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);
  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         int ret;
 118
 119         /* Names prefixed with a dot are R/W mounts. */
 120         if (name[0] == '.') {
 121                 if (len == 1)
 122                         return -EINVAL;
 123                 name++;
 124                 len--;
 125         }
 126
 127         cell = afs_find_cell(net, name, len, afs_cell_trace_use_probe);
 128         if (!IS_ERR(cell)) {
 129                 afs_unuse_cell(net, cell, afs_cell_trace_unuse_probe);
 130                 return 0;
 131         }
 132
 133         ret = dns_query(net->net, "afsdb", name, len, "srv=1",
 134                         NULL, NULL, false);
 135         if (ret == -ENODATA)
 136                 ret = -EDESTADDRREQ;
 137         return ret;
 138 }
 139
 140 /*
 141  * Try to auto mount the mountpoint with pseudo directory, if the autocell
 142  * operation is setted.
 143  */
 144 struct inode *afs_try_auto_mntpt(struct dentry *dentry, struct inode *dir)
 145 {
 146         struct afs_vnode *vnode = AFS_FS_I(dir);
 147         struct inode *inode;
 148         int ret = -ENOENT;
 149
 150         _enter("%p{%pd}, {%llx:%llu}",
 151                dentry, dentry, vnode->fid.vid, vnode->fid.vnode);
 152
 153         if (!test_bit(AFS_VNODE_AUTOCELL, &vnode->flags))
 154                 goto out;
 155
 156         ret = afs_probe_cell_name(dentry);
 157         if (ret < 0)
 158                 goto out;
 159
 160         inode = afs_iget_pseudo_dir(dir->i_sb, false);
 161         if (IS_ERR(inode)) {
 162                 ret = PTR_ERR(inode);
 163                 goto out;
 164         }
 165
 166         _leave("= %p", inode);
 167         return inode;
 168
 169 out:
 170         _leave("= %d", ret);
 171         return ret == -ENOENT ? NULL : ERR_PTR(ret);
 172 }
 173
 174 /*
 175  * Look up @cell in a dynroot directory.  This is a substitution for the
 176  * local cell name for the net namespace.
 177  */
 178 static struct dentry *afs_lookup_atcell(struct dentry *dentry)
 179 {
 180         struct afs_cell *cell;
 181         struct afs_net *net = afs_d2net(dentry);
 182         struct dentry *ret;
 183         char *name;
 184         int len;
 185
 186         if (!net->ws_cell)
 187                 return ERR_PTR(-ENOENT);
 188
 189         ret = ERR_PTR(-ENOMEM);
 190         name = kmalloc(AFS_MAXCELLNAME + 1, GFP_KERNEL);
 191         if (!name)
 192                 goto out_p;
 193
 194         down_read(&net->cells_lock);
 195         cell = net->ws_cell;
 196         if (cell) {
 197                 len = cell->name_len;
 198                 memcpy(name, cell->name, len + 1);
 199         }
 200         up_read(&net->cells_lock);
 201
 202         ret = ERR_PTR(-ENOENT);
 203         if (!cell)
 204                 goto out_n;
 205
 206         ret = lookup_one_len(name, dentry->d_parent, len);
 207
 208         /* We don't want to d_add() the @cell dentry here as we don't want to
 209          * the cached dentry to hide changes to the local cell name.
 210          */
 211
 212 out_n:
 213         kfree(name);
 214 out_p:
 215         return ret;
 216 }
 217
 218 /*
 219  * Look up an entry in a dynroot directory.
 220  */
 221 static struct dentry *afs_dynroot_lookup(struct inode *dir, struct dentry *dentry,
 222                                          unsigned int flags)
 223 {
 224         _enter("%pd", dentry);
 225
 226         ASSERTCMP(d_inode(dentry), ==, NULL);
 227
 228         if (flags & LOOKUP_CREATE)
 229                 return ERR_PTR(-EOPNOTSUPP);
 230
 231         if (dentry->d_name.len >= AFSNAMEMAX) {
 232                 _leave(" = -ENAMETOOLONG");
 233                 return ERR_PTR(-ENAMETOOLONG);
 234         }
 235
 236         if (dentry->d_name.len == 5 &&
 237             memcmp(dentry->d_name.name, "@cell", 5) == 0)
 238                 return afs_lookup_atcell(dentry);
 239
 240         return d_splice_alias(afs_try_auto_mntpt(dentry, dir), dentry);
 241 }
 242
 243 const struct inode_operations afs_dynroot_inode_operations = {
 244         .lookup         = afs_dynroot_lookup,
 245 };
 246
 247 /*
 248  * Dirs in the dynamic root don't need revalidation.
 249  */
 250 static int afs_dynroot_d_revalidate(struct dentry *dentry, unsigned int flags)
 251 {
 252         return 1;
 253 }
 254
 255 /*
 256  * Allow the VFS to enquire as to whether a dentry should be unhashed (mustn't
 257  * sleep)
 258  * - called from dput() when d_count is going to 0.
