhew if (IS_ROOT(root) && !root->d_fsdata &&
12162a55d08SScott Mayhew !(root->d_flags & DCACHE_NFSFS_RENAMED)) {
12262a55d08SScott Mayhew root->d_fsdata = name;
123b1942c5fSAl Viro name = NULL;
124b1942c5fSAl Viro }
12562a55d08SScott Mayhew spin_unlock(&root->d_lock);
12662a55d08SScott Mayhew fc->root = root;
127eae00c5dSScott Mayhew if (server->caps & NFS_CAP_SECURITY_LABEL)
128779df6a5SScott Mayhew kflags |= SECURITY_LSM_NATIVE_LABELS;
129779df6a5SScott Mayhew if (ctx->clone_data.sb) {
130779df6a5SScott Mayhew if (d_inode(fc->root)->i_fop != &nfs_dir_operations) {
131779df6a5SScott Mayhew error = -ESTALE;
132779df6a5SScott Mayhew goto error_splat_root;
133779df6a5SScott Mayhew }
134779df6a5SScott Mayhew /* clone lsm security options from the parent to the new sb */
135779df6a5SScott Mayhew error = security_sb_clone_mnt_opts(ctx->clone_data.sb,
136779df6a5SScott Mayhew s, kflags, &kflags_out);
137eae00c5dSScott Mayhew if (error)
138eae00c5dSScott Mayhew goto error_splat_root;
139eae00c5dSScott Mayhew clone_server = NFS_SB(ctx->clone_data.sb);
140eae00c5dSScott Mayhew server->has_sec_mnt_opts = clone_server->has_sec_mnt_opts;
141779df6a5SScott Mayhew } else {
142779df6a5SScott Mayhew error = security_sb_set_mnt_opts(s, fc->security,
143779df6a5SScott Mayhew kflags, &kflags_out);
144779df6a5SScott Mayhew }
145779df6a5SScott Mayhew if (error)
146779df6a5SScott Mayhew goto error_splat_root;
147eae00c5dSScott Mayhew if (server->caps & NFS_CAP_SECURITY_LABEL &&
148779df6a5SScott Mayhew !(kflags_out & SECURITY_LSM_NATIVE_LABELS))
149eae00c5dSScott Mayhew server->caps &= ~NFS_CAP_SECURITY_LABEL;
150779df6a5SScott Mayhew
151*dd225cb3SAnna Schumaker nfs_setsecurity(inode, fsinfo.fattr);
15262a55d08SScott Mayhew error = 0;
15362a55d08SScott Mayhew
15462a55d08SScott Mayhew out_fattr:
1558bac9db9STrond Myklebust nfs_free_fattr(fsinfo.fattr);
15662a55d08SScott Mayhew out_name:
15762a55d08SScott Mayhew kfree(name);
15862a55d08SScott Mayhew out:
15962a55d08SScott Mayhew return error;
160779df6a5SScott Mayhew error_splat_root:
161779df6a5SScott Mayhew dput(fc->root);
162779df6a5SScott Mayhew fc->root = NULL;
163d755ad8dSAnna Schumaker goto out_fattr;
16454ceac45SDavid Howells }
165