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