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 - pointer to dentry
  36  * @buffer - result buffer
  37  * @buflen - 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, char *buffer, ssize_t buflen,
  53                unsigned flags)
  54 {
  55         char *end;
  56         int namelen;
  57         unsigned seq;
  58         const char *base;
  59
  60 rename_retry:
  61         end = buffer+buflen;
  62         *--end = '\0';
  63         buflen--;
  64
  65         seq = read_seqbegin(&rename_lock);
  66         rcu_read_lock();
  67         while (1) {
  68                 spin_lock(&dentry->d_lock);
  69                 if (IS_ROOT(dentry))
  70                         break;
  71                 namelen = dentry->d_name.len;
  72                 buflen -= namelen + 1;
  73                 if (buflen < 0)
  74                         goto Elong_unlock;
  75                 end -= namelen;
  76                 memcpy(end, dentry->d_name.name, namelen);
  77                 *--end = '/';
  78                 spin_unlock(&dentry->d_lock);
  79                 dentry = dentry->d_parent;
  80         }
  81         if (read_seqretry(&rename_lock, seq)) {
  82                 spin_unlock(&dentry->d_lock);
  83                 rcu_read_unlock();
  84                 goto rename_retry;
  85         }
  86         if ((flags & NFS_PATH_CANONICAL) && *end != '/') {
  87                 if (--buflen < 0) {
  88                         spin_unlock(&dentry->d_lock);
  89                         rcu_read_unlock();
  90                         goto Elong;
  91                 }
  92                 *--end = '/';
  93         }
  94         *p = end;
  95         base = dentry->d_fsdata;
  96         if (!base) {
  97                 spin_unlock(&dentry->d_lock);
  98                 rcu_read_unlock();
  99                 WARN_ON(1);
 100                 return end;
 101         }
 102         namelen = strlen(base);
 103         if (*end == '/') {
 104                 /* Strip off excess slashes in base string */
 105                 while (namelen > 0 && base[namelen - 1] == '/')
 106                         namelen--;
 107         }
 108         buflen -= namelen;
 109         if (buflen < 0) {
 110                 spin_unlock(&dentry->d_lock);
 111                 rcu_read_unlock();
 112                 goto Elong;
 113         }
 114         end -= namelen;
 115         memcpy(end, base, namelen);
 116         spin_unlock(&dentry->d_lock);
 117         rcu_read_unlock();
 118         return end;
 119 Elong_unlock:
 120         spin_unlock(&dentry->d_lock);
 121         rcu_read_unlock();
 122         if (read_seqretry(&rename_lock, seq))
 123                 goto rename_retry;
 124 Elong:
 125         return ERR_PTR(-ENAMETOOLONG);
 126 }
 127 EXPORT_SYMBOL_GPL(nfs_path);
 128
 129 /*
 130  * nfs_d_automount - Handle crossing a mountpoint on the server
 131  * @path - The mountpoint
 132  *
 133  * When we encounter a mountpoint on the server, we want to set up
 134  * a mountpoint on the client too, to prevent inode numbers from
 135  * colliding, and to allow "df" to work properly.
 136  * On NFSv4, we also want to allow for the fact that different
 137  * filesystems may be migrated to different servers in a failover
 138  * situation, and that different filesystems may want to use
 139  * different security flavours.
 140  */
 141 struct vfsmount *nfs_d_automount(struct path *path)
 142 {
 143         struct nfs_fs_context *ctx;
 144         struct fs_context *fc;
 145         struct vfsmount *mnt = ERR_PTR(-ENOMEM);
 146         struct nfs_server *server = NFS_SERVER(d_inode(path->dentry));
 147         struct nfs_client *client = server->nfs_client;
 148         int timeout = READ_ONCE(nfs_mountpoint_expiry_timeout);
 149         int ret;
 150
 151         if (IS_ROOT(path->dentry))
 152                 return ERR_PTR(-ESTALE);
 153
 154         /* Open a new filesystem context, transferring parameters from the
 155          * parent superblock, including the network namespace.
