fs/afs/dynroot.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /* AFS dynamic root handling
   3  *
   4  * Copyright (C) 2018 Red Hat, Inc. All Rights Reserved.
   5  * Written by David Howells (dhowells@redhat.com)
   6  */
   7
   8 #include <linux/fs.h>
   9 #include <linux/namei.h>
  10 #include <linux/dns_resolver.h>
  11 #include "internal.h"
  12
  13 static atomic_t afs_autocell_ino;
  14
  15 /*
  16  * iget5() comparator for inode created by autocell operations
  17  *
  18  * These pseudo inodes don't match anything.
  19  */
  20 static int afs_iget5_pseudo_test(struct inode *inode, void *opaque)
  21 {
  22         return 0;
  23 }
  24
  25 /*
  26  * iget5() inode initialiser
  27  */
  28 static int afs_iget5_pseudo_set(struct inode *inode, void *opaque)
  29 {
  30         struct afs_super_info *as = AFS_FS_S(inode->i_sb);
  31         struct afs_vnode *vnode = AFS_FS_I(inode);
  32         struct afs_fid *fid = opaque;
  33
  34         vnode->volume           = as->volume;
  35         vnode->fid              = *fid;
  36         inode->i_ino            = fid->vnode;
  37         inode->i_generation     = fid->unique;
  38         return 0;
  39 }
  40
  41 /*
  42  * Create an inode for a dynamic root directory or an autocell dynamic
  43  * automount dir.
  44  */
  45 struct inode *afs_iget_pseudo_dir(struct super_block *sb, bool root)
  46 {
  47         struct afs_super_info *as = AFS_FS_S(sb);
  48         struct afs_vnode *vnode;
  49         struct inode *inode;
  50         struct afs_fid fid = {};
  51
  52         _enter("");
  53
  54         if (as->volume)
  55                 fid.vid = as->volume->vid;
  56         if (root) {
  57                 fid.vnode = 1;
  58                 fid.unique = 1;
  59         } else {
  60                 fid.vnode = atomic_inc_return(&afs_autocell_ino);
  61                 fid.unique = 0;
  62         }
  63
  64         inode = iget5_locked(sb, fid.vnode,
  65                              afs_iget5_pseudo_test, afs_iget5_pseudo_set, &fid);
  66         if (!inode) {
  67                 _leave(" = -ENOMEM");
  68                 return ERR_PTR(-ENOMEM);
  69         }
  70
  71         _debug("GOT INODE %p { ino=%lu, vl=%llx, vn=%llx, u=%x }",
  72                inode, inode->i_ino, fid.vid, fid.vnode, fid.unique);
  73
  74         vnode = AFS_FS_I(inode);
  75
  76         /* there shouldn't be an existing inode */
  77         BUG_ON(!(inode->i_state & I_NEW));
  78
  79         netfs_inode_init(&vnode->netfs, NULL, false);
  80         inode->i_size           = 0;
  81         inode->i_mode           = S_IFDIR | S_IRUGO | S_IXUGO;
  82         if (root) {
  83                 inode->i_op     = &afs_dynroot_inode_operations;
  84                 inode->i_fop    = &simple_dir_operations;
  85         } else {
  86                 inode->i_op     = &afs_autocell_inode_operations;
  87         }
  88         set_nlink(inode, 2);
  89         inode->i_uid            = GLOBAL_ROOT_UID;
  90         inode->i_gid            = GLOBAL_ROOT_GID;
  91         simple_inode_init_ts(inode);
  92         inode->i_blocks         = 0;
  93         inode->i_generation     = 0;
  94
  95         set_bit(AFS_VNODE_PSEUDODIR, &vnode->flags);
  96         if (!root) {
  97                 set_bit(AFS_VNODE_MOUNTPOINT, &vnode->flags);
  98                 inode->i_flags |= S_AUTOMOUNT;
  99         }
 100
 101         inode->i_flags |= S_NOATIME;
 102         unlock_new_inode(inode);
 103         _leave(" = %p", inode);
 104         return inode;
 105 }
 106
 107 /*
 108  * Probe to see if a cell may exist.  This prevents positive dentries from
 109  * being created unnecessarily.
