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                  * 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 */