1 /* getroot.c: get the root dentry for an NFS mount 2 * 3 * Copyright (C) 2006 Red Hat, Inc. All Rights Reserved. 4 * Written by David Howells (dhowells@redhat.com) 5 * 6 * This program is free software; you can redistribute it and/or 7 * modify it under the terms of the GNU General Public License 8 * as published by the Free Software Foundation; either version 9 * 2 of the License, or (at your option) any later version. 10 */ 11 12 #include <linux/module.h> 13 #include <linux/init.h> 14 15 #include <linux/time.h> 16 #include <linux/kernel.h> 17 #include <linux/mm.h> 18 #include <linux/string.h> 19 #include <linux/stat.h> 20 #include <linux/errno.h> 21 #include <linux/unistd.h> 22 #include <linux/sunrpc/clnt.h> 23 #include <linux/sunrpc/stats.h> 24 #include <linux/nfs_fs.h> 25 #include <linux/nfs_mount.h> 26 #include <linux/nfs4_mount.h> 27 #include <linux/lockd/bind.h> 28 #include <linux/seq_file.h> 29 #include <linux/mount.h> 30 #include <linux/nfs_idmap.h> 31 #include <linux/vfs.h> 32 #include <linux/namei.h> 33 #include <linux/mnt_namespace.h> 34 #include <linux/security.h> 35 36 #include <asm/system.h> 37 #include <asm/uaccess.h> 38 39 #include "nfs4_fs.h" 40 #include "delegation.h" 41 #include "internal.h" 42 43 #define NFSDBG_FACILITY NFSDBG_CLIENT 44 45 /* 46 * Set the superblock root dentry. 47 * Note that this function frees the inode in case of error. 48 */ 49 static int nfs_superblock_set_dummy_root(struct super_block *sb, struct inode *inode) 50 { 51 /* The mntroot acts as the dummy root dentry for this superblock */ 52 if (sb->s_root == NULL) { 53 sb->s_root = d_alloc_root(inode); 54 if (sb->s_root == NULL) { 55 iput(inode); 56 return -ENOMEM; 57 } 58 /* Circumvent igrab(): we know the inode is not being freed */ 59 atomic_inc(&inode->i_count); 60 /* 61 * Ensure that this dentry is invisible to d_find_alias(). 62 * Otherwise, it may be spliced into the tree by 63 * d_materialise_unique if a parent directory from the same 64 * filesystem gets mounted at a later time. 65 * This again causes shrink_dcache_for_umount_subtree() to 66 * Oops, since the test for IS_ROOT() will fail. 67 */ 68 spin_lock(&dcache_lock); 69 list_del_init(&sb->s_root->d_alias); 70 spin_unlock(&dcache_lock); 71 } 72 return 0; 73 } 74 75 /* 76 * get an NFS2/NFS3 root dentry from the root filehandle 77 */ 78 struct dentry *nfs_get_root(struct super_block *sb, struct nfs_fh *mntfh) 79 { 80 struct nfs_server *server = NFS_SB(sb); 81 struct nfs_fsinfo fsinfo; 82 struct nfs_fattr fattr; 83 struct dentry *mntroot; 84 struct inode *inode; 85 int error; 86 87 /* get the actual root for this mount */ 88 fsinfo.fattr = &fattr; 89 90 error = server->nfs_client->rpc_ops->getroot(server, mntfh, &fsinfo); 91 if (error < 0) { 92 dprintk("nfs_get_root: getattr error = %d\n", -error); 93 return ERR_PTR(error); 94 } 95 96 inode = nfs_fhget(sb, mntfh, fsinfo.fattr); 97 if (IS_ERR(inode)) { 98 dprintk("nfs_get_root: get root inode failed\n"); 99 return ERR_CAST(inode); 100 } 101 102 error = nfs_superblock_set_dummy_root(sb, inode); 103 if (error != 0) 104 return ERR_PTR(error); 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 mntroot = d_alloc_anon(inode); 111 if (!mntroot) { 112 iput(inode); 113 dprintk("nfs_get_root: get root dentry failed\n"); 114 return ERR_PTR(-ENOMEM); 115 } 116 117 security_d_instantiate(mntroot, inode); 118 119 if (!mntroot->d_op) 120 mntroot->d_op = server->nfs_client->rpc_ops->dentry_ops; 121 122 return mntroot; 123 } 124 125 #ifdef CONFIG_NFS_V4 126 127 /* 128 * Do a simple pathwalk from the root FH of the server to the nominated target 129 * of the mountpoint 130 * - give error on symlinks 131 * - give error on ".." occurring in the path 132 * - follow traversals 133 */ 134 int nfs4_path_walk(struct nfs_server *server, 135 struct nfs_fh *mntfh, 136 const char *path) 137 { 138 struct nfs_fsinfo fsinfo; 139 struct nfs_fattr fattr; 140 struct nfs_fh lastfh; 141 struct qstr name; 142 int ret; 143 144 dprintk("--> nfs4_path_walk(,,%s)\n", path); 145 146 fsinfo.fattr = &fattr; 147 nfs_fattr_init(&fattr); 