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 #define AFS_MIN_DYNROOT_CELL_INO 4 /* Allow for ., .., @cell, .@cell */ 14 #define AFS_MAX_DYNROOT_CELL_INO ((unsigned int)INT_MAX) 15 16 static struct dentry *afs_lookup_atcell(struct inode *dir, struct dentry *dentry, ino_t ino); 17 18 /* 19 * iget5() comparator for inode created by autocell operations 20 */ 21 static int afs_iget5_pseudo_test(struct inode *inode, void *opaque) 22 { 23 struct afs_fid *fid = opaque; 24 25 return inode->i_ino == fid->vnode; 26 } 27 28 /* 29 * iget5() inode initialiser 30 */ 31 static int afs_iget5_pseudo_set(struct inode *inode, void *opaque) 32 { 33 struct afs_super_info *as = AFS_FS_S(inode->i_sb); 34 struct afs_vnode *vnode = AFS_FS_I(inode); 35 struct afs_fid *fid = opaque; 36 37 vnode->volume = as->volume; 38 vnode->fid = *fid; 39 inode->i_ino = fid->vnode; 40 inode->i_generation = fid->unique; 41 return 0; 42 } 43 44 /* 45 * Create an inode for an autocell dynamic automount dir. 46 */ 47 static struct inode *afs_iget_pseudo_dir(struct super_block *sb, ino_t ino) 48 { 49 struct afs_vnode *vnode; 50 struct inode *inode; 51 struct afs_fid fid = { .vnode = ino, .unique = 1, }; 52 53 _enter(""); 54 55 inode = iget5_locked(sb, fid.vnode, 56 afs_iget5_pseudo_test, afs_iget5_pseudo_set, &fid); 57 if (!inode) { 58 _leave(" = -ENOMEM"); 59 return ERR_PTR(-ENOMEM); 60 } 61 62 _debug("GOT INODE %p { ino=%lu, vl=%llx, vn=%llx, u=%x }", 63 inode, inode->i_ino, fid.vid, fid.vnode, fid.unique); 64 65 vnode = AFS_FS_I(inode); 66 67 if (inode->i_state & I_NEW) { 68 netfs_inode_init(&vnode->netfs, NULL, false); 69 simple_inode_init_ts(inode); 70 set_nlink(inode, 2); 71 inode->i_size = 0; 72 inode->i_mode = S_IFDIR | 0555; 73 inode->i_op = &afs_autocell_inode_operations; 74 inode->i_uid = GLOBAL_ROOT_UID; 75 inode->i_gid = GLOBAL_ROOT_GID; 76 inode->i_blocks = 0; 77 inode->i_generation = 0; 78 inode->i_flags |= S_AUTOMOUNT | S_NOATIME; 79 80 set_bit(AFS_VNODE_PSEUDODIR, &vnode->flags); 81 set_bit(AFS_VNODE_MOUNTPOINT, &vnode->flags); 82 83 unlock_new_inode(inode); 84 } 85 _leave(" = %p", inode); 86 return inode; 87 } 88 89 /* 90 * Try to automount the mountpoint with pseudo directory, if the autocell 91 * option is set. 92 */ 93 static struct dentry *afs_dynroot_lookup_cell(struct inode *dir, struct dentry *dentry, 94 unsigned int flags) 95 { 96 struct afs_cell *cell = NULL; 97 struct afs_net *net = afs_d2net(dentry); 98 struct inode *inode = NULL; 99 const char *name = dentry->d_name.name; 100 size_t len = dentry->d_name.len; 101 bool dotted = false; 102 int ret = -ENOENT; 103 104 /* Names prefixed with a dot are R/W mounts. */ 105 if (name[0] == '.') { 106 name++; 107 len--; 108 dotted = true; 109 } 110 111 cell = afs_lookup_cell(net, name, len, NULL, 112 AFS_LOOKUP_CELL_DYNROOT, 113 afs_cell_trace_use_lookup_dynroot); 114 if (IS_ERR(cell)) { 115 ret = PTR_ERR(cell); 116 goto out_no_cell; 117 } 118 119 inode = afs_iget_pseudo_dir(dir->i_sb, cell->dynroot_ino * 2 + dotted); 120 if (IS_ERR(inode)) { 121 ret = PTR_ERR(inode); 122 goto out; 123 } 124 125 dentry->d_fsdata = cell; 126 return d_splice_alias(inode, dentry); 127 128 out: 129 afs_unuse_cell(cell, afs_cell_trace_unuse_lookup_dynroot); 130 out_no_cell: 131 if (!inode) 132 return d_splice_alias(inode, dentry); 133 return ret == -ENOENT ? NULL : ERR_PTR(ret); 134 } 135 136 /* 137 * Look up an entry in a dynroot directory. 