 156          */
 157         fc = fs_context_for_submount(path->mnt->mnt_sb->s_type, path->dentry);
 158         if (IS_ERR(fc))
 159                 return ERR_CAST(fc);
 160
 161         ctx = nfs_fc2context(fc);
 162         ctx->clone_data.dentry  = path->dentry;
 163         ctx->clone_data.sb      = path->dentry->d_sb;
 164         ctx->clone_data.fattr   = nfs_alloc_fattr();
 165         if (!ctx->clone_data.fattr)
 166                 goto out_fc;
 167
 168         if (fc->net_ns != client->cl_net) {
 169                 put_net(fc->net_ns);
 170                 fc->net_ns = get_net(client->cl_net);
 171         }
 172
 173         /* for submounts we want the same server; referrals will reassign */
 174         memcpy(&ctx->nfs_server.address, &client->cl_addr, client->cl_addrlen);
 175         ctx->nfs_server.addrlen = client->cl_addrlen;
 176         ctx->nfs_server.port    = server->port;
 177
 178         ctx->version            = client->rpc_ops->version;
 179         ctx->minorversion       = client->cl_minorversion;
 180         ctx->nfs_mod            = client->cl_nfs_mod;
 181         __module_get(ctx->nfs_mod->owner);
 182
 183         ret = client->rpc_ops->submount(fc, server);
 184         if (ret < 0) {
 185                 mnt = ERR_PTR(ret);
 186                 goto out_fc;
 187         }
 188
 189         up_write(&fc->root->d_sb->s_umount);
 190         mnt = vfs_create_mount(fc);
 191         if (IS_ERR(mnt))
 192                 goto out_fc;
 193
 194         mntget(mnt); /* prevent immediate expiration */
 195         if (timeout <= 0)
 196                 goto out_fc;
 197
 198         mnt_set_expiry(mnt, &nfs_automount_list);
 199         schedule_delayed_work(&nfs_automount_task, timeout);
 200
 201 out_fc:
 202         put_fs_context(fc);
 203         return mnt;
 204 }
 205
 206 static int
 207 nfs_namespace_getattr(const struct path *path, struct kstat *stat,
 208                         u32 request_mask, unsigned int query_flags)
 209 {
 210         if (NFS_FH(d_inode(path->dentry))->size != 0)
 211                 return nfs_getattr(path, stat, request_mask, query_flags);
 212         generic_fillattr(d_inode(path->dentry), stat);
 213         return 0;
 214 }
 215
 216 static int
 217 nfs_namespace_setattr(struct dentry *dentry, struct iattr *attr)
 218 {
 219         if (NFS_FH(d_inode(dentry))->size != 0)
 220                 return nfs_setattr(dentry, attr);
 221         return -EACCES;
 222 }
 223
 224 const struct inode_operations nfs_mountpoint_inode_operations = {
 225         .getattr        = nfs_getattr,
 226         .setattr        = nfs_setattr,
 227 };
 228
 229 const struct inode_operations nfs_referral_inode_operations = {
 230         .getattr        = nfs_namespace_getattr,
 231         .setattr        = nfs_namespace_setattr,
 232 };
 233
 234 static void nfs_expire_automounts(struct work_struct *work)
 235 {
 236         struct list_head *list = &nfs_automount_list;
 237         int timeout = READ_ONCE(nfs_mountpoint_expiry_timeout);
 238
 239         mark_mounts_for_expiry(list);
 240         if (!list_empty(list) && timeout > 0)
 241                 schedule_delayed_work(&nfs_automount_task, timeout);
 242 }
 243
 244 void nfs_release_automount_timer(void)
 245 {
 246         if (list_empty(&nfs_automount_list))
 247                 cancel_delayed_work(&nfs_automount_task);
 248 }
 249
 250 /**
 251  * nfs_do_submount - set up mountpoint when crossing a filesystem boundary
 252  * @fc: pointer to struct nfs_fs_context
 253  *
 254  */
 255 int nfs_do_submount(struct fs_context *fc)
 256 {
 257         struct nfs_fs_context *ctx = nfs_fc2context(fc);
 258         struct dentry *dentry = ctx->clone_data.dentry;
 259         struct nfs_server *server;
 260         char *buffer, *p;
 261         int ret;
 262
 263         /* create a new volume representation */
