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
  23 static void nfs_expire_automounts(struct work_struct *work);
  24
  25 static LIST_HEAD(nfs_automount_list);
  26 static DECLARE_DELAYED_WORK(nfs_automount_task, nfs_expire_automounts);
  27 int nfs_mountpoint_expiry_timeout = 500 * HZ;
  28
  29 static 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  */
  48 char *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
  55 rename_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;
 112 Elong_unlock:
 113         spin_unlock(&dentry->d_lock);
 114         rcu_read_unlock();
 115         if (read_seqretry(&rename_lock, seq))
 116                 goto rename_retry;
 117 Elong:
 118         return ERR_PTR(-ENAMETOOLONG);
 119 }
 120
 121 #ifdef CONFIG_NFS_V4
 122 static rpc_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
 151 static 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
 173 out:
 174         return ret;
 175 }
 176
 177 static 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);
 198 out_shutdown:
 199         rpc_shutdown_client(clone);
 200 out:
 201         return err;
 202 }
 203 #else /* CONFIG_NFS_V4 */
 204 static 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  */
 226 struct 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
 275 out:
 276         nfs_free_fattr(fattr);
 277         nfs_free_fhandle(fh);
 278 out_nofree:
 279         dprintk("<-- nfs_follow_mountpoint() = %p\n", mnt);
 280         return mnt;
 281 }
 282
 283 const struct inode_operations nfs_mountpoint_inode_operations = {
 284         .getattr        = nfs_getattr,
 285 };
 286
 287 const struct inode_operations nfs_referral_inode_operations = {
 288 };
 289
 290 static 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
 299 void 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  */
 308 static 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  */
 336 static 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);
 364 free_page:
 365         free_page((unsigned long)page);
 366 out:
 367         dprintk("%s: done\n", __func__);
 368
 369         dprintk("<-- nfs_do_submount() = %p\n", mnt);
 370         return mnt;
 371 }