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1/* dir.c: AFS dynamic root handling
2 *
3 * Copyright (C) 2018 Red Hat, Inc. All Rights Reserved.
4 * Written by David Howells (dhowells@redhat.com)
5 *
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public Licence
8 * as published by the Free Software Foundation; either version
9 * 2 of the Licence, or (at your option) any later version.
10 */
11
12#include <linux/fs.h>
13#include <linux/namei.h>
14#include <linux/dns_resolver.h>
15#include "internal.h"
16
17const struct file_operations afs_dynroot_file_operations = {
18 .open = dcache_dir_open,
19 .release = dcache_dir_close,
20 .iterate_shared = dcache_readdir,
21 .llseek = dcache_dir_lseek,
22};
23
24/*
25 * Probe to see if a cell may exist. This prevents positive dentries from
26 * being created unnecessarily.
27 */
28static int afs_probe_cell_name(struct dentry *dentry)
29{
30 struct afs_cell *cell;
31 const char *name = dentry->d_name.name;
32 size_t len = dentry->d_name.len;
33 int ret;
34
35 /* Names prefixed with a dot are R/W mounts. */
36 if (name[0] == '.') {
37 if (len == 1)
38 return -EINVAL;
39 name++;
40 len--;
41 }
42
43 cell = afs_lookup_cell_rcu(afs_d2net(dentry), name, len);
44 if (!IS_ERR(cell)) {
45 afs_put_cell(afs_d2net(dentry), cell);
46 return 0;
47 }
48
49 ret = dns_query("afsdb", name, len, "ipv4", NULL, NULL);
50 if (ret == -ENODATA)
51 ret = -EDESTADDRREQ;
52 return ret;
53}
54
55/*
56 * Try to auto mount the mountpoint with pseudo directory, if the autocell
57 * operation is setted.
58 */
59struct inode *afs_try_auto_mntpt(struct dentry *dentry, struct inode *dir)
60{
61 struct afs_vnode *vnode = AFS_FS_I(dir);
62 struct inode *inode;
63 int ret = -ENOENT;
64
65 _enter("%p{%pd}, {%x:%u}",
66 dentry, dentry, vnode->fid.vid, vnode->fid.vnode);
67
68 if (!test_bit(AFS_VNODE_AUTOCELL, &vnode->flags))
69 goto out;
70
71 ret = afs_probe_cell_name(dentry);
72 if (ret < 0)
73 goto out;
74
75 inode = afs_iget_pseudo_dir(dir->i_sb, false);
76 if (IS_ERR(inode)) {
77 ret = PTR_ERR(inode);
78 goto out;
79 }
80
81 _leave("= %p", inode);
82 return inode;
83
84out:
85 _leave("= %d", ret);
86 return ERR_PTR(ret);
87}
88
89/*
90 * Look up @cell in a dynroot directory. This is a substitution for the
91 * local cell name for the net namespace.
92 */
93static struct dentry *afs_lookup_atcell(struct dentry *dentry)
94{
95 struct afs_cell *cell;
96 struct afs_net *net = afs_d2net(dentry);
97 struct dentry *ret;
98 unsigned int seq = 0;
99 char *name;
100 int len;
101
102 if (!net->ws_cell)
103 return ERR_PTR(-ENOENT);
104
105 ret = ERR_PTR(-ENOMEM);
106 name = kmalloc(AFS_MAXCELLNAME + 1, GFP_KERNEL);
107 if (!name)
108 goto out_p;
109
110 rcu_read_lock();
111 do {
112 read_seqbegin_or_lock(&net->cells_lock, &seq);
113 cell = rcu_dereference_raw(net->ws_cell);
114 if (cell) {
115 len = cell->name_len;
116 memcpy(name, cell->name, len + 1);
117 }
118 } while (need_seqretry(&net->cells_lock, seq));
119 done_seqretry(&net->cells_lock, seq);
120 rcu_read_unlock();
121
122 ret = ERR_PTR(-ENOENT);
123 if (!cell)
124 goto out_n;
125
126 ret = lookup_one_len(name, dentry->d_parent, len);
127
128 /* We don't want to d_add() the @cell dentry here as we don't want to
129 * the cached dentry to hide changes to the local cell name.
130 */
131
132out_n:
133 kfree(name);
134out_p:
135 return ret;
136}
137
138/*
139 * Look up an entry in a dynroot directory.
