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  * 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         return 0;
  62 }
  63
  64 /*
  65  * get an NFS2/NFS3 root dentry from the root filehandle
  66  */
  67 struct dentry *nfs_get_root(struct super_block *sb, struct nfs_fh *mntfh)
  68 {
  69         struct nfs_server *server = NFS_SB(sb);
  70         struct nfs_fsinfo fsinfo;
  71         struct nfs_fattr fattr;
  72         struct dentry *mntroot;
  73         struct inode *inode;
  74         int error;
  75
  76         /* get the actual root for this mount */
  77         fsinfo.fattr = &fattr;
  78
  79         error = server->nfs_client->rpc_ops->getroot(server, mntfh, &fsinfo);
  80         if (error < 0) {
  81                 dprintk("nfs_get_root: getattr error = %d\n", -error);
  82                 return ERR_PTR(error);
  83         }
  84
  85         inode = nfs_fhget(sb, mntfh, fsinfo.fattr);
  86         if (IS_ERR(inode)) {
  87                 dprintk("nfs_get_root: get root inode failed\n");
  88                 return ERR_PTR(PTR_ERR(inode));
  89         }
  90
  91         error = nfs_superblock_set_dummy_root(sb, inode);
  92         if (error != 0)
  93                 return ERR_PTR(error);
  94
  95         /* root dentries normally start off anonymous and get spliced in later
  96          * if the dentry tree reaches them; however if the dentry already
  97          * exists, we'll pick it up at this point and use it as the root
  98          */
  99         mntroot = d_alloc_anon(inode);
 100         if (!mntroot) {
 101                 iput(inode);
 102                 dprintk("nfs_get_root: get root dentry failed\n");
 103                 return ERR_PTR(-ENOMEM);
 104         }
 105
 106         security_d_instantiate(mntroot, inode);
 107
 108         if (!mntroot->d_op)
 109                 mntroot->d_op = server->nfs_client->rpc_ops->dentry_ops;
 110
 111         return mntroot;
 112 }
 113
 114 #ifdef CONFIG_NFS_V4
 115
 116 /*
 117  * Do a simple pathwalk from the root FH of the server to the nominated target
 118  * of the mountpoint
 119  * - give error on symlinks
 120  * - give error on ".." occurring in the path
 121  * - follow traversals
 122  */
 123 int nfs4_path_walk(struct nfs_server *server,
 124                    struct nfs_fh *mntfh,
 125                    const char *path)
 126 {
 127         struct nfs_fsinfo fsinfo;
 128         struct nfs_fattr fattr;
 129         struct nfs_fh lastfh;
 130         struct qstr name;
 131         int ret;
 132
 133         dprintk("--> nfs4_path_walk(,,%s)\n", path);
 134
 135         fsinfo.fattr = &fattr;
 136         nfs_fattr_init(&fattr);
 137
 138         /* Eat leading slashes */
 139         while (*path == '/')
 140                 path++;
 141
 142         /* Start by getting the root filehandle from the server */
 143         ret = server->nfs_client->rpc_ops->getroot(server, mntfh, &fsinfo);
 144         if (ret < 0) {
 145                 dprintk("nfs4_get_root: getroot error = %d\n", -ret);
 146                 return ret;
 147         }
 148
 149         if (fattr.type != NFDIR) {
 150                 printk(KERN_ERR "nfs4_get_root:"
 151                        " getroot encountered non-directory\n");
 152                 return -ENOTDIR;
 153         }
 154
 155         /* FIXME: It is quite valid for the server to return a referral here */
 156         if (fattr.valid & NFS_ATTR_FATTR_V4_REFERRAL) {
 157                 printk(KERN_ERR "nfs4_get_root:"
 158                        " getroot obtained referral\n");
 159                 return -EREMOTE;
 160         }
 161
 162 next_component:
 163         dprintk("Next: %s\n", path);
 164
 165         /* extract the next bit of the path */
 166         if (!*path)
 167                 goto path_walk_complete;
 168
 169         name.name = path;
 170         while (*path && *path != '/')
 171                 path++;
 172         name.len = path - (const char *) name.name;
 173
 174         if (name.len > NFS4_MAXNAMLEN)
 175                 return -ENAMETOOLONG;
