fs/nfs/namespace.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * linux/fs/nfs/namespace.c
   4  *
   5  * Copyright (C) 2005 Trond Myklebust <Trond.Myklebust@netapp.com>
   6  * - Modified by David Howells <dhowells@redhat.com>
   7  *
   8  * NFS namespace
   9  */
  10
  11 #include <linux/module.h>
  12 #include <linux/dcache.h>
  13 #include <linux/gfp.h>
  14 #include <linux/mount.h>
  15 #include <linux/namei.h>
  16 #include <linux/nfs_fs.h>
  17 #include <linux/string.h>
  18 #include <linux/sunrpc/clnt.h>
  19 #include <linux/vfs.h>
  20 #include <linux/sunrpc/gss_api.h>
  21 #include "internal.h"
  22 #include "nfs.h"
  23
  24 #define NFSDBG_FACILITY         NFSDBG_VFS
  25
  26 static void nfs_expire_automounts(struct work_struct *work);
  27
  28 static LIST_HEAD(nfs_automount_list);
  29 static DECLARE_DELAYED_WORK(nfs_automount_task, nfs_expire_automounts);
  30 int nfs_mountpoint_expiry_timeout = 500 * HZ;
  31
  32 /*
  33  * nfs_path - reconstruct the path given an arbitrary dentry
  34  * @base - used to return pointer to the end of devname part of path
  35  * @dentry_in - pointer to dentry
  36  * @buffer - result buffer
  37  * @buflen_in - length of buffer
  38  * @flags - options (see below)
  39  *
  40  * Helper function for constructing the server pathname
  41  * by arbitrary hashed dentry.
  42  *
  43  * This is mainly for use in figuring out the path on the
  44  * server side when automounting on top of an existing partition
  45  * and in generating /proc/mounts and friends.
  46  *
  47  * Supported flags:
  48  * NFS_PATH_CANONICAL: ensure there is exactly one slash after
  49  *                     the original device (export) name
  50  *                     (if unset, the original name is returned verbatim)
  51  */
  52 char *nfs_path(char **p, struct dentry *dentry_in, char *buffer,
  53                ssize_t buflen_in, unsigned flags)
  54 {
  55         char *end;
  56         int namelen;
  57         unsigned seq;
  58         const char *base;
  59         struct dentry *dentry;
  60         ssize_t buflen;
  61
  62 rename_retry:
  63         buflen = buflen_in;
  64         dentry = dentry_in;
  65         end = buffer+buflen;
  66         *--end = '\0';
  67         buflen--;
  68
  69         seq = read_seqbegin(&rename_lock);
  70         rcu_read_lock();
  71         while (1) {
  72                 spin_lock(&dentry->d_lock);
  73                 if (IS_ROOT(dentry))
  74                         break;
  75                 namelen = dentry->d_name.len;
  76                 buflen -= namelen + 1;
  77                 if (buflen < 0)
  78                         goto Elong_unlock;
  79                 end -= namelen;
  80                 memcpy(end, dentry->d_name.name, namelen);
  81                 *--end = '/';
  82                 spin_unlock(&dentry->d_lock);
  83                 dentry = dentry->d_parent;
  84         }
  85         if (read_seqretry(&rename_lock, seq)) {
  86                 spin_unlock(&dentry->d_lock);
  87                 rcu_read_unlock();
  88                 goto rename_retry;
  89         }
  90         if ((flags & NFS_PATH_CANONICAL) && *end != '/') {
  91                 if (--buflen < 0) {
  92                         spin_unlock(&dentry->d_lock);
  93                         rcu_read_unlock();
  94                         goto Elong;
  95                 }
  96                 *--end = '/';
  97         }
  98         *p = end;
  99         base = dentry->d_fsdata;
 100         if (!base) {
 101                 spin_unlock(&dentry->d_lock);
 102                 rcu_read_unlock();
 103                 WARN_ON(1);
 104                 return end;
 105         }
 106         namelen = strlen(base);
 107         if (*end == '/') {
 108                 /* Strip off excess slashes in base string */
 109                 while (namelen > 0 && base[namelen - 1] == '/')
 110                         namelen--;
 111         }
 112         buflen -= namelen;
 113         if (buflen < 0) {
 114                 spin_unlock(&dentry->d_lock);
 115                 rcu_read_unlock();
 116                 goto Elong;
 117         }
 118         end -= namelen;
 119         memcpy(end, base, namelen);
 120         spin_unlock(&dentry->d_lock);
 121         rcu_read_unlock();
 122         return end;
 123 Elong_unlock:
 124         spin_unlock(&dentry->d_lock);
 125         rcu_read_unlock();
 126         if (read_seqretry(&rename_lock, seq))
 127                 goto rename_retry;
 128 Elong:
 129         return ERR_PTR(-ENAMETOOLONG);
 130 }
 131 EXPORT_SYMBOL_GPL(nfs_path);
 132
 133 /*
 134  * nfs_d_automount - Handle crossing a mountpoint on the server
 135  * @path - The mountpoint
 136  *
 137  * When we encounter a mountpoint on the server, we want to set up
 138  * a mountpoint on the client too, to prevent inode numbers from
 139  * colliding, and to allow "df" to work properly.