140 */
141static struct dentry *afs_dynroot_lookup(struct inode *dir, struct dentry *dentry,
142 unsigned int flags)
143{
144 struct afs_vnode *vnode;
145 struct inode *inode;
146 int ret;
147
148 vnode = AFS_FS_I(dir);
149
150 _enter("%pd", dentry);
151
152 ASSERTCMP(d_inode(dentry), ==, NULL);
153
154 if (dentry->d_name.len >= AFSNAMEMAX) {
155 _leave(" = -ENAMETOOLONG");
156 return ERR_PTR(-ENAMETOOLONG);
157 }
158
159 if (dentry->d_name.len == 5 &&
160 memcmp(dentry->d_name.name, "@cell", 5) == 0)
161 return afs_lookup_atcell(dentry);
162
163 inode = afs_try_auto_mntpt(dentry, dir);
164 if (IS_ERR(inode)) {
165 ret = PTR_ERR(inode);
166 if (ret == -ENOENT) {
167 d_add(dentry, NULL);
168 _leave(" = NULL [negative]");
169 return NULL;
170 }
171 _leave(" = %d [do]", ret);
172 return ERR_PTR(ret);
173 }
174
175 d_add(dentry, inode);
176 _leave(" = 0 { ino=%lu v=%u }",
177 d_inode(dentry)->i_ino, d_inode(dentry)->i_generation);
178 return NULL;
179}
180
181const struct inode_operations afs_dynroot_inode_operations = {
182 .lookup = afs_dynroot_lookup,
183};
184
185/*
186 * Dirs in the dynamic root don't need revalidation.
187 */
188static int afs_dynroot_d_revalidate(struct dentry *dentry, unsigned int flags)
189{
190 return 1;
191}
192
193/*
194 * Allow the VFS to enquire as to whether a dentry should be unhashed (mustn't
195 * sleep)
196 * - called from dput() when d_count is going to 0.
197 * - return 1 to request dentry be unhashed, 0 otherwise
198 */
199static int afs_dynroot_d_delete(const struct dentry *dentry)
200{
201 return d_really_is_positive(dentry);
202}
203
204const struct dentry_operations afs_dynroot_dentry_operations = {
205 .d_revalidate = afs_dynroot_d_revalidate,
206 .d_delete = afs_dynroot_d_delete,
207 .d_release = afs_d_release,
208 .d_automount = afs_d_automount,
209};
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
13static 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 */
20static int afs_iget5_pseudo_test(struct inode *inode, void *opaque)
21{
22 return 0;
23}
24
25/*
26 * iget5() inode initialiser
27 */
28static 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 */
45struct 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 inode->i_size = 0;
80 inode->i_mode = S_IFDIR | S_IRUGO | S_IXUGO;
81 if (root) {
82 inode->i_op = &afs_dynroot_inode_operations;
83 inode->i_fop = &simple_dir_operations;
84 } else {
85 inode->i_op = &afs_autocell_inode_operations;
86 }
87 set_nlink(inode, 2);
88 inode->i_uid = GLOBAL_ROOT_UID;
89 inode->i_gid = GLOBAL_ROOT_GID;
90 inode->i_ctime = inode->i_atime = inode->i_mtime = current_time(inode);
91 inode->i_blocks = 0;
92 inode->i_generation = 0;
93
94 set_bit(AFS_VNODE_PSEUDODIR, &vnode->flags);
95 if (!root) {
96 set_bit(AFS_VNODE_MOUNTPOINT, &vnode->flags);
97 inode->i_flags |= S_AUTOMOUNT;
98 }
99
100 inode->i_flags |= S_NOATIME;
101 unlock_new_inode(inode);
102 _leave(" = %p", inode);
103 return inode;
104}
105
106/*
107 * Probe to see if a cell may exist. This prevents positive dentries from
108 * being created unnecessarily.
