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/smp_lock.h>
  29 #include <linux/seq_file.h>
  30 #include <linux/mount.h>
  31 #include <linux/nfs_idmap.h>
  32 #include <linux/vfs.h>
  33 #include <linux/namei.h>
  34 #include <linux/mnt_namespace.h>
  35 #include <linux/security.h>
  36
  37 #include <asm/system.h>
  38 #include <asm/uaccess.h>
  39
  40 #include "nfs4_fs.h"
  41 #include "delegation.h"
  42 #include "internal.h"
  43
  44 #define NFSDBG_FACILITY         NFSDBG_CLIENT
  45 #define NFS_PARANOIA 1
  46
  47 /*
  48  * get an NFS2/NFS3 root dentry from the root filehandle
  49  */
  50 struct dentry *nfs_get_root(struct super_block *sb, struct nfs_fh *mntfh)
  51 {
  52         struct nfs_server *server = NFS_SB(sb);
  53         struct nfs_fsinfo fsinfo;
  54         struct nfs_fattr fattr;
  55         struct dentry *mntroot;
  56         struct inode *inode;
  57         int error;
  58
  59         /* create a dummy root dentry with dummy inode for this superblock */
  60         if (!sb->s_root) {
  61                 struct nfs_fh dummyfh;
  62                 struct dentry *root;
  63                 struct inode *iroot;
  64
  65                 memset(&dummyfh, 0, sizeof(dummyfh));
  66                 memset(&fattr, 0, sizeof(fattr));
  67                 nfs_fattr_init(&fattr);
  68                 fattr.valid = NFS_ATTR_FATTR;
  69                 fattr.type = NFDIR;
  70                 fattr.mode = S_IFDIR | S_IRUSR | S_IWUSR;
  71                 fattr.nlink = 2;
  72
  73                 iroot = nfs_fhget(sb, &dummyfh, &fattr);
  74                 if (IS_ERR(iroot))
  75                         return ERR_PTR(PTR_ERR(iroot));
  76
  77                 root = d_alloc_root(iroot);
  78                 if (!root) {
  79                         iput(iroot);
  80                         return ERR_PTR(-ENOMEM);
  81                 }
  82
  83                 sb->s_root = root;
  84         }
  85
  86         /* get the actual root for this mount */
  87         fsinfo.fattr = &fattr;
  88
  89         error = server->nfs_client->rpc_ops->getroot(server, mntfh, &fsinfo);
  90         if (error < 0) {
  91                 dprintk("nfs_get_root: getattr error = %d\n", -error);
  92                 return ERR_PTR(error);
  93         }
  94
  95         inode = nfs_fhget(sb, mntfh, fsinfo.fattr);
  96         if (IS_ERR(inode)) {
  97                 dprintk("nfs_get_root: get root inode failed\n");
  98                 return ERR_PTR(PTR_ERR(inode));
  99         }
 100
 101         /* root dentries normally start off anonymous and get spliced in later
 102          * if the dentry tree reaches them; however if the dentry already
 103          * exists, we'll pick it up at this point and use it as the root
 104          */
 105         mntroot = d_alloc_anon(inode);
 106         if (!mntroot) {
 107                 iput(inode);
 108                 dprintk("nfs_get_root: get root dentry failed\n");
 109                 return ERR_PTR(-ENOMEM);
 110         }
 111
 112         security_d_instantiate(mntroot, inode);
 113
 114         if (!mntroot->d_op)
 115                 mntroot->d_op = server->nfs_client->rpc_ops->dentry_ops;
 116
 117         return mntroot;
 118 }
 119
 120 #ifdef CONFIG_NFS_V4
 121
 122 /*
 123  * Do a simple pathwalk from the root FH of the server to the nominated target
 124  * of the mountpoint
 125  * - give error on symlinks
 126  * - give error on ".." occurring in the path
 127  * - follow traversals
 128  */
 129 int nfs4_path_walk(struct nfs_server *server,
 130                    struct nfs_fh *mntfh,
 131                    const char *path)
 132 {
 133         struct nfs_fsinfo fsinfo;
 134         struct nfs_fattr fattr;
 135         struct nfs_fh lastfh;
 136         struct qstr name;
 137         int ret;
 138
 139         dprintk("--> nfs4_path_walk(,,%s)\n", path);
 140
 141         fsinfo.fattr = &fattr;
 142         nfs_fattr_init(&fattr);
 143
 144         /* Eat leading slashes */
 145         while (*path == '/')
 146                 path++;
 147
 148         /* Start by getting the root filehandle from the server */
 149         ret = server->nfs_client->rpc_ops->getroot(server, mntfh, &fsinfo);
 150         if (ret < 0) {
 151                 dprintk("nfs4_get_root: getroot error = %d\n", -ret);
 152                 return ret;
 153         }
 154
 155         if (fattr.type != NFDIR) {
 156                 printk(KERN_ERR "nfs4_get_root:"
 157                        " getroot encountered non-directory\n");
 158                 return -ENOTDIR;
 159         }
 160
 161         /* FIXME: It is quite valid for the server to return a referral here */
 162         if (fattr.valid & NFS_ATTR_FATTR_V4_REFERRAL) {
 163                 printk(KERN_ERR "nfs4_get_root:"
 164                        " getroot obtained referral\n");
 165                 return -EREMOTE;
 166         }
 167
 168 next_component:
 169         dprintk("Next: %s\n", path);
 170
 171         /* extract the next bit of the path */
 172         if (!*path)
 173                 goto path_walk_complete;
