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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
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}