109 */
110static int afs_probe_cell_name(struct dentry *dentry)
111{
112 struct afs_cell *cell;
113 struct afs_net *net = afs_d2net(dentry);
114 const char *name = dentry->d_name.name;
115 size_t len = dentry->d_name.len;
116 int ret;
117
118 /* Names prefixed with a dot are R/W mounts. */
119 if (name[0] == '.') {
120 if (len == 1)
121 return -EINVAL;
122 name++;
123 len--;
124 }
125
126 cell = afs_lookup_cell_rcu(net, name, len);
127 if (!IS_ERR(cell)) {
128 afs_put_cell(net, cell);
129 return 0;
130 }
131
132 ret = dns_query(net->net, "afsdb", name, len, "srv=1",
133 NULL, NULL, false);
134 if (ret == -ENODATA)
135 ret = -EDESTADDRREQ;
136 return ret;
137}
138
139/*
140 * Try to auto mount the mountpoint with pseudo directory, if the autocell
141 * operation is setted.
142 */
143struct inode *afs_try_auto_mntpt(struct dentry *dentry, struct inode *dir)
144{
145 struct afs_vnode *vnode = AFS_FS_I(dir);
146 struct inode *inode;
147 int ret = -ENOENT;
148
149 _enter("%p{%pd}, {%llx:%llu}",
150 dentry, dentry, vnode->fid.vid, vnode->fid.vnode);
151
152 if (!test_bit(AFS_VNODE_AUTOCELL, &vnode->flags))
153 goto out;
154
155 ret = afs_probe_cell_name(dentry);
156 if (ret < 0)
157 goto out;
158
159 inode = afs_iget_pseudo_dir(dir->i_sb, false);
160 if (IS_ERR(inode)) {
161 ret = PTR_ERR(inode);
162 goto out;
163 }
164
165 _leave("= %p", inode);
166 return inode;
167
168out:
169 _leave("= %d", ret);
170 return ret == -ENOENT ? NULL : ERR_PTR(ret);
171}
172
173/*
174 * Look up @cell in a dynroot directory. This is a substitution for the
175 * local cell name for the net namespace.
176 */
177static struct dentry *afs_lookup_atcell(struct dentry *dentry)
178{
179 struct afs_cell *cell;
180 struct afs_net *net = afs_d2net(dentry);
181 struct dentry *ret;
182 unsigned int seq = 0;
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 rcu_read_lock();
195 do {
196 read_seqbegin_or_lock(&net->cells_lock, &seq);
197 cell = rcu_dereference_raw(net->ws_cell);
198 if (cell) {
199 len = cell->name_len;
200 memcpy(name, cell->name, len + 1);
201 }
202 } while (need_seqretry(&net->cells_lock, seq));
203 done_seqretry(&net->cells_lock, seq);
204 rcu_read_unlock();
205
206 ret = ERR_PTR(-ENOENT);
207 if (!cell)
208 goto out_n;
209
210 ret = lookup_one_len(name, dentry->d_parent, len);
211
212 /* We don't want to d_add() the @cell dentry here as we don't want to
213 * the cached dentry to hide changes to the local cell name.
214 */
215
216out_n:
217 kfree(name);
218out_p:
219 return ret;
220}
221
222/*
223 * Look up an entry in a dynroot directory.
224 */
225static struct dentry *afs_dynroot_lookup(struct inode *dir, struct dentry *dentry,
226 unsigned int flags)
227{
228 _enter("%pd", dentry);
229
230 ASSERTCMP(d_inode(dentry), ==, NULL);
231
232 if (flags & LOOKUP_CREATE)
233 return ERR_PTR(-EOPNOTSUPP);
234
235 if (dentry->d_name.len >= AFSNAMEMAX) {
236 _leave(" = -ENAMETOOLONG");
237 return ERR_PTR(-ENAMETOOLONG);
238 }
239
240 if (dentry->d_name.len == 5 &&
241 memcmp(dentry->d_name.name, "@cell", 5) == 0)
242 return afs_lookup_atcell(dentry);
243
244 return d_splice_alias(afs_try_auto_mntpt(dentry, dir), dentry);
245}
246
247const struct inode_operations afs_dynroot_inode_operations = {
248 .lookup = afs_dynroot_lookup,
249};
250
251/*
252 * Dirs in the dynamic root don't need revalidation.
253 */
254static int afs_dynroot_d_revalidate(struct dentry *dentry, unsigned int flags)
255{
256 return 1;
257}
258
259/*
260 * Allow the VFS to enquire as to whether a dentry should be unhashed (mustn't
261 * sleep)
262 * - called from dput() when d_count is going to 0.
