fs/nfs/getroot.c

   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  * get an NFS2/NFS3 root dentry from the root filehandle
  47  */
  48 struct dentry *nfs_get_root(struct super_block *sb, struct nfs_fh *mntfh)
  49 {
  50         struct nfs_server *server = NFS_SB(sb);
  51         struct nfs_fsinfo fsinfo;
  52         struct nfs_fattr fattr;
  53         struct dentry *mntroot;
  54         struct inode *inode;
  55         int error;
  56
  57         /* create a dummy root dentry with dummy inode for this superblock */
  58         if (!sb->s_root) {
  59                 struct nfs_fh dummyfh;
  60                 struct dentry *root;
  61                 struct inode *iroot;
  62
  63                 memset(&dummyfh, 0, sizeof(dummyfh));
  64                 memset(&fattr, 0, sizeof(fattr));
  65                 nfs_fattr_init(&fattr);
  66                 fattr.valid = NFS_ATTR_FATTR;
  67                 fattr.type = NFDIR;
  68                 fattr.mode = S_IFDIR | S_IRUSR | S_IWUSR;
  69                 fattr.nlink = 2;
  70
  71                 iroot = nfs_fhget(sb, &dummyfh, &fattr);
  72                 if (IS_ERR(iroot))
  73                         return ERR_PTR(PTR_ERR(iroot));
  74
  75                 root = d_alloc_root(iroot);
  76                 if (!root) {
  77                         iput(iroot);
  78                         return ERR_PTR(-ENOMEM);
  79                 }
  80
  81                 sb->s_root = root;
  82         }
  83
  84         /* get the actual root for this mount */
  85         fsinfo.fattr = &fattr;
  86
  87         error = server->nfs_client->rpc_ops->getroot(server, mntfh, &fsinfo);
  88         if (error < 0) {
  89                 dprintk("nfs_get_root: getattr error = %d\n", -error);
  90                 return ERR_PTR(error);
  91         }
  92
  93         inode = nfs_fhget(sb, mntfh, fsinfo.fattr);
  94         if (IS_ERR(inode)) {
  95                 dprintk("nfs_get_root: get root inode failed\n");
  96                 return ERR_PTR(PTR_ERR(inode));
  97         }
  98
  99         /* root dentries normally start off anonymous and get spliced in later
 100          * if the dentry tree reaches them; however if the dentry already
 101          * exists, we'll pick it up at this point and use it as the root
 102          */
 103         mntroot = d_alloc_anon(inode);
 104         if (!mntroot) {
 105                 iput(inode);
 106                 dprintk("nfs_get_root: get root dentry failed\n");
 107                 return ERR_PTR(-ENOMEM);
 108         }
 109
 110         security_d_instantiate(mntroot, inode);
 111
 112         if (!mntroot->d_op)
 113                 mntroot->d_op = server->nfs_client->rpc_ops->dentry_ops;
 114
 115         return mntroot;
 116 }
 117
 118 #ifdef CONFIG_NFS_V4
 119
 120 /*
 121  * Do a simple pathwalk from the root FH of the server to the nominated target
 122  * of the mountpoint
 123  * - give error on symlinks
 124  * - give error on ".." occurring in the path
 125  * - follow traversals
 126  */
 127 int nfs4_path_walk(struct nfs_server *server,
 128                    struct nfs_fh *mntfh,
 129                    const char *path)
 130 {
 131         struct nfs_fsinfo fsinfo;
 132         struct nfs_fattr fattr;
 133         struct nfs_fh lastfh;
 134         struct qstr name;
 135         int ret;
 136
 137         dprintk("--> nfs4_path_walk(,,%s)\n", path);
 138
 139         fsinfo.fattr = &fattr;
 140         nfs_fattr_init(&fattr);
 141
 142         /* Eat leading slashes */
 143         while (*path == '/')
 144                 path++;
 145
 146         /* Start by getting the root filehandle from the server */
 147         ret = server->nfs_client->rpc_ops->getroot(server, mntfh, &fsinfo);
 148         if (ret < 0) {
 149                 dprintk("nfs4_get_root: getroot error = %d\n", -ret);
 150                 return ret;
 151         }
 152
 153         if (fattr.type != NFDIR) {
 154                 printk(KERN_ERR "nfs4_get_root:"
 155                        " getroot encountered non-directory\n");
 156                 return -ENOTDIR;
 157         }
 158
 159         /* FIXME: It is quite valid for the server to return a referral here */
 160         if (fattr.valid & NFS_ATTR_FATTR_V4_REFERRAL) {
 161                 printk(KERN_ERR "nfs4_get_root:"
 162                        " getroot obtained referral\n");
 163                 return -EREMOTE;
 164         }
 165
 166 next_component:
 167         dprintk("Next: %s\n", path);
 168
 169         /* extract the next bit of the path */
 170         if (!*path)
 171                 goto path_walk_complete;
 172
 173         name.name = path;
 174         while (*path && *path != '/')
 175                 path++;
 176         name.len = path - (const char *) name.name;
 177
 178 eat_dot_dir:
 179         while (*path == '/')
