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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);
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 inode->i_ctime = inode->i_atime = inode->i_mtime = current_time(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 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 */
144struct 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
169out:
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 */
178static 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
212out_n:
213 kfree(name);
214out_p:
215 return ret;
216}
217
218/*
219 * Look up an entry in a dynroot directory.
220 */
221static 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
243const 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 */
250static 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 */
261static int afs_dynroot_d_delete(const struct dentry *dentry)
262{
263 return d_really_is_positive(dentry);
264}
265
266const 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 */
277int 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;
298unlock:
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 */
307void 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);
333no_dentry:
334 inode_unlock(root->d_inode);
335 _leave("");
336}
337
338/*
339 * Populate a newly created dynamic root with cell names.
340 */
341int 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;
357out:
358 mutex_unlock(&net->proc_cells_lock);
359 return ret;
360
361error:
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 */
370void 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}