 264         server = ctx->nfs_mod->rpc_ops->clone_server(NFS_SB(ctx->clone_data.sb),
 265                                                      ctx->mntfh,
 266                                                      ctx->clone_data.fattr,
 267                                                      ctx->selected_flavor);
 268
 269         if (IS_ERR(server))
 270                 return PTR_ERR(server);
 271
 272         ctx->server = server;
 273
 274         buffer = kmalloc(4096, GFP_USER);
 275         if (!buffer)
 276                 return -ENOMEM;
 277
 278         ctx->internal           = true;
 279         ctx->clone_data.inherited_bsize = ctx->clone_data.sb->s_blocksize_bits;
 280
 281         p = nfs_devname(dentry, buffer, 4096);
 282         if (IS_ERR(p)) {
 283                 nfs_errorf(fc, "NFS: Couldn't determine submount pathname");
 284                 ret = PTR_ERR(p);
 285         } else {
 286                 ret = vfs_parse_fs_string(fc, "source", p, buffer + 4096 - p);
 287                 if (!ret)
 288                         ret = vfs_get_tree(fc);
 289         }
 290         kfree(buffer);
 291         return ret;
 292 }
 293 EXPORT_SYMBOL_GPL(nfs_do_submount);
 294
 295 int nfs_submount(struct fs_context *fc, struct nfs_server *server)
 296 {
 297         struct nfs_fs_context *ctx = nfs_fc2context(fc);
 298         struct dentry *dentry = ctx->clone_data.dentry;
 299         struct dentry *parent = dget_parent(dentry);
 300         int err;
 301
 302         /* Look it up again to get its attributes */
 303         err = server->nfs_client->rpc_ops->lookup(d_inode(parent), dentry,
 304                                                   ctx->mntfh, ctx->clone_data.fattr,
 305                                                   NULL);
 306         dput(parent);
 307         if (err != 0)
 308                 return err;
 309
 310         ctx->selected_flavor = server->client->cl_auth->au_flavor;
 311         return nfs_do_submount(fc);
 312 }
 313 EXPORT_SYMBOL_GPL(nfs_submount);
 314
 315 static int param_set_nfs_timeout(const char *val, const struct kernel_param *kp)
 316 {
 317         long num;
 318         int ret;
 319
 320         if (!val)
 321                 return -EINVAL;
 322         ret = kstrtol(val, 0, &num);
 323         if (ret)
 324                 return -EINVAL;
 325         if (num > 0) {
 326                 if (num >= INT_MAX / HZ)
 327                         num = INT_MAX;
 328                 else
 329                         num *= HZ;
 330                 *((int *)kp->arg) = num;
 331                 if (!list_empty(&nfs_automount_list))
 332                         mod_delayed_work(system_wq, &nfs_automount_task, num);
 333         } else {
 334                 *((int *)kp->arg) = -1*HZ;
 335                 cancel_delayed_work(&nfs_automount_task);
 336         }
 337         return 0;
 338 }
 339
 340 static int param_get_nfs_timeout(char *buffer, const struct kernel_param *kp)
 341 {
 342         long num = *((int *)kp->arg);
 343
 344         if (num > 0) {
 345                 if (num >= INT_MAX - (HZ - 1))
 346                         num = INT_MAX / HZ;
 347                 else
 348                         num = (num + (HZ - 1)) / HZ;
 349         } else
 350                 num = -1;
 351         return scnprintf(buffer, PAGE_SIZE, "%li\n", num);
 352 }
 353
 354 static const struct kernel_param_ops param_ops_nfs_timeout = {
 355         .set = param_set_nfs_timeout,
 356         .get = param_get_nfs_timeout,
 357 };
 358 #define param_check_nfs_timeout(name, p) __param_check(name, p, int);
 359
 360 module_param(nfs_mountpoint_expiry_timeout, nfs_timeout, 0644);
 361 MODULE_PARM_DESC(nfs_mountpoint_expiry_timeout,
 362                 "Set the NFS automounted mountpoint timeout value (seconds)."
 363                 "Values <= 0 turn expiration off.");