138 */ 139 static struct dentry *afs_dynroot_lookup(struct inode *dir, struct dentry *dentry, 140 unsigned int flags) 141 { 142 _enter("%pd", dentry); 143 144 if (flags & LOOKUP_CREATE) 145 return ERR_PTR(-EOPNOTSUPP); 146 147 if (dentry->d_name.len >= AFSNAMEMAX) { 148 _leave(" = -ENAMETOOLONG"); 149 return ERR_PTR(-ENAMETOOLONG); 150 } 151 152 if (dentry->d_name.len == 5 && 153 memcmp(dentry->d_name.name, "@cell", 5) == 0) 154 return afs_lookup_atcell(dir, dentry, 2); 155 156 if (dentry->d_name.len == 6 && 157 memcmp(dentry->d_name.name, ".@cell", 6) == 0) 158 return afs_lookup_atcell(dir, dentry, 3); 159 160 return afs_dynroot_lookup_cell(dir, dentry, flags); 161 } 162 163 const struct inode_operations afs_dynroot_inode_operations = { 164 .lookup = afs_dynroot_lookup, 165 }; 166 167 static void afs_dynroot_d_release(struct dentry *dentry) 168 { 169 struct afs_cell *cell = dentry->d_fsdata; 170 171 afs_unuse_cell(cell, afs_cell_trace_unuse_dynroot_mntpt); 172 } 173 174 /* 175 * Keep @cell symlink dentries around, but only keep cell autodirs when they're 176 * being used. 177 */ 178 static int afs_dynroot_delete_dentry(const struct dentry *dentry) 179 { 180 const struct qstr *name = &dentry->d_name; 181 182 if (name->len == 5 && memcmp(name->name, "@cell", 5) == 0) 183 return 0; 184 if (name->len == 6 && memcmp(name->name, ".@cell", 6) == 0) 185 return 0; 186 return 1; 187 } 188 189 const struct dentry_operations afs_dynroot_dentry_operations = { 190 .d_delete = afs_dynroot_delete_dentry, 191 .d_release = afs_dynroot_d_release, 192 .d_automount = afs_d_automount, 193 }; 194 195 static void afs_atcell_delayed_put_cell(void *arg) 196 { 197 struct afs_cell *cell = arg; 198 199 afs_put_cell(cell, afs_cell_trace_put_atcell); 200 } 201 202 /* 203 * Read @cell or .@cell symlinks. 204 */ 205 static const char *afs_atcell_get_link(struct dentry *dentry, struct inode *inode, 206 struct delayed_call *done) 207 { 208 struct afs_vnode *vnode = AFS_FS_I(inode); 209 struct afs_cell *cell; 210 struct afs_net *net = afs_i2net(inode); 211 const char *name; 212 bool dotted = vnode->fid.vnode == 3; 213 214 if (!rcu_access_pointer(net->ws_cell)) 215 return ERR_PTR(-ENOENT); 216 217 if (!dentry) { 218 /* We're in RCU-pathwalk. */ 219 cell = rcu_dereference(net->ws_cell); 220 if (dotted) 221 name = cell->name - 1; 222 else 223 name = cell->name; 224 /* Shouldn't need to set a delayed call. */ 225 return name; 226 } 227 228 down_read(&net->cells_lock); 229 230 cell = rcu_dereference_protected(net->ws_cell, lockdep_is_held(&net->cells_lock)); 231 if (dotted) 232 name = cell->name - 1; 233 else 234 name = cell->name; 235 afs_get_cell(cell, afs_cell_trace_get_atcell); 236 set_delayed_call(done, afs_atcell_delayed_put_cell, cell); 237 238 up_read(&net->cells_lock); 239 return name; 240 } 241 242 static const struct inode_operations afs_atcell_inode_operations = { 243 .get_link = afs_atcell_get_link, 244 }; 245 246 /* 247 * Create an inode for the @cell or .@cell symlinks. 248 */ 249 static struct dentry *afs_lookup_atcell(struct inode *dir, struct dentry *dentry, ino_t ino) 250 { 251 struct afs_vnode *vnode; 252 struct inode *inode; 253 struct afs_fid fid = { .vnode = ino, .unique = 1, }; 254 255 inode = iget5_locked(dir->i_sb, fid.vnode, 256 afs_iget5_pseudo_test, afs_iget5_pseudo_set, &fid); 257 if (!inode) 258 return ERR_PTR(-ENOMEM); 259 260 vnode = AFS_FS_I(inode); 261 262 if (inode->i_state & I_NEW) { 263 netfs_inode_init(&vnode->netfs, NULL, false); 264 simple_inode_init_ts(inode); 265 set_nlink(inode, 1); 266 inode->i_size = 0; 267 inode->i_mode = S_IFLNK | 0555; 268 inode->i_op = &afs_atcell_inode_operations; 269 inode->i_uid = GLOBAL_ROOT_UID; 270 inode->i_gid = GLOBAL_ROOT_GID; 271 inode->i_blocks = 0; 272 