 140  * On NFSv4, we also want to allow for the fact that different
 141  * filesystems may be migrated to different servers in a failover
 142  * situation, and that different filesystems may want to use
 143  * different security flavours.
 144  */
 145 struct vfsmount *nfs_d_automount(struct path *path)
 146 {
 147         struct nfs_fs_context *ctx;
 148         struct fs_context *fc;
 149         struct vfsmount *mnt = ERR_PTR(-ENOMEM);
 150         struct nfs_server *server = NFS_SB(path->dentry->d_sb);
 151         struct nfs_client *client = server->nfs_client;
 152         int timeout = READ_ONCE(nfs_mountpoint_expiry_timeout);
 153         int ret;
 154
 155         if (IS_ROOT(path->dentry))
 156                 return ERR_PTR(-ESTALE);
 157
 158         /* Open a new filesystem context, transferring parameters from the
 159          * parent superblock, including the network namespace.
 160          */
 161         fc = fs_context_for_submount(path->mnt->mnt_sb->s_type, path->dentry);
 162         if (IS_ERR(fc))
 163                 return ERR_CAST(fc);
 164
 165         ctx = nfs_fc2context(fc);
 166         ctx->clone_data.dentry  = path->dentry;
 167         ctx->clone_data.sb      = path->dentry->d_sb;
 168         ctx->clone_data.fattr   = nfs_alloc_fattr();
 169         if (!ctx->clone_data.fattr)
 170                 goto out_fc;
 171
 172         if (fc->net_ns != client->cl_net) {
 173                 put_net(fc->net_ns);
 174                 fc->net_ns = get_net(client->cl_net);
 175         }
 176
 177         /* for submounts we want the same server; referrals will reassign */
 178         memcpy(&ctx->nfs_server._address, &client->cl_addr, client->cl_addrlen);
 179         ctx->nfs_server.addrlen = client->cl_addrlen;
 180         ctx->nfs_server.port    = server->port;
 181
 182         ctx->version            = client->rpc_ops->version;
 183         ctx->minorversion       = client->cl_minorversion;
 184         ctx->nfs_mod            = client->cl_nfs_mod;
 185         get_nfs_version(ctx->nfs_mod);
 186
 187         ret = client->rpc_ops->submount(fc, server);
 188         if (ret < 0) {
 189                 mnt = ERR_PTR(ret);
 190                 goto out_fc;
 191         }
 192
 193         up_write(&fc->root->d_sb->s_umount);
 194         mnt = vfs_create_mount(fc);
 195         if (IS_ERR(mnt))
 196                 goto out_fc;
 197
 198         mntget(mnt); /* prevent immediate expiration */
 199         if (timeout <= 0)
 200                 goto out_fc;
 201
 202         mnt_set_expiry(mnt, &nfs_automount_list);
 203         schedule_delayed_work(&nfs_automount_task, timeout);
 204
 205 out_fc:
 206         put_fs_context(fc);
 207         return mnt;
 208 }
 209
 210 static int
 211 nfs_namespace_getattr(struct mnt_idmap *idmap,
 212                       const struct path *path, struct kstat *stat,
 213                       u32 request_mask, unsigned int query_flags)
 214 {
 215         if (NFS_FH(d_inode(path->dentry))->size != 0)
 216                 return nfs_getattr(idmap, path, stat, request_mask,
 217                                    query_flags);
 218         generic_fillattr(&nop_mnt_idmap, request_mask, d_inode(path->dentry),
 219                          stat);
 220         return 0;
 221 }
 222
 223 static int
 224 nfs_namespace_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
 225                       struct iattr *attr)
 226 {
 227         if (NFS_FH(d_inode(dentry))->size != 0)
 228                 return nfs_setattr(idmap, dentry, attr);
 229         return -EACCES;
 230 }
 231
 232 const struct inode_operations nfs_mountpoint_inode_operations = {
 233         .getattr        = nfs_getattr,
 234         .setattr        = nfs_setattr,
 235 };
 236
 237 const struct inode_operations nfs_referral_inode_operations = {
 238         .getattr        = nfs_namespace_getattr,
 239         .setattr        = nfs_namespace_setattr,
 240 };
 241
 242 static void nfs_expire_automounts(struct work_struct *work)
 243 {
 244         struct list_head *list = &nfs_automount_list;
 245         int timeout = READ_ONCE(nfs_mountpoint_expiry_timeout);
 246
 247         mark_mounts_for_expiry(list);
 248         if (!list_empty(list) && timeout > 0)
 249                 schedule_delayed_work(&nfs_automount_task, timeout);
 250 }
 251
 252 void nfs_release_automount_timer(void)
 253 {
