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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}
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/*
14 * Probe to see if a cell may exist. This prevents positive dentries from
15 * being created unnecessarily.
16 */
17static int afs_probe_cell_name(struct dentry *dentry)
18{
19 struct afs_cell *cell;
20 struct afs_net *net = afs_d2net(dentry);
21 const char *name = dentry->d_name.name;
22 size_t len = dentry->d_name.len;
23 int ret;
24
25 /* Names prefixed with a dot are R/W mounts. */
26 if (name[0] == '.') {
27 if (len == 1)
28 return -EINVAL;
29 name++;
30 len--;
31 }
32
33 cell = afs_lookup_cell_rcu(net, name, len);
34 if (!IS_ERR(cell)) {
35 afs_put_cell(net, cell);
36 return 0;
37 }
38
39 ret = dns_query(net->net, "afsdb", name, len, "srv=1",
40 NULL, NULL, false);
41 if (ret == -ENODATA)
42 ret = -EDESTADDRREQ;
43 return ret;
44}
45
46/*
47 * Try to auto mount the mountpoint with pseudo directory, if the autocell
48 * operation is setted.
49 */
50struct inode *afs_try_auto_mntpt(struct dentry *dentry, struct inode *dir)
51{
52 struct afs_vnode *vnode = AFS_FS_I(dir);
53 struct inode *inode;
54 int ret = -ENOENT;
55
56 _enter("%p{%pd}, {%llx:%llu}",
57 dentry, dentry, vnode->fid.vid, vnode->fid.vnode);
58
59 if (!test_bit(AFS_VNODE_AUTOCELL, &vnode->flags))
60 goto out;
61
62 ret = afs_probe_cell_name(dentry);
63 if (ret < 0)
64 goto out;
65
66 inode = afs_iget_pseudo_dir(dir->i_sb, false);
67 if (IS_ERR(inode)) {
68 ret = PTR_ERR(inode);
69 goto out;
70 }
71
72 _leave("= %p", inode);
73 return inode;
74
75out:
76 _leave("= %d", ret);
77 return ret == -ENOENT ? NULL : ERR_PTR(ret);
78}
79
80/*
81 * Look up @cell in a dynroot directory. This is a substitution for the
82 * local cell name for the net namespace.
83 */
84static struct dentry *afs_lookup_atcell(struct dentry *dentry)
85{
86 struct afs_cell *cell;
87 struct afs_net *net = afs_d2net(dentry);
88 struct dentry *ret;
89 unsigned int seq = 0;
90 char *name;
91 int len;
92
93 if (!net->ws_cell)
94 return ERR_PTR(-ENOENT);
95
96 ret = ERR_PTR(-ENOMEM);
97 name = kmalloc(AFS_MAXCELLNAME + 1, GFP_KERNEL);
98 if (!name)
99 goto out_p;
100
101 rcu_read_lock();
102 do {
103 read_seqbegin_or_lock(&net->cells_lock, &seq);
104 cell = rcu_dereference_raw(net->ws_cell);
105 if (cell) {
106 len = cell->name_len;
107 memcpy(name, cell->name, len + 1);
108 }
109 } while (need_seqretry(&net->cells_lock, seq));
110 done_seqretry(&net->cells_lock, seq);
111 rcu_read_unlock();
112
113 ret = ERR_PTR(-ENOENT);
114 if (!cell)
115 goto out_n;
116
117 ret = lookup_one_len(name, dentry->d_parent, len);
118
119 /* We don't want to d_add() the @cell dentry here as we don't want to
120 * the cached dentry to hide changes to the local cell name.
121 */
122
123out_n:
124 kfree(name);
125out_p:
126 return ret;
127}
128
129/*
130 * Look up an entry in a dynroot directory.
131 */
132static struct dentry *afs_dynroot_lookup(struct inode *dir, struct dentry *dentry,
133 unsigned int flags)
134{
135 _enter("%pd", dentry);
136
137 ASSERTCMP(d_inode(dentry), ==, NULL);
138
139 if (dentry->d_name.len >= AFSNAMEMAX) {
140 _leave(" = -ENAMETOOLONG");
141 return ERR_PTR(-ENAMETOOLONG);
142 }
143
144 if (dentry->d_name.len == 5 &&
145 memcmp(dentry->d_name.name, "@cell", 5) == 0)
146 return afs_lookup_atcell(dentry);
147
148 return d_splice_alias(afs_try_auto_mntpt(dentry, dir), dentry);
149}
150
151const struct inode_operations afs_dynroot_inode_operations = {
152 .lookup = afs_dynroot_lookup,
153};
154
155/*
156 * Dirs in the dynamic root don't need revalidation.