148 149 /* Eat leading slashes */ 150 while (*path == '/') 151 path++; 152 153 /* Start by getting the root filehandle from the server */ 154 ret = server->nfs_client->rpc_ops->getroot(server, mntfh, &fsinfo); 155 if (ret < 0) { 156 dprintk("nfs4_get_root: getroot error = %d\n", -ret); 157 return ret; 158 } 159 160 if (fattr.type != NFDIR) { 161 printk(KERN_ERR "nfs4_get_root:" 162 " getroot encountered non-directory\n"); 163 return -ENOTDIR; 164 } 165 166 /* FIXME: It is quite valid for the server to return a referral here */ 167 if (fattr.valid & NFS_ATTR_FATTR_V4_REFERRAL) { 168 printk(KERN_ERR "nfs4_get_root:" 169 " getroot obtained referral\n"); 170 return -EREMOTE; 171 } 172 173 next_component: 174 dprintk("Next: %s\n", path); 175 176 /* extract the next bit of the path */ 177 if (!*path) 178 goto path_walk_complete; 179 180 name.name = path; 181 while (*path && *path != '/') 182 path++; 183 name.len = path - (const char *) name.name; 184 185 if (name.len > NFS4_MAXNAMLEN) 186 return -ENAMETOOLONG; 187 188 eat_dot_dir: 189 while (*path == '/') 190 path++; 191 192 if (path[0] == '.' && (path[1] == '/' || !path[1])) { 193 path += 2; 194 goto eat_dot_dir; 195 } 196 197 /* FIXME: Why shouldn't the user be able to use ".." in the path? */ 198 if (path[0] == '.' && path[1] == '.' && (path[2] == '/' || !path[2]) 199 ) { 200 printk(KERN_ERR "nfs4_get_root:" 201 " Mount path contains reference to \"..\"\n"); 202 return -EINVAL; 203 } 204 205 /* lookup the next FH in the sequence */ 206 memcpy(&lastfh, mntfh, sizeof(lastfh)); 207 208 dprintk("LookupFH: %*.*s [%s]\n", name.len, name.len, name.name, path); 209 210 ret = server->nfs_client->rpc_ops->lookupfh(server, &lastfh, &name, 211 mntfh, &fattr); 212 if (ret < 0) { 213 dprintk("nfs4_get_root: getroot error = %d\n", -ret); 214 return ret; 215 } 216 217 if (fattr.type != NFDIR) { 218 printk(KERN_ERR "nfs4_get_root:" 219 " lookupfh encountered non-directory\n"); 220 return -ENOTDIR; 221 } 222 223 /* FIXME: Referrals are quite valid here too */ 224 if (fattr.valid & NFS_ATTR_FATTR_V4_REFERRAL) { 225 printk(KERN_ERR "nfs4_get_root:" 226 " lookupfh obtained referral\n"); 227 return -EREMOTE; 228 } 229 230 goto next_component; 231 232 path_walk_complete: 233 memcpy(&server->fsid, &fattr.fsid, sizeof(server->fsid)); 234 dprintk("<-- nfs4_path_walk() = 0\n"); 235 return 0; 236 } 237 238 /* 239 * get an NFS4 root dentry from the root filehandle 240 */ 241 struct dentry *nfs4_get_root(struct super_block *sb, struct nfs_fh *mntfh) 242 { 243 struct nfs_server *server = NFS_SB(sb); 244 struct nfs_fattr fattr; 245 struct dentry *mntroot; 246 struct inode *inode; 247 int error; 248 249 dprintk("--> nfs4_get_root()\n"); 250 251 /* get the info about the server and filesystem */ 252 error = nfs4_server_capabilities(server, mntfh); 253 if (error < 0) { 254 dprintk("nfs_get_root: getcaps error = %d\n", 255 -error); 256 return ERR_PTR(error); 257 } 258 259 /* get the actual root for this mount */ 260 error = server->nfs_client->rpc_ops->getattr(server, mntfh, &fattr); 261 if (error < 0) { 262 dprintk("nfs_get_root: getattr error = %d\n", -error); 263 return ERR_PTR(error); 264 } 265 266 inode = nfs_fhget(sb, mntfh, &fattr); 267 if (IS_ERR(inode)) { 268 dprintk("nfs_get_root: get root inode failed\n"); 269 return ERR_CAST(inode); 270 } 271 272 error = nfs_superblock_set_dummy_root(sb, inode); 273 if (error != 0) 274 return ERR_PTR(error); 275 276 /* root dentries normally start off anonymous and get spliced in later 277 * if the dentry tree reaches them; however if the dentry already 278 * exists, we'll pick it up at this point and use it as the root 279 */ 280 mntroot = d_alloc_anon(inode); 281 if (!mntroot) { 282 iput(inode); 283 dprintk("nfs_get_root: get root dentry failed\n"); 284 return ERR_PTR(-ENOMEM); 285 } 286 287 security_d_instantiate(mntroot, inode); 288 289 if (!mntroot->d_op) 290 mntroot->d_op = server->nfs_client->rpc_ops->dentry_ops; 291 292 dprintk("<-- nfs4_get_root()\n"); 293 return mntroot; 294 } 295 296 #endif /* CONFIG_NFS_V4 */ 297