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/security.h>
  34
  35 #include <asm/system.h>
  36 #include <asm/uaccess.h>
  37
  38 #include "nfs4_fs.h"
  39 #include "delegation.h"
  40 #include "internal.h"
  41
  42 #define NFSDBG_FACILITY         NFSDBG_CLIENT
  43
  44 /*
  45  * Set the superblock root dentry.
  46  * Note that this function frees the inode in case of error.
  47  */
  48 static int nfs_superblock_set_dummy_root(struct super_block *sb, struct inode *inode)
  49 {
  50         /* The mntroot acts as the dummy root dentry for this superblock */
  51         if (sb->s_root == NULL) {
  52                 sb->s_root = d_alloc_root(inode);
  53                 if (sb->s_root == NULL) {
  54                         iput(inode);
  55                         return -ENOMEM;
  56                 }
  57                 /* Circumvent igrab(): we know the inode is not being freed */
  58                 atomic_inc(&inode->i_count);
  59                 /*
  60                  * Ensure that this dentry is invisible to d_find_alias().
  61                  * Otherwise, it may be spliced into the tree by
  62                  * d_materialise_unique if a parent directory from the same
  63                  * filesystem gets mounted at a later time.
  64                  * This again causes shrink_dcache_for_umount_subtree() to
  65                  * Oops, since the test for IS_ROOT() will fail.
  66                  */
  67                 spin_lock(&dcache_lock);
  68                 list_del_init(&sb->s_root->d_alias);
  69                 spin_unlock(&dcache_lock);
  70         }
  71         return 0;
  72 }
  73
  74 /*
  75  * get an NFS2/NFS3 root dentry from the root filehandle
  76  */
  77 struct dentry *nfs_get_root(struct super_block *sb, struct nfs_fh *mntfh)
  78 {
  79         struct nfs_server *server = NFS_SB(sb);
  80         struct nfs_fsinfo fsinfo;
  81         struct nfs_fattr fattr;
  82         struct dentry *mntroot;
  83         struct inode *inode;
  84         int error;
  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_CAST(inode);
  99         }
 100
 101         error = nfs_superblock_set_dummy_root(sb, inode);
 102         if (error != 0)
 103                 return ERR_PTR(error);
 104
 105         /* root dentries normally start off anonymous and get spliced in later
 106          * if the dentry tree reaches them; however if the dentry already
 107          * exists, we'll pick it up at this point and use it as the root
 108          */
 109         mntroot = d_obtain_alias(inode);
 110         if (IS_ERR(mntroot)) {
 111                 dprintk("nfs_get_root: get root dentry failed\n");
 112                 return mntroot;
 113         }
 114
 115         security_d_instantiate(mntroot, inode);
 116
 117         if (!mntroot->d_op)
 118                 mntroot->d_op = server->nfs_client->rpc_ops->dentry_ops;
 119
 120         return mntroot;
 121 }
 122
 123 #ifdef CONFIG_NFS_V4
 124
 125 /*
 126  * Do a simple pathwalk from the root FH of the server to the nominated target
 127  * of the mountpoint
 128  * - give error on symlinks
 129  * - give error on ".." occurring in the path
 130  * - follow traversals
 131  */
 132 int nfs4_path_walk(struct nfs_server *server,
 133                    struct nfs_fh *mntfh,
 134                    const char *path)
 135 {
 136         struct nfs_fsinfo fsinfo;
 137         struct nfs_fattr fattr;
 138         struct nfs_fh lastfh;
 139         struct qstr name;
 140         int ret;
 141
 142         dprintk("--> nfs4_path_walk(,,%s)\n", path);
 143
 144         fsinfo.fattr = &fattr;
 145         nfs_fattr_init(&fattr);
 146
 147         /* Eat leading slashes */
 148         while (*path == '/')
 149                 path++;
 150
 151         /* Start by getting the root filehandle from the server */
 152         ret = server->nfs_client->rpc_ops->getroot(server, mntfh, &fsinfo);
 153         if (ret < 0) {
 154                 dprintk("nfs4_get_root: getroot error = %d\n", -ret);
 155                 return ret;
 156         }
 157
 158         if (!S_ISDIR(fattr.mode)) {
 159                 printk(KERN_ERR "nfs4_get_root:"
 160                        " getroot encountered non-directory\n");
 161                 return -ENOTDIR;
 162         }
 163
 164         /* FIXME: It is quite valid for the server to return a referral here */
 165         if (fattr.valid & NFS_ATTR_FATTR_V4_REFERRAL) {
 166                 printk(KERN_ERR "nfs4_get_root:"
 167                        " getroot obtained referral\n");
