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