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_obtain_alias(inode); 111 if (IS_ERR(mntroot)) { 112 dprintk("nfs_get_root: get root dentry failed\n"); 113 return mntroot; 114 } 115 116 security_d_instantiate(mntroot, inode); 117 118 if (!mntroot->d_op) 119 mntroot->d_op = server->nfs_client->rpc_ops->dentry_ops; 120 121 return mntroot; 122 } 123 124 #ifdef CONFIG_NFS_V4 125 126 /* 127 * Do a simple pathwalk from the root FH of the server to the nominated target 128 * of the mountpoint 129 * - give error on symlinks 130 * - give error on ".." occurring in the path 131 * - follow traversals 132 */ 133 int nfs4_path_walk(struct nfs_server *server, 134 struct nfs_fh *mntfh, 135 const char *path) 136 { 137 struct nfs_fsinfo fsinfo; 138 struct nfs_fattr fattr; 139 struct nfs_fh lastfh; 140 struct qstr name; 141 int ret; 142 143 dprintk("--> nfs4_path_walk(,,%s)\n", path); 144 145 fsinfo.fattr = &fattr; 146 nfs_fattr_init(&fattr); 147 148 /* Eat leading slashes */ 149 while (*path == '/') 150 path++; 151 152 /* Start by getting the root filehandle from the server */ 153 ret = server->nfs_client->rpc_ops->getroot(server, mntfh, &fsinfo); 154 if (ret < 0) { 155 dprintk("nfs4_get_root: getroot error = %d\n", -ret); 156 return ret; 157 } 158 159 if (!S_ISDIR(fattr.mode)) { 160 printk(KERN_ERR "nfs4_get_root:" 161 " getroot encountered non-directory\n"); 162 return -ENOTDIR; 163 } 164 165 /* FIXME: It is quite valid for the server to return a referral here */ 166 if (fattr.valid & NFS_ATTR_FATTR_V4_REFERRAL) { 167 printk(KERN_ERR "nfs4_get_root:" 168 " getroot obtained referral\n"); 169 return -EREMOTE; 170 } 171 172 next_component: 173 dprintk("Next: %s\n", path); 174 175 /* extract the next bit of the path */ 176 if (!*path) 177 goto path_walk_complete; 178 179 name.name = path; 180 while (*path && *path != '/') 181 path++; 182 name.len = path - (const char *) name.name; 183 184 if (name.len > NFS4_MAXNAMLEN) 185 return -ENAMETOOLONG; 186 187 eat_dot_dir: 188 while (*path == '/') 189 path++; 190 191 if (path[0] == '.' && (path[1] == '/' || !path[1])) { 192 path += 2; 193 goto eat_dot_dir; 194 } 195 196 /* FIXME: Why shouldn't the user be able to use ".." in the path? */ 197 if (path[0] == '.' && path[1] == '.' && (path[2] == '/' || !path[2]) 198 ) { 199 printk(KERN_ERR "nfs4_get_root:" 200 " Mount path contains reference to \"..\"\n"); 201 return -EINVAL; 202 } 203 204 /* lookup the next FH in the sequence */ 205 memcpy(&lastfh, mntfh, sizeof(lastfh)); 206 207 dprintk("LookupFH: %*.*s [%s]\n", name.len, name.len, name.name, path); 208 209 ret = server->nfs_client->rpc_ops->lookupfh(server, &lastfh, &name, 210 mntfh, &fattr); 211 if (ret < 0) { 212 dprintk("nfs4_get_root: getroot error = %d\n", -ret); 213 return ret; 214 } 215 216 if (!S_ISDIR(fattr.mode)) { 217 printk(KERN_ERR "nfs4_get_root:" 218 " lookupfh encountered non-directory\n"); 219 return -ENOTDIR; 220 } 221 222 /* FIXME: Referrals are quite valid here too */ 223 if (fattr.valid & NFS_ATTR_FATTR_V4_REFERRAL) { 224 printk(KERN_ERR "nfs4_get_root:" 225 " lookupfh obtained referral\n"); 226 return -EREMOTE; 227 } 228 229 goto next_component; 230 231 path_walk_complete: 232 memcpy(&server->fsid, &fattr.fsid, sizeof(server->fsid)); 233 dprintk("<-- nfs4_path_walk() = 0\n"); 234 return 0; 235 } 236 237 /* 238 * get an NFS4 root dentry from the root filehandle 239 */ 240 struct dentry *nfs4_get_root(struct super_block *sb, struct nfs_fh *mntfh) 241 { 242 struct nfs_server *server = NFS_SB(sb); 243 struct nfs_fattr fattr; 244 struct dentry *mntroot; 245 struct inode *inode; 246 int error; 247 248 dprintk("--> nfs4_get_root()\n"); 249 250 /* get the info about the server and filesystem */ 251 error = nfs4_server_capabilities(server, mntfh); 252 if (error < 0) { 253 dprintk("nfs_get_root: getcaps error = %d\n", 254 -error); 255 return ERR_PTR(error); 256 } 257 258 /* get the actual root for this mount */ 259 error = server->nfs_client->rpc_ops->getattr(server, mntfh, &fattr); 260 if (error < 0) { 261 dprintk("nfs_get_root: getattr error = %d\n", -error); 262 return ERR_PTR(error); 263 } 264 265 inode = nfs_fhget(sb, mntfh, &fattr); 266 if (IS_ERR(inode)) { 267 dprintk("nfs_get_root: get root inode failed\n"); 268 return ERR_CAST(inode); 269 } 270 271 error = nfs_superblock_set_dummy_root(sb, inode); 272 if (error != 0) 273 return ERR_PTR(error); 274 275 /* root dentries normally start off anonymous and get spliced in later 276 * if the dentry tree reaches them; however if the dentry already 277 * exists, we'll pick it up at this point and use it as the root 278 */ 279 mntroot = d_obtain_alias(inode); 280 if (IS_ERR(mntroot)) { 281 dprintk("nfs_get_root: get root dentry failed\n"); 282 return mntroot; 283 } 284 285 security_d_instantiate(mntroot, inode); 286 287 if (!mntroot->d_op) 288 mntroot->d_op = server->nfs_client->rpc_ops->dentry_ops; 289 290 dprintk("<-- nfs4_get_root()\n"); 291 return mntroot; 292 } 293 294 #endif /* CONFIG_NFS_V4 */ 295