 110  */
 111 static int afs_probe_cell_name(struct dentry *dentry)
 112 {
 113         struct afs_cell *cell;
 114         struct afs_net *net = afs_d2net(dentry);
 115         const char *name = dentry->d_name.name;
 116         size_t len = dentry->d_name.len;
 117         char *result = NULL;
 118         int ret;
 119
 120         /* Names prefixed with a dot are R/W mounts. */
 121         if (name[0] == '.') {
 122                 if (len == 1)
 123                         return -EINVAL;
 124                 name++;
 125                 len--;
 126         }
 127
 128         cell = afs_find_cell(net, name, len, afs_cell_trace_use_probe);
 129         if (!IS_ERR(cell)) {
 130                 afs_unuse_cell(net, cell, afs_cell_trace_unuse_probe);
 131                 return 0;
 132         }
 133
 134         ret = dns_query(net->net, "afsdb", name, len, "srv=1",
 135                         &result, NULL, false);
 136         if (ret == -ENODATA || ret == -ENOKEY || ret == 0)
 137                 ret = -ENOENT;
 138         if (ret > 0 && ret >= sizeof(struct dns_server_list_v1_header)) {
 139                 struct dns_server_list_v1_header *v1 = (void *)result;
 140
 141                 if (v1->hdr.zero == 0 &&
 142                     v1->hdr.content == DNS_PAYLOAD_IS_SERVER_LIST &&
 143                     v1->hdr.version == 1 &&
 144                     (v1->status != DNS_LOOKUP_GOOD &&
 145                      v1->status != DNS_LOOKUP_GOOD_WITH_BAD))
 146                         return -ENOENT;
 147
 148         }
 149
 150         kfree(result);
 151         return ret;
 152 }
 153
 154 /*
 155  * Try to auto mount the mountpoint with pseudo directory, if the autocell
 156  * operation is setted.
 157  */
 158 struct inode *afs_try_auto_mntpt(struct dentry *dentry, struct inode *dir)
 159 {
 160         struct afs_vnode *vnode = AFS_FS_I(dir);
 161         struct inode *inode;
 162         int ret = -ENOENT;
 163
 164         _enter("%p{%pd}, {%llx:%llu}",
 165                dentry, dentry, vnode->fid.vid, vnode->fid.vnode);
 166
 167         if (!test_bit(AFS_VNODE_AUTOCELL, &vnode->flags))
 168                 goto out;
 169
 170         ret = afs_probe_cell_name(dentry);
 171         if (ret < 0)
 172                 goto out;
 173
 174         inode = afs_iget_pseudo_dir(dir->i_sb, false);
 175         if (IS_ERR(inode)) {
 176                 ret = PTR_ERR(inode);
 177                 goto out;
 178         }
 179
 180         _leave("= %p", inode);
 181         return inode;
 182
 183 out:
 184         _leave("= %d", ret);
 185         return ret == -ENOENT ? NULL : ERR_PTR(ret);
 186 }
 187
 188 /*
 189  * Look up @cell in a dynroot directory.  This is a substitution for the
 190  * local cell name for the net namespace.
 191  */
 192 static struct dentry *afs_lookup_atcell(struct dentry *dentry)
 193 {
 194         struct afs_cell *cell;
 195         struct afs_net *net = afs_d2net(dentry);
 196         struct dentry *ret;
 197         char *name;
 198         int len;
 199
 200         if (!net->ws_cell)
 201                 return ERR_PTR(-ENOENT);
 202
 203         ret = ERR_PTR(-ENOMEM);
 204         name = kmalloc(AFS_MAXCELLNAME + 1, GFP_KERNEL);
 205         if (!name)
 206                 goto out_p;
 207
 208         down_read(&net->cells_lock);
 209         cell = net->ws_cell;
 210         if (cell) {
 211                 len = cell->name_len;
 212                 memcpy(name, cell->name, len + 1);
 213         }
 214         up_read(&net->cells_lock);
 215
 216         ret = ERR_PTR(-ENOENT);
 217         if (!cell)
 218                 goto out_n;
 219
 220         ret = lookup_one_len(name, dentry->d_parent, len);
 221
 222         /* We don't want to d_add() the @cell dentry here as we don't want to
 223          * the cached dentry to hide changes to the local cell name.
 224          */
 225
 226 out_n:
 227         kfree(name);
 228 out_p:
 229         return ret;
 230 }
 231
 232 /*
 233  * Look up an entry in a dynroot directory.
 234  */
 235 static struct dentry *afs_dynroot_lookup(struct inode *dir, struct dentry *dentry,
 236                                          unsigned int flags)
 237 {
 238         _enter("%pd", dentry);
 239
 240         ASSERTCMP(d_inode(dentry), ==, NULL);
 241
 242         if (flags & LOOKUP_CREATE)
 243                 return ERR_PTR(-EOPNOTSUPP);
 244
 245         if (dentry->d_name.len >= AFSNAMEMAX) {
 246                 _leave(" = -ENAMETOOLONG");
 247                 return ERR_PTR(-ENAMETOOLONG);
 248         }
 249
 250         if (dentry->d_name.len == 5 &&
 251             memcmp(dentry->d_name.name, "@cell", 5) == 0)
 252                 return afs_lookup_atcell(dentry);
 253
 254         return d_splice_alias(afs_try_auto_mntpt(dentry, dir), dentry);
 255 }
 256
 257 const struct inode_operations afs_dynroot_inode_operations = {
 258         .lookup         = afs_dynroot_lookup,
 259 };
 260
 261 const struct dentry_operations afs_dynroot_dentry_operations = {
 262         .d_delete       = always_delete_dentry,
 263         .d_release      = afs_d_release,
 264         .d_automount    = afs_d_automount,
 265 };
 266
 267 /*
 268  * Create a manually added cell mount directory.
