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 ret;
 149
 150         if (IS_ROOT(path->dentry))
 151                 return ERR_PTR(-ESTALE);
 152
 153         /* Open a new filesystem context, transferring parameters from the
 154          * parent superblock, including the network namespace.
 155          */
 156         fc = fs_context_for_submount(&nfs_fs_type, path->dentry);
 157         if (IS_ERR(fc))
 158                 return ERR_CAST(fc);
 159
 160         ctx = nfs_fc2context(fc);
 161         ctx->clone_data.dentry  = path->dentry;
 162         ctx->clone_data.sb      = path->dentry->d_sb;
 163         ctx->clone_data.fattr   = nfs_alloc_fattr();
 164         if (!ctx->clone_data.fattr)
 165                 goto out_fc;
 166
 167         if (fc->net_ns != client->cl_net) {
 168                 put_net(fc->net_ns);
 169                 fc->net_ns = get_net(client->cl_net);
 170         }
 171
 172         /* for submounts we want the same server; referrals will reassign */
 173         memcpy(&ctx->nfs_server.address, &client->cl_addr, client->cl_addrlen);
 174         ctx->nfs_server.addrlen = client->cl_addrlen;
 175         ctx->nfs_server.port    = server->port;
 176
 177         ctx->version            = client->rpc_ops->version;
 178         ctx->minorversion       = client->cl_minorversion;
 179         ctx->nfs_mod            = client->cl_nfs_mod;
 180         __module_get(ctx->nfs_mod->owner);
 181
 182         ret = client->rpc_ops->submount(fc, server);
 183         if (ret < 0) {
 184                 mnt = ERR_PTR(ret);
 185                 goto out_fc;
 186         }
 187
 188         up_write(&fc->root->d_sb->s_umount);
 189         mnt = vfs_create_mount(fc);
 190         if (IS_ERR(mnt))
 191                 goto out_fc;
 192
 193         if (nfs_mountpoint_expiry_timeout < 0)
 194                 goto out_fc;
 195
 196         mntget(mnt); /* prevent immediate expiration */
 197         mnt_set_expiry(mnt, &nfs_automount_list);
 198         schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout);
 199
 200 out_fc:
 201         put_fs_context(fc);
 202         return mnt;
 203 }
 204
 205 static int
 206 nfs_namespace_getattr(const struct path *path, struct kstat *stat,
 207                         u32 request_mask, unsigned int query_flags)
 208 {
 209         if (NFS_FH(d_inode(path->dentry))->size != 0)
 210                 return nfs_getattr(path, stat, request_mask, query_flags);
 211         generic_fillattr(d_inode(path->dentry), stat);
 212         return 0;
 213 }
 214
 215 static int
 216 nfs_namespace_setattr(struct dentry *dentry, struct iattr *attr)
 217 {
 218         if (NFS_FH(d_inode(dentry))->size != 0)
 219                 return nfs_setattr(dentry, attr);
 220         return -EACCES;
 221 }
 222
 223 const struct inode_operations nfs_mountpoint_inode_operations = {
 224         .getattr        = nfs_getattr,
 225         .setattr        = nfs_setattr,
 226 };
 227
 228 const struct inode_operations nfs_referral_inode_operations = {
 229         .getattr        = nfs_namespace_getattr,
 230         .setattr        = nfs_namespace_setattr,
 231 };
 232
 233 static void nfs_expire_automounts(struct work_struct *work)
 234 {
 235         struct list_head *list = &nfs_automount_list;
 236
 237         mark_mounts_for_expiry(list);
 238         if (!list_empty(list))
 239                 schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout);
 240 }
 241
 242 void nfs_release_automount_timer(void)
 243 {
 244         if (list_empty(&nfs_automount_list))
 245                 cancel_delayed_work(&nfs_automount_task);
 246 }
 247
 248 /**
 249  * nfs_do_submount - set up mountpoint when crossing a filesystem boundary
 250  * @dentry: parent directory
 251  * @fh: filehandle for new root dentry
 252  * @fattr: attributes for new root inode
 253  * @authflavor: security flavor to use when performing the mount
 254  *
 255  */
 256 int nfs_do_submount(struct fs_context *fc)
 257 {
 258         struct nfs_fs_context *ctx = nfs_fc2context(fc);
 259         struct dentry *dentry = ctx->clone_data.dentry;
 260         struct nfs_server *server;
 261         char *buffer, *p;
 262         int ret;
 263
 264         /* create a new volume representation */
 265         server = ctx->nfs_mod->rpc_ops->clone_server(NFS_SB(ctx->clone_data.sb),
 266                                                      ctx->mntfh,
 267                                                      ctx->clone_data.fattr,
 268                                                      ctx->selected_flavor);
 269
 270         if (IS_ERR(server))
 271                 return PTR_ERR(server);
 272
 273         ctx->server = server;
 274
 275         buffer = kmalloc(4096, GFP_USER);
 276         if (!buffer)
 277                 return -ENOMEM;
 278
 279         ctx->internal           = true;
 280         ctx->clone_data.inherited_bsize = ctx->clone_data.sb->s_blocksize_bits;
 281
 282         p = nfs_devname(dentry, buffer, 4096);
 283         if (IS_ERR(p)) {
 284                 nfs_errorf(fc, "NFS: Couldn't determine submount pathname");
 285                 ret = PTR_ERR(p);
 286         } else {
 287                 ret = vfs_parse_fs_string(fc, "source", p, buffer + 4096 - p);
 288                 if (!ret)
 289                         ret = vfs_get_tree(fc);
 290         }
 291         kfree(buffer);
 292         return ret;
 293 }
 294 EXPORT_SYMBOL_GPL(nfs_do_submount);
 295
 296 int nfs_submount(struct fs_context *fc, struct nfs_server *server)
 297 {
 298         struct nfs_fs_context *ctx = nfs_fc2context(fc);
 299         struct dentry *dentry = ctx->clone_data.dentry;
 300         struct dentry *parent = dget_parent(dentry);
 301         int err;
 302
 303         /* Look it up again to get its attributes */
 304         err = server->nfs_client->rpc_ops->lookup(d_inode(parent), dentry,
 305                                                   ctx->mntfh, ctx->clone_data.fattr,
 306                                                   NULL);
 307         dput(parent);
 308         if (err != 0)
 309                 return err;
 310
 311         ctx->selected_flavor = server->client->cl_auth->au_flavor;
 312         return nfs_do_submount(fc);
 313 }
 314 EXPORT_SYMBOL_GPL(nfs_submount);