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 * get a root dentry from the root filehandle 37 */ 38 int nfs_get_root(struct super_block *s, struct fs_context *fc) 39 { 40 struct nfs_fs_context *ctx = nfs_fc2context(fc); 41 struct nfs_server *server = NFS_SB(s), *clone_server; 42 struct nfs_fsinfo fsinfo; 43 struct dentry *root; 44 struct inode *inode; 45 char *name; 46 int error = -ENOMEM; 47 unsigned long kflags = 0, kflags_out = 0; 48 49 name = kstrdup(fc->source, GFP_KERNEL); 50 if (!name) 51 goto out; 52 53 /* get the actual root for this mount */ 54 fsinfo.fattr = nfs_alloc_fattr_with_label(server); 55 if (fsinfo.fattr == NULL) 56 goto out_name; 57 58 error = server->nfs_client->rpc_ops->getroot(server, ctx->mntfh, &fsinfo); 59 if (error < 0) { 60 dprintk("nfs_get_root: getattr error = %d\n", -error); 61 nfs_errorf(fc, "NFS: Couldn't getattr on root"); 62 goto out_fattr; 63 } 64 65 inode = nfs_fhget(s, ctx->mntfh, fsinfo.fattr); 66 if (IS_ERR(inode)) { 67 dprintk("nfs_get_root: get root inode failed\n"); 68 error = PTR_ERR(inode); 69 nfs_errorf(fc, "NFS: Couldn't get root inode"); 70 goto out_fattr; 71 } 72 73 /* root dentries normally start off anonymous and get spliced in later 74 * if the dentry tree reaches them; however if the dentry already 75 * exists, we'll pick it up at this point and use it as the root 76 */ 77 root = d_obtain_root(inode); 78 if (IS_ERR(root)) { 79 dprintk("nfs_get_root: get root dentry failed\n"); 80 error = PTR_ERR(root); 81 nfs_errorf(fc, "NFS: Couldn't get root dentry"); 82 goto out_fattr; 83 } 84 85 security_d_instantiate(root, inode); 86 spin_lock(&root->d_lock); 87 if (IS_ROOT(root) && !root->d_fsdata && 88 !(root->d_flags & DCACHE_NFSFS_RENAMED)) { 89 root->d_fsdata = name; 90 name = NULL; 91 } 92 spin_unlock(&root->d_lock); 93 if (!s->s_root) 94 s->s_root = dget(root); 95 fc->root = root; 96 if (server->caps & NFS_CAP_SECURITY_LABEL) 97 kflags |= SECURITY_LSM_NATIVE_LABELS; 98 if (ctx->clone_data.sb) { 99 if (d_inode(fc->root)->i_fop != &nfs_dir_operations) { 100 error = -ESTALE; 101 goto error_splat_root; 102 } 103 /* clone lsm security options from the parent to the new sb */ 104 error = security_sb_clone_mnt_opts(ctx->clone_data.sb, 105 s, kflags, &kflags_out); 106 if (error) 107 goto error_splat_root; 108 clone_server = NFS_SB(ctx->clone_data.sb); 109 server->has_sec_mnt_opts = clone_server->has_sec_mnt_opts; 110 } else { 111 error = security_sb_set_mnt_opts(s, fc->security, 112 kflags, &kflags_out); 113 } 114 if (error) 115 goto error_splat_root; 116 if (server->caps & NFS_CAP_SECURITY_LABEL && 117 !(kflags_out & SECURITY_LSM_NATIVE_LABELS)) 118 server->caps &= ~NFS_CAP_SECURITY_LABEL; 119 120 nfs_setsecurity(inode, fsinfo.fattr); 121 error = 0; 122 123 out_fattr: 124 nfs_free_fattr(fsinfo.fattr); 125 out_name: 126 kfree(name); 127 out: 128 return error; 129 error_splat_root: 130 dput(fc->root); 131 fc->root = NULL; 132 goto out_fattr; 133 } 134