 176
 177 eat_dot_dir:
 178         while (*path == '/')
 179                 path++;
 180
 181         if (path[0] == '.' && (path[1] == '/' || !path[1])) {
 182                 path += 2;
 183                 goto eat_dot_dir;
 184         }
 185
 186         /* FIXME: Why shouldn't the user be able to use ".." in the path? */
 187         if (path[0] == '.' && path[1] == '.' && (path[2] == '/' || !path[2])
 188             ) {
 189                 printk(KERN_ERR "nfs4_get_root:"
 190                        " Mount path contains reference to \"..\"\n");
 191                 return -EINVAL;
 192         }
 193
 194         /* lookup the next FH in the sequence */
 195         memcpy(&lastfh, mntfh, sizeof(lastfh));
 196
 197         dprintk("LookupFH: %*.*s [%s]\n", name.len, name.len, name.name, path);
 198
 199         ret = server->nfs_client->rpc_ops->lookupfh(server, &lastfh, &name,
 200                                                     mntfh, &fattr);
 201         if (ret < 0) {
 202                 dprintk("nfs4_get_root: getroot error = %d\n", -ret);
 203                 return ret;
 204         }
 205
 206         if (fattr.type != NFDIR) {
 207                 printk(KERN_ERR "nfs4_get_root:"
 208                        " lookupfh encountered non-directory\n");
 209                 return -ENOTDIR;
 210         }
 211
 212         /* FIXME: Referrals are quite valid here too */
 213         if (fattr.valid & NFS_ATTR_FATTR_V4_REFERRAL) {
 214                 printk(KERN_ERR "nfs4_get_root:"
 215                        " lookupfh obtained referral\n");
 216                 return -EREMOTE;
 217         }
 218
 219         goto next_component;
 220
 221 path_walk_complete:
 222         memcpy(&server->fsid, &fattr.fsid, sizeof(server->fsid));
 223         dprintk("<-- nfs4_path_walk() = 0\n");
 224         return 0;
 225 }
 226
 227 /*
 228  * get an NFS4 root dentry from the root filehandle
 229  */
 230 struct dentry *nfs4_get_root(struct super_block *sb, struct nfs_fh *mntfh)
 231 {
 232         struct nfs_server *server = NFS_SB(sb);
 233         struct nfs_fattr fattr;
 234         struct dentry *mntroot;
 235         struct inode *inode;
 236         int error;
 237
 238         dprintk("--> nfs4_get_root()\n");
 239
 240         /* get the info about the server and filesystem */
 241         error = nfs4_server_capabilities(server, mntfh);
 242         if (error < 0) {
 243                 dprintk("nfs_get_root: getcaps error = %d\n",
 244                         -error);
 245                 return ERR_PTR(error);
 246         }
 247
 248         /* get the actual root for this mount */
 249         error = server->nfs_client->rpc_ops->getattr(server, mntfh, &fattr);
 250         if (error < 0) {
 251                 dprintk("nfs_get_root: getattr error = %d\n", -error);
 252                 return ERR_PTR(error);
 253         }
 254
 255         inode = nfs_fhget(sb, mntfh, &fattr);
 256         if (IS_ERR(inode)) {
 257                 dprintk("nfs_get_root: get root inode failed\n");
 258                 return ERR_PTR(PTR_ERR(inode));
 259         }
 260
 261         error = nfs_superblock_set_dummy_root(sb, inode);
 262         if (error != 0)
 263                 return ERR_PTR(error);
 264
 265         /* root dentries normally start off anonymous and get spliced in later
 266          * if the dentry tree reaches them; however if the dentry already
 267          * exists, we'll pick it up at this point and use it as the root
 268          */
 269         mntroot = d_alloc_anon(inode);
 270         if (!mntroot) {
 271                 iput(inode);
 272                 dprintk("nfs_get_root: get root dentry failed\n");
 273                 return ERR_PTR(-ENOMEM);
 274         }
 275
 276         security_d_instantiate(mntroot, inode);
 277
 278         if (!mntroot->d_op)
 279                 mntroot->d_op = server->nfs_client->rpc_ops->dentry_ops;
 280
 281         dprintk("<-- nfs4_get_root()\n");
 282         return mntroot;
 283 }
 284
 285 #endif /* CONFIG_NFS_V4 */