LXR linux/fs/nfs/namespace.c

   1/*
   2 * linux/fs/nfs/namespace.c
   3 *
   4 * Copyright (C) 2005 Trond Myklebust <Trond.Myklebust@netapp.com>
   5 * - Modified by David Howells <dhowells@redhat.com>
   6 *
   7 * NFS namespace
   8 */
   9
  10#include <linux/dcache.h>
  11#include <linux/gfp.h>
  12#include <linux/mount.h>
  13#include <linux/namei.h>
  14#include <linux/nfs_fs.h>
  15#include <linux/string.h>
  16#include <linux/sunrpc/clnt.h>
  17#include <linux/vfs.h>
  18#include <linux/sunrpc/gss_api.h>
  19#include "internal.h"
  20
  21#define NFSDBG_FACILITY         NFSDBG_VFS
  22
  23static void nfs_expire_automounts(struct work_struct *work);
  24
  25static LIST_HEAD(nfs_automount_list);
  26static DECLARE_DELAYED_WORK(nfs_automount_task, nfs_expire_automounts);
  27int nfs_mountpoint_expiry_timeout = 500 * HZ;
  28
  29static struct vfsmount *nfs_do_submount(struct dentry *dentry,
  30                                        struct nfs_fh *fh,
  31                                        struct nfs_fattr *fattr,
  32                                        rpc_authflavor_t authflavor);
  33
  34/*
  35 * nfs_path - reconstruct the path given an arbitrary dentry
  36 * @base - used to return pointer to the end of devname part of path
  37 * @dentry - pointer to dentry
  38 * @buffer - result buffer
  39 * @buflen - length of buffer
  40 *
  41 * Helper function for constructing the server pathname
  42 * by arbitrary hashed dentry.
  43 *
  44 * This is mainly for use in figuring out the path on the
  45 * server side when automounting on top of an existing partition
  46 * and in generating /proc/mounts and friends.
  47 */
  48char *nfs_path(char **p, struct dentry *dentry, char *buffer, ssize_t buflen)
  49{
  50        char *end;
  51        int namelen;
  52        unsigned seq;
  53        const char *base;
  54
  55rename_retry:
  56        end = buffer+buflen;
  57        *--end = '\0';
  58        buflen--;
  59
  60        seq = read_seqbegin(&rename_lock);
  61        rcu_read_lock();
  62        while (1) {
  63                spin_lock(&dentry->d_lock);
  64                if (IS_ROOT(dentry))
  65                        break;
  66                namelen = dentry->d_name.len;
  67                buflen -= namelen + 1;
  68                if (buflen < 0)
  69                        goto Elong_unlock;
  70                end -= namelen;
  71                memcpy(end, dentry->d_name.name, namelen);
  72                *--end = '/';
  73                spin_unlock(&dentry->d_lock);
  74                dentry = dentry->d_parent;
  75        }
  76        if (read_seqretry(&rename_lock, seq)) {
  77                spin_unlock(&dentry->d_lock);
  78                rcu_read_unlock();
  79                goto rename_retry;
  80        }
  81        if (*end != '/') {
  82                if (--buflen < 0) {
  83                        spin_unlock(&dentry->d_lock);
  84                        rcu_read_unlock();
  85                        goto Elong;
  86                }
  87                *--end = '/';
  88        }
  89        *p = end;
  90        base = dentry->d_fsdata;
  91        if (!base) {
  92                spin_unlock(&dentry->d_lock);
  93                rcu_read_unlock();
  94                WARN_ON(1);
  95                return end;
  96        }
  97        namelen = strlen(base);
  98        /* Strip off excess slashes in base string */
  99        while (namelen > 0 && base[namelen - 1] == '/')
 100                namelen--;
 101        buflen -= namelen;
 102        if (buflen < 0) {
 103                spin_unlock(&dentry->d_lock);
 104                rcu_read_unlock();
 105                goto Elong;
 106        }
 107        end -= namelen;
 108        memcpy(end, base, namelen);
 109        spin_unlock(&dentry->d_lock);
 110        rcu_read_unlock();
 111        return end;
 112Elong_unlock:
 113        spin_unlock(&dentry->d_lock);
 114        rcu_read_unlock();
 115        if (read_seqretry(&rename_lock, seq))
 116                goto rename_retry;
 117Elong:
 118        return ERR_PTR(-ENAMETOOLONG);
 119}
 120
 121#ifdef CONFIG_NFS_V4
 122rpc_authflavor_t nfs_find_best_sec(struct nfs4_secinfo_flavors *flavors)