inode->i_generation = 0; 273 inode->i_flags |= S_NOATIME; 274 275 unlock_new_inode(inode); 276 } 277 return d_splice_alias(inode, dentry); 278 } 279 280 /* 281 * Transcribe the cell database into readdir content under the RCU read lock. 282 * Each cell produces two entries, one prefixed with a dot and one not. 283 */ 284 static int afs_dynroot_readdir_cells(struct afs_net *net, struct dir_context *ctx) 285 { 286 const struct afs_cell *cell; 287 loff_t newpos; 288 289 _enter("%llu", ctx->pos); 290 291 for (;;) { 292 unsigned int ix = ctx->pos >> 1; 293 294 cell = idr_get_next(&net->cells_dyn_ino, &ix); 295 if (!cell) 296 return 0; 297 if (READ_ONCE(cell->state) == AFS_CELL_REMOVING || 298 READ_ONCE(cell->state) == AFS_CELL_DEAD) { 299 ctx->pos += 2; 300 ctx->pos &= ~1; 301 continue; 302 } 303 304 newpos = ix << 1; 305 if (newpos > ctx->pos) 306 ctx->pos = newpos; 307 308 _debug("pos %llu -> cell %u", ctx->pos, cell->dynroot_ino); 309 310 if ((ctx->pos & 1) == 0) { 311 if (!dir_emit(ctx, cell->name, cell->name_len, 312 cell->dynroot_ino, DT_DIR)) 313 return 0; 314 ctx->pos++; 315 } 316 if ((ctx->pos & 1) == 1) { 317 if (!dir_emit(ctx, cell->name - 1, cell->name_len + 1, 318 cell->dynroot_ino + 1, DT_DIR)) 319 return 0; 320 ctx->pos++; 321 } 322 } 323 return 0; 324 } 325 326 /* 327 * Read the AFS dynamic root directory. This produces a list of cellnames, 328 * dotted and undotted, along with @cell and .@cell links if configured. 329 */ 330 static int afs_dynroot_readdir(struct file *file, struct dir_context *ctx) 331 { 332 struct afs_net *net = afs_d2net(file->f_path.dentry); 333 int ret = 0; 334 335 if (!dir_emit_dots(file, ctx)) 336 return 0; 337 338 if (ctx->pos == 2) { 339 if (rcu_access_pointer(net->ws_cell) && 340 !dir_emit(ctx, "@cell", 5, 2, DT_LNK)) 341 return 0; 342 ctx->pos = 3; 343 } 344 if (ctx->pos == 3) { 345 if (rcu_access_pointer(net->ws_cell) && 346 !dir_emit(ctx, ".@cell", 6, 3, DT_LNK)) 347 return 0; 348 ctx->pos = 4; 349 } 350 351 if ((unsigned long long)ctx->pos <= AFS_MAX_DYNROOT_CELL_INO) { 352 down_read(&net->cells_lock); 353 ret = afs_dynroot_readdir_cells(net, ctx); 354 up_read(&net->cells_lock); 355 } 356 return ret; 357 } 358 359 static const struct file_operations afs_dynroot_file_operations = { 360 .llseek = generic_file_llseek, 361 .read = generic_read_dir, 362 .iterate_shared = afs_dynroot_readdir, 363 .fsync = noop_fsync, 364 }; 365 366 /* 367 * Create an inode for a dynamic root directory. 368 */ 369 struct inode *afs_dynroot_iget_root(struct super_block *sb) 370 { 371 struct afs_super_info *as = AFS_FS_S(sb); 372 struct afs_vnode *vnode; 373 struct inode *inode; 374 struct afs_fid fid = { .vid = 0, .vnode = 1, .unique = 1,}; 375 376 if (as->volume) 377 fid.vid = as->volume->vid; 378 379 inode = iget5_locked(sb, fid.vnode, 380 afs_iget5_pseudo_test, afs_iget5_pseudo_set, &fid); 381 if (!inode) 382 return ERR_PTR(-ENOMEM); 383 384 vnode = AFS_FS_I(inode); 385 386 /* there shouldn't be an existing inode */ 387 if (inode->i_state & I_NEW) { 388 netfs_inode_init(&vnode->netfs, NULL, false); 389 simple_inode_init_ts(inode); 390 set_nlink(inode, 2); 391 inode->i_size = 0; 392 inode->i_mode = S_IFDIR | 0555; 393 inode->i_op = &afs_dynroot_inode_operations; 394 inode->i_fop = &afs_dynroot_file_operations; 395 inode->i_uid = GLOBAL_ROOT_UID; 396 inode->i_gid = GLOBAL_ROOT_GID; 397 inode->i_blocks = 0; 398 inode->i_generation = 0; 399 inode->i_flags |= S_NOATIME; 400 401 set_bit(AFS_VNODE_PSEUDODIR, &vnode->flags); 402 unlock_new_inode(inode); 403 } 404 _leave(" = %p", inode); 405 return inode; 406 } 407