 168                 return -EREMOTE;
 169         }
 170
 171 next_component:
 172         dprintk("Next: %s\n", path);
 173
 174         /* extract the next bit of the path */
 175         if (!*path)
 176                 goto path_walk_complete;
 177
 178         name.name = path;
 179         while (*path && *path != '/')
 180                 path++;
 181         name.len = path - (const char *) name.name;
 182
 183         if (name.len > NFS4_MAXNAMLEN)
 184                 return -ENAMETOOLONG;
 185
 186 eat_dot_dir:
 187         while (*path == '/')
 188                 path++;
 189
 190         if (path[0] == '.' && (path[1] == '/' || !path[1])) {
 191                 path += 2;
 192                 goto eat_dot_dir;
 193         }
 194
 195         /* FIXME: Why shouldn't the user be able to use ".." in the path? */
 196         if (path[0] == '.' && path[1] == '.' && (path[2] == '/' || !path[2])
 197             ) {
 198                 printk(KERN_ERR "nfs4_get_root:"
 199                        " Mount path contains reference to \"..\"\n");
 200                 return -EINVAL;
 201         }
 202
 203         /* lookup the next FH in the sequence */
 204         memcpy(&lastfh, mntfh, sizeof(lastfh));
 205
 206         dprintk("LookupFH: %*.*s [%s]\n", name.len, name.len, name.name, path);
 207
 208         ret = server->nfs_client->rpc_ops->lookupfh(server, &lastfh, &name,
 209                                                     mntfh, &fattr);
 210         if (ret < 0) {
 211                 dprintk("nfs4_get_root: getroot error = %d\n", -ret);
 212                 return ret;
 213         }
 214
 215         if (!S_ISDIR(fattr.mode)) {
 216                 printk(KERN_ERR "nfs4_get_root:"
 217                        " lookupfh encountered non-directory\n");
 218                 return -ENOTDIR;
 219         }
 220
 221         /* FIXME: Referrals are quite valid here too */
 222         if (fattr.valid & NFS_ATTR_FATTR_V4_REFERRAL) {
 223                 printk(KERN_ERR "nfs4_get_root:"
 224                        " lookupfh obtained referral\n");
 225                 return -EREMOTE;
 226         }
 227
 228         goto next_component;
 229
 230 path_walk_complete:
 231         memcpy(&server->fsid, &fattr.fsid, sizeof(server->fsid));
 232         dprintk("<-- nfs4_path_walk() = 0\n");
 233         return 0;
 234 }
 235
 236 /*
 237  * get an NFS4 root dentry from the root filehandle
 238  */
 239 struct dentry *nfs4_get_root(struct super_block *sb, struct nfs_fh *mntfh)
 240 {
 241         struct nfs_server *server = NFS_SB(sb);
 242         struct nfs_fattr fattr;
 243         struct dentry *mntroot;
 244         struct inode *inode;
 245         int error;
 246
 247         dprintk("--> nfs4_get_root()\n");
 248
 249         /* get the info about the server and filesystem */
 250         error = nfs4_server_capabilities(server, mntfh);
 251         if (error < 0) {
 252                 dprintk("nfs_get_root: getcaps error = %d\n",
 253                         -error);
 254                 return ERR_PTR(error);
 255         }
 256
 257         /* get the actual root for this mount */
 258         error = server->nfs_client->rpc_ops->getattr(server, mntfh, &fattr);
 259         if (error < 0) {
 260                 dprintk("nfs_get_root: getattr error = %d\n", -error);
 261                 return ERR_PTR(error);
 262         }
 263
 264         inode = nfs_fhget(sb, mntfh, &fattr);
 265         if (IS_ERR(inode)) {
 266                 dprintk("nfs_get_root: get root inode failed\n");
 267                 return ERR_CAST(inode);
 268         }
 269
 270         error = nfs_superblock_set_dummy_root(sb, inode);
 271         if (error != 0)
 272                 return ERR_PTR(error);
 273
 274         /* root dentries normally start off anonymous and get spliced in later
 275          * if the dentry tree reaches them; however if the dentry already
 276          * exists, we'll pick it up at this point and use it as the root
 277          */
 278         mntroot = d_obtain_alias(inode);
 279         if (IS_ERR(mntroot)) {
 280                 dprintk("nfs_get_root: get root dentry failed\n");
 281                 return mntroot;
 282         }
 283
 284         security_d_instantiate(mntroot, inode);
 285
 286         if (!mntroot->d_op)
 287                 mntroot->d_op = server->nfs_client->rpc_ops->dentry_ops;
 288
 289         dprintk("<-- nfs4_get_root()\n");
 290         return mntroot;
 291 }
 292
 293 #endif /* CONFIG_NFS_V4 */