263 * - return 1 to request dentry be unhashed, 0 otherwise
264 */
265static int afs_dynroot_d_delete(const struct dentry *dentry)
266{
267 return d_really_is_positive(dentry);
268}
269
270const struct dentry_operations afs_dynroot_dentry_operations = {
271 .d_revalidate = afs_dynroot_d_revalidate,
272 .d_delete = afs_dynroot_d_delete,
273 .d_release = afs_d_release,
274 .d_automount = afs_d_automount,
275};
276
277/*
278 * Create a manually added cell mount directory.
279 * - The caller must hold net->proc_cells_lock
280 */
281int afs_dynroot_mkdir(struct afs_net *net, struct afs_cell *cell)
282{
283 struct super_block *sb = net->dynroot_sb;
284 struct dentry *root, *subdir;
285 int ret;
286
287 if (!sb || atomic_read(&sb->s_active) == 0)
288 return 0;
289
290 /* Let the ->lookup op do the creation */
291 root = sb->s_root;
292 inode_lock(root->d_inode);
293 subdir = lookup_one_len(cell->name, root, cell->name_len);
294 if (IS_ERR(subdir)) {
295 ret = PTR_ERR(subdir);
296 goto unlock;
297 }
298
299 /* Note that we're retaining an extra ref on the dentry */
300 subdir->d_fsdata = (void *)1UL;
301 ret = 0;
302unlock:
303 inode_unlock(root->d_inode);
304 return ret;
305}
306
307/*
308 * Remove a manually added cell mount directory.
309 * - The caller must hold net->proc_cells_lock
310 */
311void afs_dynroot_rmdir(struct afs_net *net, struct afs_cell *cell)
312{
313 struct super_block *sb = net->dynroot_sb;
314 struct dentry *root, *subdir;
315
316 if (!sb || atomic_read(&sb->s_active) == 0)
317 return;
318
319 root = sb->s_root;
320 inode_lock(root->d_inode);
321
322 /* Don't want to trigger a lookup call, which will re-add the cell */
323 subdir = try_lookup_one_len(cell->name, root, cell->name_len);
324 if (IS_ERR_OR_NULL(subdir)) {
325 _debug("lookup %ld", PTR_ERR(subdir));
326 goto no_dentry;
327 }
328
329 _debug("rmdir %pd %u", subdir, d_count(subdir));
330
331 if (subdir->d_fsdata) {
332 _debug("unpin %u", d_count(subdir));
333 subdir->d_fsdata = NULL;
334 dput(subdir);
335 }
336 dput(subdir);
337no_dentry:
338 inode_unlock(root->d_inode);
339 _leave("");
340}
341
342/*
343 * Populate a newly created dynamic root with cell names.
344 */
345int afs_dynroot_populate(struct super_block *sb)
346{
347 struct afs_cell *cell;
348 struct afs_net *net = afs_sb2net(sb);
349 int ret;
350
351 mutex_lock(&net->proc_cells_lock);
352
353 net->dynroot_sb = sb;
354 hlist_for_each_entry(cell, &net->proc_cells, proc_link) {
355 ret = afs_dynroot_mkdir(net, cell);
356 if (ret < 0)
357 goto error;
358 }
359
360 ret = 0;
361out:
362 mutex_unlock(&net->proc_cells_lock);
363 return ret;
364
365error:
366 net->dynroot_sb = NULL;
367 goto out;
368}
369
370/*
371 * When a dynamic root that's in the process of being destroyed, depopulate it
372 * of pinned directories.
373 */
374void afs_dynroot_depopulate(struct super_block *sb)
375{
376 struct afs_net *net = afs_sb2net(sb);
377 struct dentry *root = sb->s_root, *subdir, *tmp;
378
379 /* Prevent more subdirs from being created */
380 mutex_lock(&net->proc_cells_lock);
381 if (net->dynroot_sb == sb)
382 net->dynroot_sb = NULL;
383 mutex_unlock(&net->proc_cells_lock);
384
385 if (root) {
386 inode_lock(root->d_inode);
387
388 /* Remove all the pins for dirs created for manually added cells */
389 list_for_each_entry_safe(subdir, tmp, &root->d_subdirs, d_child) {
390 if (subdir->d_fsdata) {
391 subdir->d_fsdata = NULL;
392 dput(subdir);
393 }
394 }
395
396 inode_unlock(root->d_inode);
397 }
398}