 254         if (list_empty(&nfs_automount_list))
 255                 cancel_delayed_work(&nfs_automount_task);
 256 }
 257
 258 /**
 259  * nfs_do_submount - set up mountpoint when crossing a filesystem boundary
 260  * @fc: pointer to struct nfs_fs_context
 261  *
 262  */
 263 int nfs_do_submount(struct fs_context *fc)
 264 {
 265         struct nfs_fs_context *ctx = nfs_fc2context(fc);
 266         struct dentry *dentry = ctx->clone_data.dentry;
 267         struct nfs_server *server;
 268         char *buffer, *p;
 269         int ret;
 270
 271         /* create a new volume representation */
 272         server = ctx->nfs_mod->rpc_ops->clone_server(NFS_SB(ctx->clone_data.sb),
 273                                                      ctx->mntfh,
 274                                                      ctx->clone_data.fattr,
 275                                                      ctx->selected_flavor);
 276
 277         if (IS_ERR(server))
 278                 return PTR_ERR(server);
 279
 280         ctx->server = server;
 281
 282         buffer = kmalloc(4096, GFP_USER);
 283         if (!buffer)
 284                 return -ENOMEM;
 285
 286         ctx->internal           = true;
 287         ctx->clone_data.inherited_bsize = ctx->clone_data.sb->s_blocksize_bits;
 288
 289         p = nfs_devname(dentry, buffer, 4096);
 290         if (IS_ERR(p)) {
 291                 nfs_errorf(fc, "NFS: Couldn't determine submount pathname");
 292                 ret = PTR_ERR(p);
 293         } else {
 294                 ret = vfs_parse_fs_string(fc, "source", p, buffer + 4096 - p);
 295                 if (!ret)
 296                         ret = vfs_get_tree(fc);
 297         }
 298         kfree(buffer);
 299         return ret;
 300 }
 301 EXPORT_SYMBOL_GPL(nfs_do_submount);
 302
 303 int nfs_submount(struct fs_context *fc, struct nfs_server *server)
 304 {
 305         struct nfs_fs_context *ctx = nfs_fc2context(fc);
 306         struct dentry *dentry = ctx->clone_data.dentry;
 307         struct dentry *parent = dget_parent(dentry);
 308         int err;
 309
 310         /* Look it up again to get its attributes */
 311         err = server->nfs_client->rpc_ops->lookup(d_inode(parent), dentry,
 312                                                   ctx->mntfh, ctx->clone_data.fattr);
 313         dput(parent);
 314         if (err != 0)
 315                 return err;
 316
 317         ctx->selected_flavor = server->client->cl_auth->au_flavor;
 318         return nfs_do_submount(fc);
 319 }
 320 EXPORT_SYMBOL_GPL(nfs_submount);
 321
 322 static int param_set_nfs_timeout(const char *val, const struct kernel_param *kp)
 323 {
 324         long num;
 325         int ret;
 326
 327         if (!val)
 328                 return -EINVAL;
 329         ret = kstrtol(val, 0, &num);
 330         if (ret)
 331                 return -EINVAL;
 332         if (num > 0) {
 333                 if (num >= INT_MAX / HZ)
 334                         num = INT_MAX;
 335                 else
 336                         num *= HZ;
 337                 *((int *)kp->arg) = num;
 338                 if (!list_empty(&nfs_automount_list))
 339                         mod_delayed_work(system_wq, &nfs_automount_task, num);
 340         } else {
 341                 *((int *)kp->arg) = -1*HZ;
 342                 cancel_delayed_work(&nfs_automount_task);
 343         }
 344         return 0;
 345 }
 346
 347 static int param_get_nfs_timeout(char *buffer, const struct kernel_param *kp)
 348 {
 349         long num = *((int *)kp->arg);
 350
 351         if (num > 0) {
 352                 if (num >= INT_MAX - (HZ - 1))
 353                         num = INT_MAX / HZ;
 354                 else
 355                         num = (num + (HZ - 1)) / HZ;
 356         } else
 357                 num = -1;
 358         return sysfs_emit(buffer, "%li\n", num);
 359 }
 360
 361 static const struct kernel_param_ops param_ops_nfs_timeout = {
 362         .set = param_set_nfs_timeout,
 363         .get = param_get_nfs_timeout,
 364 };
 365 #define param_check_nfs_timeout(name, p) __param_check(name, p, int)
 366
 367 module_param(nfs_mountpoint_expiry_timeout, nfs_timeout, 0644);
 368 MODULE_PARM_DESC(nfs_mountpoint_expiry_timeout,
 369                 "Set the NFS automounted mountpoint timeout value (seconds)."
 370                 "Values <= 0 turn expiration off.");