 259  * - return 1 to request dentry be unhashed, 0 otherwise
 260  */
 261 static int afs_dynroot_d_delete(const struct dentry *dentry)
 262 {
 263         return d_really_is_positive(dentry);
 264 }
 265
 266 const struct dentry_operations afs_dynroot_dentry_operations = {
 267         .d_revalidate   = afs_dynroot_d_revalidate,
 268         .d_delete       = afs_dynroot_d_delete,
 269         .d_release      = afs_d_release,
 270         .d_automount    = afs_d_automount,
 271 };
 272
 273 /*
 274  * Create a manually added cell mount directory.
 275  * - The caller must hold net->proc_cells_lock
 276  */
 277 int afs_dynroot_mkdir(struct afs_net *net, struct afs_cell *cell)
 278 {
 279         struct super_block *sb = net->dynroot_sb;
 280         struct dentry *root, *subdir;
 281         int ret;
 282
 283         if (!sb || atomic_read(&sb->s_active) == 0)
 284                 return 0;
 285
 286         /* Let the ->lookup op do the creation */
 287         root = sb->s_root;
 288         inode_lock(root->d_inode);
 289         subdir = lookup_one_len(cell->name, root, cell->name_len);
 290         if (IS_ERR(subdir)) {
 291                 ret = PTR_ERR(subdir);
 292                 goto unlock;
 293         }
 294
 295         /* Note that we're retaining an extra ref on the dentry */
 296         subdir->d_fsdata = (void *)1UL;
 297         ret = 0;
 298 unlock:
 299         inode_unlock(root->d_inode);
 300         return ret;
 301 }
 302
 303 /*
 304  * Remove a manually added cell mount directory.
 305  * - The caller must hold net->proc_cells_lock
 306  */
 307 void afs_dynroot_rmdir(struct afs_net *net, struct afs_cell *cell)
 308 {
 309         struct super_block *sb = net->dynroot_sb;
 310         struct dentry *root, *subdir;
 311
 312         if (!sb || atomic_read(&sb->s_active) == 0)
 313                 return;
 314
 315         root = sb->s_root;
 316         inode_lock(root->d_inode);
 317
 318         /* Don't want to trigger a lookup call, which will re-add the cell */
 319         subdir = try_lookup_one_len(cell->name, root, cell->name_len);
 320         if (IS_ERR_OR_NULL(subdir)) {
 321                 _debug("lookup %ld", PTR_ERR(subdir));
 322                 goto no_dentry;
 323         }
 324
 325         _debug("rmdir %pd %u", subdir, d_count(subdir));
 326
 327         if (subdir->d_fsdata) {
 328                 _debug("unpin %u", d_count(subdir));
 329                 subdir->d_fsdata = NULL;
 330                 dput(subdir);
 331         }
 332         dput(subdir);
 333 no_dentry:
 334         inode_unlock(root->d_inode);
 335         _leave("");
 336 }
 337
 338 /*
 339  * Populate a newly created dynamic root with cell names.
 340  */
 341 int afs_dynroot_populate(struct super_block *sb)
 342 {
 343         struct afs_cell *cell;
 344         struct afs_net *net = afs_sb2net(sb);
 345         int ret;
 346
 347         mutex_lock(&net->proc_cells_lock);
 348
 349         net->dynroot_sb = sb;
 350         hlist_for_each_entry(cell, &net->proc_cells, proc_link) {
 351                 ret = afs_dynroot_mkdir(net, cell);
 352                 if (ret < 0)
 353                         goto error;
 354         }
 355
 356         ret = 0;
 357 out:
 358         mutex_unlock(&net->proc_cells_lock);
 359         return ret;
 360
 361 error:
 362         net->dynroot_sb = NULL;
 363         goto out;
 364 }
 365
 366 /*
 367  * When a dynamic root that's in the process of being destroyed, depopulate it
 368  * of pinned directories.
 369  */
 370 void afs_dynroot_depopulate(struct super_block *sb)
 371 {
 372         struct afs_net *net = afs_sb2net(sb);
 373         struct dentry *root = sb->s_root, *subdir, *tmp;
 374
 375         /* Prevent more subdirs from being created */
 376         mutex_lock(&net->proc_cells_lock);
 377         if (net->dynroot_sb == sb)
 378                 net->dynroot_sb = NULL;
 379         mutex_unlock(&net->proc_cells_lock);
 380
 381         if (root) {
 382                 inode_lock(root->d_inode);
 383
 384                 /* Remove all the pins for dirs created for manually added cells */
 385                 list_for_each_entry_safe(subdir, tmp, &root->d_subdirs, d_child) {
 386                         if (subdir->d_fsdata) {
 387                                 subdir->d_fsdata = NULL;
 388                                 dput(subdir);
 389                         }
 390                 }
 391
 392                 inode_unlock(root->d_inode);
 393         }
 394 }