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, struct inode *inode)
 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 rpc_authflavor_t nfs_negotiate_security(const struct dentry *parent, const struct dentry *dentry)
 152 {
 153         int status = 0;
 154         struct page *page;
 155         struct nfs4_secinfo_flavors *flavors;
 156         int (*secinfo)(struct inode *, const struct qstr *, struct nfs4_secinfo_flavors *);
 157         rpc_authflavor_t flavor = RPC_AUTH_UNIX;
 158
 159         secinfo = NFS_PROTO(parent->d_inode)->secinfo;
 160         if (secinfo != NULL) {
 161                 page = alloc_page(GFP_KERNEL);
 162                 if (!page) {
 163                         status = -ENOMEM;
 164                         goto out;
 165                 }
 166                 flavors = page_address(page);
 167                 status = secinfo(parent->d_inode, &dentry->d_name, flavors);
 168                 flavor = nfs_find_best_sec(flavors, dentry->d_inode);
 169                 put_page(page);
 170         }
 171
 172         return flavor;
 173
 174 out:
 175         status = -ENOMEM;
 176         return status;
 177 }
 178
 179 static rpc_authflavor_t nfs_lookup_with_sec(struct nfs_server *server, struct dentry *parent,
 180                                      struct dentry *dentry, struct path *path,
 181                                      struct nfs_fh *fh, struct nfs_fattr *fattr)
 182 {
 183         rpc_authflavor_t flavor;
 184         struct rpc_clnt *clone;
 185         struct rpc_auth *auth;
 186         int err;
 187
 188         flavor = nfs_negotiate_security(parent, path->dentry);
 189         if (flavor < 0)
 190                 goto out;
 191         clone  = rpc_clone_client(server->client);
 192         auth   = rpcauth_create(flavor, clone);
 193         if (!auth) {
 194                 flavor = -EIO;
 195                 goto out_shutdown;
 196         }
 197         err = server->nfs_client->rpc_ops->lookup(clone, parent->d_inode,
 198                                                   &path->dentry->d_name,
 199                                                   fh, fattr);
 200         if (err < 0)
 201                 flavor = err;
 202 out_shutdown:
 203         rpc_shutdown_client(clone);
 204 out:
 205         return flavor;
 206 }
 207 #else /* CONFIG_NFS_V4 */
 208 static inline rpc_authflavor_t nfs_lookup_with_sec(struct nfs_server *server,
 209                                      struct dentry *parent, struct dentry *dentry,
 210                                      struct path *path, struct nfs_fh *fh,
 211                                      struct nfs_fattr *fattr)
 212 {
 213         return -EPERM;
 214 }
 215 #endif /* CONFIG_NFS_V4 */
 216
 217 /*
 218  * nfs_d_automount - Handle crossing a mountpoint on the server
 219  * @path - The mountpoint
 220  *
 221  * When we encounter a mountpoint on the server, we want to set up
 222  * a mountpoint on the client too, to prevent inode numbers from
 223  * colliding, and to allow "df" to work properly.
 224  * On NFSv4, we also want to allow for the fact that different
 225  * filesystems may be migrated to different servers in a failover
 226  * situation, and that different filesystems may want to use
 227  * different security flavours.