157 */
158static int afs_dynroot_d_revalidate(struct dentry *dentry, unsigned int flags)
159{
160 return 1;
161}
162
163/*
164 * Allow the VFS to enquire as to whether a dentry should be unhashed (mustn't
165 * sleep)
166 * - called from dput() when d_count is going to 0.
167 * - return 1 to request dentry be unhashed, 0 otherwise
168 */
169static int afs_dynroot_d_delete(const struct dentry *dentry)
170{
171 return d_really_is_positive(dentry);
172}
173
174const struct dentry_operations afs_dynroot_dentry_operations = {
175 .d_revalidate = afs_dynroot_d_revalidate,
176 .d_delete = afs_dynroot_d_delete,
177 .d_release = afs_d_release,
178 .d_automount = afs_d_automount,
179};
180
181/*
182 * Create a manually added cell mount directory.
183 * - The caller must hold net->proc_cells_lock
184 */
185int afs_dynroot_mkdir(struct afs_net *net, struct afs_cell *cell)
186{
187 struct super_block *sb = net->dynroot_sb;
188 struct dentry *root, *subdir;
189 int ret;
190
191 if (!sb || atomic_read(&sb->s_active) == 0)
192 return 0;
193
194 /* Let the ->lookup op do the creation */
195 root = sb->s_root;
196 inode_lock(root->d_inode);
197 subdir = lookup_one_len(cell->name, root, cell->name_len);
198 if (IS_ERR(subdir)) {
199 ret = PTR_ERR(subdir);
200 goto unlock;
201 }
202
203 /* Note that we're retaining an extra ref on the dentry */
204 subdir->d_fsdata = (void *)1UL;
205 ret = 0;
206unlock:
207 inode_unlock(root->d_inode);
208 return ret;
209}
210
211/*
212 * Remove a manually added cell mount directory.
213 * - The caller must hold net->proc_cells_lock
214 */
215void afs_dynroot_rmdir(struct afs_net *net, struct afs_cell *cell)
216{
217 struct super_block *sb = net->dynroot_sb;
218 struct dentry *root, *subdir;
219
220 if (!sb || atomic_read(&sb->s_active) == 0)
221 return;
222
223 root = sb->s_root;
224 inode_lock(root->d_inode);
225
226 /* Don't want to trigger a lookup call, which will re-add the cell */
227 subdir = try_lookup_one_len(cell->name, root, cell->name_len);
228 if (IS_ERR_OR_NULL(subdir)) {
229 _debug("lookup %ld", PTR_ERR(subdir));
230 goto no_dentry;
231 }
232
233 _debug("rmdir %pd %u", subdir, d_count(subdir));
234
235 if (subdir->d_fsdata) {
236 _debug("unpin %u", d_count(subdir));
237 subdir->d_fsdata = NULL;
238 dput(subdir);
239 }
240 dput(subdir);
241no_dentry:
242 inode_unlock(root->d_inode);
243 _leave("");
244}
245
246/*
247 * Populate a newly created dynamic root with cell names.
248 */
249int afs_dynroot_populate(struct super_block *sb)
250{
251 struct afs_cell *cell;
252 struct afs_net *net = afs_sb2net(sb);
253 int ret;
254
255 mutex_lock(&net->proc_cells_lock);
256
257 net->dynroot_sb = sb;
258 hlist_for_each_entry(cell, &net->proc_cells, proc_link) {
259 ret = afs_dynroot_mkdir(net, cell);
260 if (ret < 0)
261 goto error;
262 }
263
264 ret = 0;
265out:
266 mutex_unlock(&net->proc_cells_lock);
267 return ret;
268
269error:
270 net->dynroot_sb = NULL;
271 goto out;
272}
273
274/*
275 * When a dynamic root that's in the process of being destroyed, depopulate it
276 * of pinned directories.
277 */
278void afs_dynroot_depopulate(struct super_block *sb)
279{
280 struct afs_net *net = afs_sb2net(sb);
281 struct dentry *root = sb->s_root, *subdir, *tmp;
282
283 /* Prevent more subdirs from being created */
284 mutex_lock(&net->proc_cells_lock);
285 if (net->dynroot_sb == sb)
286 net->dynroot_sb = NULL;
287 mutex_unlock(&net->proc_cells_lock);
288
289 inode_lock(root->d_inode);
290
291 /* Remove all the pins for dirs created for manually added cells */
292 list_for_each_entry_safe(subdir, tmp, &root->d_subdirs, d_child) {
293 if (subdir->d_fsdata) {
294 subdir->d_fsdata = NULL;
295 dput(subdir);
296 }
297 }
298
299 inode_unlock(root->d_inode);
300}