 123{
 124        struct gss_api_mech *mech;
 125        struct xdr_netobj oid;
 126        int i;
 127        rpc_authflavor_t pseudoflavor = RPC_AUTH_UNIX;
 128
 129        for (i = 0; i < flavors->num_flavors; i++) {
 130                struct nfs4_secinfo_flavor *flavor;
 131                flavor = &flavors->flavors[i];
 132
 133                if (flavor->flavor == RPC_AUTH_NULL || flavor->flavor == RPC_AUTH_UNIX) {
 134                        pseudoflavor = flavor->flavor;
 135                        break;
 136                } else if (flavor->flavor == RPC_AUTH_GSS) {
 137                        oid.len  = flavor->gss.sec_oid4.len;
 138                        oid.data = flavor->gss.sec_oid4.data;
 139                        mech = gss_mech_get_by_OID(&oid);
 140                        if (!mech)
 141                                continue;
 142                        pseudoflavor = gss_svc_to_pseudoflavor(mech, flavor->gss.service);
 143                        gss_mech_put(mech);
 144                        break;
 145                }
 146        }
 147
 148        return pseudoflavor;
 149}
 150
 151static int nfs_negotiate_security(const struct dentry *parent,
 152                                  const struct dentry *dentry,
 153                                  rpc_authflavor_t *flavor)
 154{
 155        struct page *page;
 156        struct nfs4_secinfo_flavors *flavors;
 157        int (*secinfo)(struct inode *, const struct qstr *, struct nfs4_secinfo_flavors *);
 158        int ret = -EPERM;
 159
 160        secinfo = NFS_PROTO(parent->d_inode)->secinfo;
 161        if (secinfo != NULL) {
 162                page = alloc_page(GFP_KERNEL);
 163                if (!page) {
 164                        ret = -ENOMEM;
 165                        goto out;
 166                }
 167                flavors = page_address(page);
 168                ret = secinfo(parent->d_inode, &dentry->d_name, flavors);
 169                *flavor = nfs_find_best_sec(flavors);
 170                put_page(page);
 171        }
 172
 173out:
 174        return ret;
 175}
 176
 177static int nfs_lookup_with_sec(struct nfs_server *server, struct dentry *parent,
 178                               struct dentry *dentry, struct path *path,
 179                               struct nfs_fh *fh, struct nfs_fattr *fattr,
 180                               rpc_authflavor_t *flavor)
 181{
 182        struct rpc_clnt *clone;
 183        struct rpc_auth *auth;
 184        int err;
 185
 186        err = nfs_negotiate_security(parent, path->dentry, flavor);
 187        if (err < 0)
 188                goto out;
 189        clone  = rpc_clone_client(server->client);
 190        auth   = rpcauth_create(*flavor, clone);
 191        if (!auth) {
 192                err = -EIO;
 193                goto out_shutdown;
 194        }
 195        err = server->nfs_client->rpc_ops->lookup(clone, parent->d_inode,
 196                                                  &path->dentry->d_name,
 197                                                  fh, fattr);
 198out_shutdown:
 199        rpc_shutdown_client(clone);
 200out:
 201        return err;
 202}
 203#else /* CONFIG_NFS_V4 */
 204static inline int nfs_lookup_with_sec(struct nfs_server *server,
 205                                      struct dentry *parent, struct dentry *dentry,
 206                                      struct path *path, struct nfs_fh *fh,
 207                                      struct nfs_fattr *fattr,
 208                                      rpc_authflavor_t *flavor)
 209{
 210        return -EPERM;
 211}
 212#endif /* CONFIG_NFS_V4 */
 213
 214/*
 215 * nfs_d_automount - Handle crossing a mountpoint on the server
 216 * @path - The mountpoint
 217 *
 218 * When we encounter a mountpoint on the server, we want to set up
 219 * a mountpoint on the client too, to prevent inode numbers from
 220 * colliding, and to allow "df" to work properly.
 221 * On NFSv4, we also want to allow for the fact that different
 222 * filesystems may be migrated to different servers in a failover
 223 * situation, and that different filesystems may want to use
 224 * different security flavours.