 180                 path++;
 181
 182         if (path[0] == '.' && (path[1] == '/' || !path[1])) {
 183                 path += 2;
 184                 goto eat_dot_dir;
 185         }
 186
 187         /* FIXME: Why shouldn't the user be able to use ".." in the path? */
 188         if (path[0] == '.' && path[1] == '.' && (path[2] == '/' || !path[2])
 189             ) {
 190                 printk(KERN_ERR "nfs4_get_root:"
 191                        " Mount path contains reference to \"..\"\n");
 192                 return -EINVAL;
 193         }
 194
 195         /* lookup the next FH in the sequence */
 196         memcpy(&lastfh, mntfh, sizeof(lastfh));
 197
 198         dprintk("LookupFH: %*.*s [%s]\n", name.len, name.len, name.name, path);
 199
 200         ret = server->nfs_client->rpc_ops->lookupfh(server, &lastfh, &name,
 201                                                     mntfh, &fattr);
 202         if (ret < 0) {
 203                 dprintk("nfs4_get_root: getroot error = %d\n", -ret);
 204                 return ret;
 205         }
 206
 207         if (fattr.type != NFDIR) {
 208                 printk(KERN_ERR "nfs4_get_root:"
 209                        " lookupfh encountered non-directory\n");
 210                 return -ENOTDIR;
 211         }
 212
 213         /* FIXME: Referrals are quite valid here too */
 214         if (fattr.valid & NFS_ATTR_FATTR_V4_REFERRAL) {
 215                 printk(KERN_ERR "nfs4_get_root:"
 216                        " lookupfh obtained referral\n");
 217                 return -EREMOTE;
 218         }
 219
 220         goto next_component;
 221
 222 path_walk_complete:
 223         memcpy(&server->fsid, &fattr.fsid, sizeof(server->fsid));
 224         dprintk("<-- nfs4_path_walk() = 0\n");
 225         return 0;
 226 }
 227
 228 /*
 229  * get an NFS4 root dentry from the root filehandle
 230  */
 231 struct dentry *nfs4_get_root(struct super_block *sb, struct nfs_fh *mntfh)
 232 {
 233         struct nfs_server *server = NFS_SB(sb);
 234         struct nfs_fattr fattr;
 235         struct dentry *mntroot;
 236         struct inode *inode;
 237         int error;
 238
 239         dprintk("--> nfs4_get_root()\n");
 240
 241         /* create a dummy root dentry with dummy inode for this superblock */
 242         if (!sb->s_root) {
 243                 struct nfs_fh dummyfh;
 244                 struct dentry *root;
 245                 struct inode *iroot;
 246
 247                 memset(&dummyfh, 0, sizeof(dummyfh));
 248                 memset(&fattr, 0, sizeof(fattr));
 249                 nfs_fattr_init(&fattr);
 250                 fattr.valid = NFS_ATTR_FATTR;
 251                 fattr.type = NFDIR;
 252                 fattr.mode = S_IFDIR | S_IRUSR | S_IWUSR;
 253                 fattr.nlink = 2;
 254
 255                 iroot = nfs_fhget(sb, &dummyfh, &fattr);
 256                 if (IS_ERR(iroot))
 257                         return ERR_PTR(PTR_ERR(iroot));
 258
 259                 root = d_alloc_root(iroot);
 260                 if (!root) {
 261                         iput(iroot);
 262                         return ERR_PTR(-ENOMEM);
 263                 }
 264
 265                 sb->s_root = root;
 266         }
 267
 268         /* get the info about the server and filesystem */
 269         error = nfs4_server_capabilities(server, mntfh);
 270         if (error < 0) {
 271                 dprintk("nfs_get_root: getcaps error = %d\n",
 272                         -error);
 273                 return ERR_PTR(error);
 274         }
 275
 276         /* get the actual root for this mount */
 277         error = server->nfs_client->rpc_ops->getattr(server, mntfh, &fattr);
 278         if (error < 0) {
 279                 dprintk("nfs_get_root: getattr error = %d\n", -error);
 280                 return ERR_PTR(error);
 281         }
 282
 283         inode = nfs_fhget(sb, mntfh, &fattr);
 284         if (IS_ERR(inode)) {
 285                 dprintk("nfs_get_root: get root inode failed\n");
 286                 return ERR_PTR(PTR_ERR(inode));
 287         }
 288
 289         /* root dentries normally start off anonymous and get spliced in later
 290          * if the dentry tree reaches them; however if the dentry already
 291          * exists, we'll pick it up at this point and use it as the root
 292          */
 293         mntroot = d_alloc_anon(inode);
 294         if (!mntroot) {
 295                 iput(inode);
 296                 dprintk("nfs_get_root: get root dentry failed\n");
 297                 return ERR_PTR(-ENOMEM);
 298         }
 299
 300         security_d_instantiate(mntroot, inode);
 301
 302         if (!mntroot->d_op)
 303                 mntroot->d_op = server->nfs_client->rpc_ops->dentry_ops;
 304
 305         dprintk("<-- nfs4_get_root()\n");
 306         return mntroot;
 307 }
 308
 309 #endif /* CONFIG_NFS_V4 */