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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 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 */
111static 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 */
158struct 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
183out:
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 */
192static 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
226out_n:
227 kfree(name);
228out_p:
229 return ret;
230}
231
232/*
233 * Look up an entry in a dynroot directory.
234 */
235static 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
257const struct inode_operations afs_dynroot_inode_operations = {
258 .lookup = afs_dynroot_lookup,
259};
260
261const 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 */
271int 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;
292unlock:
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 */
301void 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);
327no_dentry:
328 inode_unlock(root->d_inode);
329 _leave("");
330}
331
332/*
333 * Populate a newly created dynamic root with cell names.
334 */
335int 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;
351out:
352 mutex_unlock(&net->proc_cells_lock);
353 return ret;
354
355error:
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 */
364void 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}