 225 */
 226struct vfsmount *nfs_d_automount(struct path *path)
 227{
 228        struct vfsmount *mnt;
 229        struct nfs_server *server = NFS_SERVER(path->dentry->d_inode);
 230        struct dentry *parent;
 231        struct nfs_fh *fh = NULL;
 232        struct nfs_fattr *fattr = NULL;
 233        int err;
 234        rpc_authflavor_t flavor = RPC_AUTH_UNIX;
 235
 236        dprintk("--> nfs_d_automount()\n");
 237
 238        mnt = ERR_PTR(-ESTALE);
 239        if (IS_ROOT(path->dentry))
 240                goto out_nofree;
 241
 242        mnt = ERR_PTR(-ENOMEM);
 243        fh = nfs_alloc_fhandle();
 244        fattr = nfs_alloc_fattr();
 245        if (fh == NULL || fattr == NULL)
 246                goto out;
 247
 248        dprintk("%s: enter\n", __func__);
 249
 250        /* Look it up again to get its attributes */
 251        parent = dget_parent(path->dentry);
 252        err = server->nfs_client->rpc_ops->lookup(server->client, parent->d_inode,
 253                                                  &path->dentry->d_name,
 254                                                  fh, fattr);
 255        if (err == -EPERM && NFS_PROTO(parent->d_inode)->secinfo != NULL)
 256                err = nfs_lookup_with_sec(server, parent, path->dentry, path, fh, fattr, &flavor);
 257        dput(parent);
 258        if (err != 0) {
 259                mnt = ERR_PTR(err);
 260                goto out;
 261        }
 262
 263        if (fattr->valid & NFS_ATTR_FATTR_V4_REFERRAL)
 264                mnt = nfs_do_refmount(path->dentry);
 265        else
 266                mnt = nfs_do_submount(path->dentry, fh, fattr, flavor);
 267        if (IS_ERR(mnt))
 268                goto out;
 269
 270        dprintk("%s: done, success\n", __func__);
 271        mntget(mnt); /* prevent immediate expiration */
 272        mnt_set_expiry(mnt, &nfs_automount_list);
 273        schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout);
 274
 275out:
 276        nfs_free_fattr(fattr);
 277        nfs_free_fhandle(fh);
 278out_nofree:
 279        dprintk("<-- nfs_follow_mountpoint() = %p\n", mnt);
 280        return mnt;
 281}
 282
 283const struct inode_operations nfs_mountpoint_inode_operations = {
 284        .getattr        = nfs_getattr,
 285};
 286
 287const struct inode_operations nfs_referral_inode_operations = {
 288};
 289
 290static void nfs_expire_automounts(struct work_struct *work)
 291{
 292        struct list_head *list = &nfs_automount_list;
 293
 294        mark_mounts_for_expiry(list);
 295        if (!list_empty(list))
 296                schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout);
 297}
 298
 299void nfs_release_automount_timer(void)
 300{
 301        if (list_empty(&nfs_automount_list))
 302                cancel_delayed_work(&nfs_automount_task);
 303}
 304
 305/*
 306 * Clone a mountpoint of the appropriate type
 307 */
 308static struct vfsmount *nfs_do_clone_mount(struct nfs_server *server,
 309                                           const char *devname,
 310                                           struct nfs_clone_mount *mountdata)
 311{
 312#ifdef CONFIG_NFS_V4
 313        struct vfsmount *mnt = ERR_PTR(-EINVAL);
 314        switch (server->nfs_client->rpc_ops->version) {
 315                case 2:
 316                case 3:
 317                        mnt = vfs_kern_mount(&nfs_xdev_fs_type, 0, devname, mountdata);
 318                        break;
 319                case 4:
 320                        mnt = vfs_kern_mount(&nfs4_xdev_fs_type, 0, devname, mountdata);
 321        }
 322        return mnt;
 323#else
 324        return vfs_kern_mount(&nfs_xdev_fs_type, 0, devname, mountdata);
 325#endif
 326}
 327
 328/**
 329 * nfs_do_submount - set up mountpoint when crossing a filesystem boundary
 330 * @dentry - parent directory
 331 * @fh - filehandle for new root dentry
 332 * @fattr - attributes for new root inode
 333 * @authflavor - security flavor to use when performing the mount
 334 *
 335 */
 336static struct vfsmount *nfs_do_submount(struct dentry *dentry,
 337                                        struct nfs_fh *fh,
 338                                        struct nfs_fattr *fattr,
 339                                        rpc_authflavor_t authflavor)
 340{
 341        struct nfs_clone_mount mountdata = {
 342                .sb = dentry->d_sb,
 343                .dentry = dentry,
 344                .fh = fh,
 345                .fattr = fattr,
 346                .authflavor = authflavor,
 347        };
 348        struct vfsmount *mnt = ERR_PTR(-ENOMEM);
 349        char *page = (char *) __get_free_page(GFP_USER);
 350        char *devname;
 351
 352        dprintk("--> nfs_do_submount()\n");
 353
 354        dprintk("%s: submounting on %s/%s\n", __func__,
 355                        dentry->d_parent->d_name.name,
 356                        dentry->d_name.name);
 357        if (page == NULL)
 358                goto out;
 359        devname = nfs_devname(dentry, page, PAGE_SIZE);
 360        mnt = (struct vfsmount *)devname;
 361        if (IS_ERR(devname))
 362                goto free_page;
 363        mnt = nfs_do_clone_mount(NFS_SB(dentry->d_sb), devname, &mountdata);
 364free_page:
 365        free_page((unsigned long)page);
 366out:
 367        dprintk("%s: done\n", __func__);
 368
 369        dprintk("<-- nfs_do_submount() = %p\n", mnt);
 370        return mnt;
 371}
 372