 269  * - The caller must hold net->proc_cells_lock
 270  */
 271 int afs_dynroot_mkdir(struct afs_net *net, struct afs_cell *cell)
 272 {
 273         struct super_block *sb = net->dynroot_sb;
 274         struct dentry *root, *subdir;
 275         int ret;
 276
 277         if (!sb || atomic_read(&sb->s_active) == 0)
 278                 return 0;
 279
 280         /* Let the ->lookup op do the creation */
 281         root = sb->s_root;
 282         inode_lock(root->d_inode);
 283         subdir = lookup_one_len(cell->name, root, cell->name_len);
 284         if (IS_ERR(subdir)) {
 285                 ret = PTR_ERR(subdir);
 286                 goto unlock;
 287         }
 288
 289         /* Note that we're retaining an extra ref on the dentry */
 290         subdir->d_fsdata = (void *)1UL;
 291         ret = 0;
 292 unlock:
 293         inode_unlock(root->d_inode);
 294         return ret;
 295 }
 296
 297 /*
 298  * Remove a manually added cell mount directory.
 299  * - The caller must hold net->proc_cells_lock
 300  */
 301 void afs_dynroot_rmdir(struct afs_net *net, struct afs_cell *cell)
 302 {
 303         struct super_block *sb = net->dynroot_sb;
 304         struct dentry *root, *subdir;
 305
 306         if (!sb || atomic_read(&sb->s_active) == 0)
 307                 return;
 308
 309         root = sb->s_root;
 310         inode_lock(root->d_inode);
 311
 312         /* Don't want to trigger a lookup call, which will re-add the cell */
 313         subdir = try_lookup_one_len(cell->name, root, cell->name_len);
 314         if (IS_ERR_OR_NULL(subdir)) {
 315                 _debug("lookup %ld", PTR_ERR(subdir));
 316                 goto no_dentry;
 317         }
 318
 319         _debug("rmdir %pd %u", subdir, d_count(subdir));
 320
 321         if (subdir->d_fsdata) {
 322                 _debug("unpin %u", d_count(subdir));
 323                 subdir->d_fsdata = NULL;
 324                 dput(subdir);
 325         }
 326         dput(subdir);
 327 no_dentry:
 328         inode_unlock(root->d_inode);
 329         _leave("");
 330 }
 331
 332 /*
 333  * Populate a newly created dynamic root with cell names.
 334  */
 335 int afs_dynroot_populate(struct super_block *sb)
 336 {
 337         struct afs_cell *cell;
 338         struct afs_net *net = afs_sb2net(sb);
 339         int ret;
 340
 341         mutex_lock(&net->proc_cells_lock);
 342
 343         net->dynroot_sb = sb;
 344         hlist_for_each_entry(cell, &net->proc_cells, proc_link) {
 345                 ret = afs_dynroot_mkdir(net, cell);
 346                 if (ret < 0)
 347                         goto error;
 348         }
 349
 350         ret = 0;
 351 out:
 352         mutex_unlock(&net->proc_cells_lock);
 353         return ret;
 354
 355 error:
 356         net->dynroot_sb = NULL;
 357         goto out;
 358 }
 359
 360 /*
 361  * When a dynamic root that's in the process of being destroyed, depopulate it
 362  * of pinned directories.
 363  */
 364 void afs_dynroot_depopulate(struct super_block *sb)
 365 {
 366         struct afs_net *net = afs_sb2net(sb);
 367         struct dentry *root = sb->s_root, *subdir;
 368
 369         /* Prevent more subdirs from being created */
 370         mutex_lock(&net->proc_cells_lock);
 371         if (net->dynroot_sb == sb)
 372                 net->dynroot_sb = NULL;
 373         mutex_unlock(&net->proc_cells_lock);
 374
 375         if (root) {
 376                 struct hlist_node *n;
 377                 inode_lock(root->d_inode);
 378
 379                 /* Remove all the pins for dirs created for manually added cells */
 380                 hlist_for_each_entry_safe(subdir, n, &root->d_children, d_sib) {
 381                         if (subdir->d_fsdata) {
 382                                 subdir->d_fsdata = NULL;
 383                                 dput(subdir);
 384                         }
 385                 }
 386
 387                 inode_unlock(root->d_inode);
 388         }
 389 }