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_alloc_anon(inode);
 111         if (!mntroot) {
 112                 iput(inode);
 113                 dprintk("nfs_get_root: get root dentry failed\n");
 114                 return ERR_PTR(-ENOMEM);
 115         }
 116
 117         security_d_instantiate(mntroot, inode);
 118
 119         if (!mntroot->d_op)
 120                 mntroot->d_op = server->nfs_client->rpc_ops->dentry_ops;
 121
 122         return mntroot;
 123 }
 124
 125 #ifdef CONFIG_NFS_V4
 126
 127 /*
 128  * Do a simple pathwalk from the root FH of the server to the nominated target
 129  * of the mountpoint
 130  * - give error on symlinks
 131  * - give error on ".." occurring in the path
 132  * - follow traversals
 133  */
 134 int nfs4_path_walk(struct nfs_server *server,
 135                    struct nfs_fh *mntfh,
 136                    const char *path)
 137 {
 138         struct nfs_fsinfo fsinfo;
 139         struct nfs_fattr fattr;
 140         struct nfs_fh lastfh;
 141         struct qstr name;
 142         int ret;
 143
 144         dprintk("--> nfs4_path_walk(,,%s)\n", path);
 145
 146         fsinfo.fattr = &fattr;
 147         nfs_fattr_init(&fattr);
 148
 149         /* Eat leading slashes */
 150         while (*path == '/')
 151                 path++;
 152
 153         /* Start by getting the root filehandle from the server */
 154         ret = server->nfs_client->rpc_ops->getroot(server, mntfh, &fsinfo);
 155         if (ret < 0) {
 156                 dprintk("nfs4_get_root: getroot error = %d\n", -ret);
 157                 return ret;
 158         }
 159
 160         if (fattr.type != NFDIR) {
 161                 printk(KERN_ERR "nfs4_get_root:"
 162                        " getroot encountered non-directory\n");
 163                 return -ENOTDIR;
 164         }
 165
 166         /* FIXME: It is quite valid for the server to return a referral here */
 167         if (fattr.valid & NFS_ATTR_FATTR_V4_REFERRAL) {
 168                 printk(KERN_ERR "nfs4_get_root:"
 169                        " getroot obtained referral\n");
 170                 return -EREMOTE;
 171         }
 172
 173 next_component:
 174         dprintk("Next: %s\n", path);
 175
 176         /* extract the next bit of the path */
 177         if (!*path)
 178                 goto path_walk_complete;
 179
 180         name.name = path;
 181         while (*path && *path != '/')
 182                 path++;
 183         name.len = path - (const char *) name.name;
 184
 185         if (name.len > NFS4_MAXNAMLEN)
 186                 return -ENAMETOOLONG;
 187
 188 eat_dot_dir:
 189         while (*path == '/')
 190                 path++;
 191
 192         if (path[0] == '.' && (path[1] == '/' || !path[1])) {
 193                 path += 2;
 194                 goto eat_dot_dir;
 195         }
 196
 197         /* FIXME: Why shouldn't the user be able to use ".." in the path? */
 198         if (path[0] == '.' && path[1] == '.' && (path[2] == '/' || !path[2])
 199             ) {
 200                 printk(KERN_ERR "nfs4_get_root:"
 201                        " Mount path contains reference to \"..\"\n");
 202                 return -EINVAL;
 203         }
 204
 205         /* lookup the next FH in the sequence */
 206         memcpy(&lastfh, mntfh, sizeof(lastfh));
 207
 208         dprintk("LookupFH: %*.*s [%s]\n", name.len, name.len, name.name, path);
 209
 210         ret = server->nfs_client->rpc_ops->lookupfh(server, &lastfh, &name,
 211                                                     mntfh, &fattr);
 212         if (ret < 0) {
 213                 dprintk("nfs4_get_root: getroot error = %d\n", -ret);
 214                 return ret;
 215         }
 216
 217         if (fattr.type != NFDIR) {
 218                 printk(KERN_ERR "nfs4_get_root:"
 219                        " lookupfh encountered non-directory\n");
 220                 return -ENOTDIR;
 221         }
 222
 223         /* FIXME: Referrals are quite valid here too */
 224         if (fattr.valid & NFS_ATTR_FATTR_V4_REFERRAL) {
 225                 printk(KERN_ERR "nfs4_get_root:"
 226                        " lookupfh obtained referral\n");
 227                 return -EREMOTE;
 228         }
 229
 230         goto next_component;
 231
 232 path_walk_complete:
 233         memcpy(&server->fsid, &fattr.fsid, sizeof(server->fsid));
 234         dprintk("<-- nfs4_path_walk() = 0\n");
 235         return 0;
 236 }
 237
 238 /*
 239  * get an NFS4 root dentry from the root filehandle
 240  */
 241 struct dentry *nfs4_get_root(struct super_block *sb, struct nfs_fh *mntfh)
 242 {
 243         struct nfs_server *server = NFS_SB(sb);
 244         struct nfs_fattr fattr;
 245         struct dentry *mntroot;
 246         struct inode *inode;
 247         int error;
 248
 249         dprintk("--> nfs4_get_root()\n");
 250
 251         /* get the info about the server and filesystem */
 252         error = nfs4_server_capabilities(server, mntfh);
 253         if (error < 0) {
 254                 dprintk("nfs_get_root: getcaps error = %d\n",
 255                         -error);
 256                 return ERR_PTR(error);
 257         }
 258
 259         /* get the actual root for this mount */
 260         error = server->nfs_client->rpc_ops->getattr(server, mntfh, &fattr);
 261         if (error < 0) {
 262                 dprintk("nfs_get_root: getattr error = %d\n", -error);
 263                 return ERR_PTR(error);
 264         }
 265
 266         inode = nfs_fhget(sb, mntfh, &fattr);
 267         if (IS_ERR(inode)) {
 268                 dprintk("nfs_get_root: get root inode failed\n");
 269                 return ERR_CAST(inode);
 270         }
 271
 272         error = nfs_superblock_set_dummy_root(sb, inode);
 273         if (error != 0)
 274                 return ERR_PTR(error);
 275
 276         /* root dentries normally start off anonymous and get spliced in later
 277          * if the dentry tree reaches them; however if the dentry already
 278          * exists, we'll pick it up at this point and use it as the root
 279          */
 280         mntroot = d_alloc_anon(inode);
 281         if (!mntroot) {
 282                 iput(inode);
 283                 dprintk("nfs_get_root: get root dentry failed\n");
 284                 return ERR_PTR(-ENOMEM);
 285         }
 286
 287         security_d_instantiate(mntroot, inode);
 288
 289         if (!mntroot->d_op)
 290                 mntroot->d_op = server->nfs_client->rpc_ops->dentry_ops;
 291
 292         dprintk("<-- nfs4_get_root()\n");
 293         return mntroot;
 294 }
 295
 296 #endif /* CONFIG_NFS_V4 */