 174
 175         name.name = path;
 176         while (*path && *path != '/')
 177                 path++;
 178         name.len = path - (const char *) name.name;
 179
 180 eat_dot_dir:
 181         while (*path == '/')
 182                 path++;
 183
 184         if (path[0] == '.' && (path[1] == '/' || !path[1])) {
 185                 path += 2;
 186                 goto eat_dot_dir;
 187         }
 188
 189         /* FIXME: Why shouldn't the user be able to use ".." in the path? */
 190         if (path[0] == '.' && path[1] == '.' && (path[2] == '/' || !path[2])
 191             ) {
 192                 printk(KERN_ERR "nfs4_get_root:"
 193                        " Mount path contains reference to \"..\"\n");
 194                 return -EINVAL;
 195         }
 196
 197         /* lookup the next FH in the sequence */
 198         memcpy(&lastfh, mntfh, sizeof(lastfh));
 199
 200         dprintk("LookupFH: %*.*s [%s]\n", name.len, name.len, name.name, path);
 201
 202         ret = server->nfs_client->rpc_ops->lookupfh(server, &lastfh, &name,
 203                                                     mntfh, &fattr);
 204         if (ret < 0) {
 205                 dprintk("nfs4_get_root: getroot error = %d\n", -ret);
 206                 return ret;
 207         }
 208
 209         if (fattr.type != NFDIR) {
 210                 printk(KERN_ERR "nfs4_get_root:"
 211                        " lookupfh encountered non-directory\n");
 212                 return -ENOTDIR;
 213         }
 214
 215         /* FIXME: Referrals are quite valid here too */
 216         if (fattr.valid & NFS_ATTR_FATTR_V4_REFERRAL) {
 217                 printk(KERN_ERR "nfs4_get_root:"
 218                        " lookupfh obtained referral\n");
 219                 return -EREMOTE;
 220         }
 221
 222         goto next_component;
 223
 224 path_walk_complete:
 225         memcpy(&server->fsid, &fattr.fsid, sizeof(server->fsid));
 226         dprintk("<-- nfs4_path_walk() = 0\n");
 227         return 0;
 228 }
 229
 230 /*
 231  * get an NFS4 root dentry from the root filehandle
 232  */
 233 struct dentry *nfs4_get_root(struct super_block *sb, struct nfs_fh *mntfh)
 234 {
 235         struct nfs_server *server = NFS_SB(sb);
 236         struct nfs_fattr fattr;
 237         struct dentry *mntroot;
 238         struct inode *inode;
 239         int error;
 240
 241         dprintk("--> nfs4_get_root()\n");
 242
 243         /* create a dummy root dentry with dummy inode for this superblock */
 244         if (!sb->s_root) {
 245                 struct nfs_fh dummyfh;
 246                 struct dentry *root;
 247                 struct inode *iroot;
 248
 249                 memset(&dummyfh, 0, sizeof(dummyfh));
 250                 memset(&fattr, 0, sizeof(fattr));
 251                 nfs_fattr_init(&fattr);
 252                 fattr.valid = NFS_ATTR_FATTR;
 253                 fattr.type = NFDIR;
 254                 fattr.mode = S_IFDIR | S_IRUSR | S_IWUSR;
 255                 fattr.nlink = 2;
 256
 257                 iroot = nfs_fhget(sb, &dummyfh, &fattr);
 258                 if (IS_ERR(iroot))
 259                         return ERR_PTR(PTR_ERR(iroot));
 260
 261                 root = d_alloc_root(iroot);
 262                 if (!root) {
 263                         iput(iroot);
 264                         return ERR_PTR(-ENOMEM);
 265                 }
 266
 267                 sb->s_root = root;
 268         }
 269
 270         /* get the info about the server and filesystem */
 271         error = nfs4_server_capabilities(server, mntfh);
 272         if (error < 0) {
 273                 dprintk("nfs_get_root: getcaps error = %d\n",
 274                         -error);
 275                 return ERR_PTR(error);
 276         }
 277
 278         /* get the actual root for this mount */
 279         error = server->nfs_client->rpc_ops->getattr(server, mntfh, &fattr);
 280         if (error < 0) {
 281                 dprintk("nfs_get_root: getattr error = %d\n", -error);
 282                 return ERR_PTR(error);
 283         }
 284
 285         inode = nfs_fhget(sb, mntfh, &fattr);
 286         if (IS_ERR(inode)) {
 287                 dprintk("nfs_get_root: get root inode failed\n");
 288                 return ERR_PTR(PTR_ERR(inode));
 289         }
 290
 291         /* root dentries normally start off anonymous and get spliced in later
 292          * if the dentry tree reaches them; however if the dentry already
 293          * exists, we'll pick it up at this point and use it as the root
 294          */
 295         mntroot = d_alloc_anon(inode);
 296         if (!mntroot) {
 297                 iput(inode);
 298                 dprintk("nfs_get_root: get root dentry failed\n");
 299                 return ERR_PTR(-ENOMEM);
 300         }
 301
 302         security_d_instantiate(mntroot, inode);
 303
 304         if (!mntroot->d_op)
 305                 mntroot->d_op = server->nfs_client->rpc_ops->dentry_ops;
 306
 307         dprintk("<-- nfs4_get_root()\n");
 308         return mntroot;
 309 }
 310
 311 #endif /* CONFIG_NFS_V4 */