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(&d_inode(sb->s_root)->i_lock); 56 spin_lock(&sb->s_root->d_lock); 57 hlist_del_init(&sb->s_root->d_u.d_alias); 58 spin_unlock(&sb->s_root->d_lock); 59 spin_unlock(&d_inode(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); 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(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(); 84 if (fsinfo.fattr == NULL) 85 goto out_name; 86 87 fsinfo.fattr->label = nfs4_label_alloc(server, GFP_KERNEL); 88 if (IS_ERR(fsinfo.fattr->label)) 89 goto out_fattr; 90 error = server->nfs_client->rpc_ops->getroot(server, ctx->mntfh, &fsinfo); 91 if (error < 0) { 92 dprintk("nfs_get_root: getattr error = %d\n", -error); 93 nfs_errorf(fc, "NFS: Couldn't getattr on root"); 94 goto out_label; 95 } 96 97 inode = nfs_fhget(s, ctx->mntfh, fsinfo.fattr, NULL); 98 if (IS_ERR(inode)) { 99 dprintk("nfs_get_root: get root inode failed\n"); 100 error = PTR_ERR(inode); 101 nfs_errorf(fc, "NFS: Couldn't get root inode"); 102 goto out_label; 103 } 104 105 error = nfs_superblock_set_dummy_root(s, inode); 106 if (error != 0) 107 goto out_label; 108 109 /* root dentries normally start off anonymous and get spliced in later 110 * if the dentry tree reaches them; however if the dentry already 111 * exists, we'll pick it up at this point and use it as the root 112 */ 113 root = d_obtain_root(inode); 114 if (IS_ERR(root)) { 115 dprintk("nfs_get_root: get root dentry failed\n"); 116 error = PTR_ERR(root); 117 nfs_errorf(fc, "NFS: Couldn't get root dentry"); 118 goto out_label; 119 } 120 121 security_d_instantiate(root, inode); 122 spin_lock(&root->d_lock); 123 if (IS_ROOT(root) && !root->d_fsdata && 124 !(root->d_flags & DCACHE_NFSFS_RENAMED)) { 125 root->d_fsdata = name; 126 name = NULL; 127 } 128 spin_unlock(&root->d_lock); 129 fc->root = root; 130 if (NFS_SB(s)->caps & NFS_CAP_SECURITY_LABEL) 131 kflags |= SECURITY_LSM_NATIVE_LABELS; 132 if (ctx->clone_data.sb) { 133 if (d_inode(fc->root)->i_fop != &nfs_dir_operations) { 134 error = -ESTALE; 135 goto error_splat_root; 136 } 137 /* clone lsm security options from the parent to the new sb */ 138 error = security_sb_clone_mnt_opts(ctx->clone_data.sb, 139 s, kflags, &kflags_out); 140 } else { 141 error = security_sb_set_mnt_opts(s, fc->security, 142 kflags, &kflags_out); 143 } 144 if (error) 145 goto error_splat_root; 146 if (NFS_SB(s)->caps & NFS_CAP_SECURITY_LABEL && 147 !(kflags_out & SECURITY_LSM_NATIVE_LABELS)) 148 NFS_SB(s)->caps &= ~NFS_CAP_SECURITY_LABEL; 149 150 nfs_setsecurity(inode, fsinfo.fattr, fsinfo.fattr->label); 151 error = 0; 152 153 out_label: 154 nfs4_label_free(fsinfo.fattr->label); 155 out_fattr: 156 nfs_free_fattr(fsinfo.fattr); 157 out_name: 158 kfree(name); 159 out: 160 return error; 161 error_splat_root: 162 dput(fc->root); 163 fc->root = NULL; 164 goto out_label; 165 } 166