 228  */
 229 struct vfsmount *nfs_d_automount(struct path *path)
 230 {
 231         struct vfsmount *mnt;
 232         struct nfs_server *server = NFS_SERVER(path->dentry->d_inode);
 233         struct dentry *parent;
 234         struct nfs_fh *fh = NULL;
 235         struct nfs_fattr *fattr = NULL;
 236         int err;
 237         rpc_authflavor_t flavor = 1;
 238
 239         dprintk("--> nfs_d_automount()\n");
 240
 241         mnt = ERR_PTR(-ESTALE);
 242         if (IS_ROOT(path->dentry))
 243                 goto out_nofree;
 244
 245         mnt = ERR_PTR(-ENOMEM);
 246         fh = nfs_alloc_fhandle();
 247         fattr = nfs_alloc_fattr();
 248         if (fh == NULL || fattr == NULL)
 249                 goto out;
 250
 251         dprintk("%s: enter\n", __func__);
 252
 253         /* Look it up again to get its attributes */
 254         parent = dget_parent(path->dentry);
 255         err = server->nfs_client->rpc_ops->lookup(server->client, parent->d_inode,
 256                                                   &path->dentry->d_name,
 257                                                   fh, fattr);
 258         if (err == -EPERM) {
 259                 flavor = nfs_lookup_with_sec(server, parent, path->dentry, path, fh, fattr);
 260                 if (flavor < 0)
 261                         err = flavor;
 262                 else
 263                         err = 0;
 264         }
 265         dput(parent);
 266         if (err != 0) {
 267                 mnt = ERR_PTR(err);
 268                 goto out;
 269         }
 270
 271         if (fattr->valid & NFS_ATTR_FATTR_V4_REFERRAL)
 272                 mnt = nfs_do_refmount(path->dentry);
 273         else
 274                 mnt = nfs_do_submount(path->dentry, fh, fattr, flavor);
 275         if (IS_ERR(mnt))
 276                 goto out;
 277
 278         dprintk("%s: done, success\n", __func__);
 279         mntget(mnt); /* prevent immediate expiration */
 280         mnt_set_expiry(mnt, &nfs_automount_list);
 281         schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout);
 282
 283 out:
 284         nfs_free_fattr(fattr);
 285         nfs_free_fhandle(fh);
 286 out_nofree:
 287         dprintk("<-- nfs_follow_mountpoint() = %p\n", mnt);
 288         return mnt;
 289 }
 290
 291 const struct inode_operations nfs_mountpoint_inode_operations = {
 292         .getattr        = nfs_getattr,
 293 };
 294
 295 const struct inode_operations nfs_referral_inode_operations = {
 296 };
 297
 298 static void nfs_expire_automounts(struct work_struct *work)
 299 {
 300         struct list_head *list = &nfs_automount_list;
 301
 302         mark_mounts_for_expiry(list);
 303         if (!list_empty(list))
 304                 schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout);
 305 }
 306
 307 void nfs_release_automount_timer(void)
 308 {
 309         if (list_empty(&nfs_automount_list))
 310                 cancel_delayed_work(&nfs_automount_task);
 311 }
 312
 313 /*
 314  * Clone a mountpoint of the appropriate type
 315  */
 316 static struct vfsmount *nfs_do_clone_mount(struct nfs_server *server,
 317                                            const char *devname,
 318                                            struct nfs_clone_mount *mountdata)
 319 {
 320 #ifdef CONFIG_NFS_V4
 321         struct vfsmount *mnt = ERR_PTR(-EINVAL);
 322         switch (server->nfs_client->rpc_ops->version) {
 323                 case 2:
 324                 case 3:
 325                         mnt = vfs_kern_mount(&nfs_xdev_fs_type, 0, devname, mountdata);
 326                         break;
 327                 case 4:
 328                         mnt = vfs_kern_mount(&nfs4_xdev_fs_type, 0, devname, mountdata);
 329         }
 330         return mnt;
 331 #else
 332         return vfs_kern_mount(&nfs_xdev_fs_type, 0, devname, mountdata);
 333 #endif
 334 }
 335
 336 /**
 337  * nfs_do_submount - set up mountpoint when crossing a filesystem boundary
 338  * @dentry - parent directory
 339  * @fh - filehandle for new root dentry
 340  * @fattr - attributes for new root inode
 341  * @authflavor - security flavor to use when performing the mount
 342  *
 343  */
 344 static struct vfsmount *nfs_do_submount(struct dentry *dentry,
 345                                         struct nfs_fh *fh,
 346                                         struct nfs_fattr *fattr,
 347                                         rpc_authflavor_t authflavor)
 348 {
 349         struct nfs_clone_mount mountdata = {
 350                 .sb = dentry->d_sb,
 351                 .dentry = dentry,
 352                 .fh = fh,
 353                 .fattr = fattr,
 354                 .authflavor = authflavor,
 355         };
 356         struct vfsmount *mnt = ERR_PTR(-ENOMEM);
 357         char *page = (char *) __get_free_page(GFP_USER);
 358         char *devname;
 359
 360         dprintk("--> nfs_do_submount()\n");
 361
 362         dprintk("%s: submounting on %s/%s\n", __func__,
 363                         dentry->d_parent->d_name.name,
 364                         dentry->d_name.name);
 365         if (page == NULL)
 366                 goto out;
 367         devname = nfs_devname(dentry, page, PAGE_SIZE);
 368         mnt = (struct vfsmount *)devname;
 369         if (IS_ERR(devname))
 370                 goto free_page;
 371         mnt = nfs_do_clone_mount(NFS_SB(dentry->d_sb), devname, &mountdata);
 372 free_page:
 373         free_page((unsigned long)page);
 374 out:
 375         dprintk("%s: done\n", __func__);
 376
 377         dprintk("<-- nfs_do_submount() = %p\n", mnt);
 378         return mnt;
 379 }