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b4d0d230 | 1 | // SPDX-License-Identifier: GPL-2.0-or-later |
0da0b7fd | 2 | /* AFS dynamic root handling |
66c7e1d3 DH |
3 | * |
4 | * Copyright (C) 2018 Red Hat, Inc. All Rights Reserved. | |
5 | * Written by David Howells (dhowells@redhat.com) | |
66c7e1d3 DH |
6 | */ |
7 | ||
8 | #include <linux/fs.h> | |
9 | #include <linux/namei.h> | |
10 | #include <linux/dns_resolver.h> | |
11 | #include "internal.h" | |
12 | ||
66c7e1d3 DH |
13 | /* |
14 | * Probe to see if a cell may exist. This prevents positive dentries from | |
15 | * being created unnecessarily. | |
16 | */ | |
17 | static int afs_probe_cell_name(struct dentry *dentry) | |
18 | { | |
19 | struct afs_cell *cell; | |
a58946c1 | 20 | struct afs_net *net = afs_d2net(dentry); |
66c7e1d3 DH |
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 | ||
a58946c1 | 33 | cell = afs_lookup_cell_rcu(net, name, len); |
66c7e1d3 | 34 | if (!IS_ERR(cell)) { |
a58946c1 | 35 | afs_put_cell(net, cell); |
66c7e1d3 DH |
36 | return 0; |
37 | } | |
38 | ||
a58946c1 DH |
39 | ret = dns_query(net->net, "afsdb", name, len, "srv=1", |
40 | NULL, NULL, false); | |
66c7e1d3 DH |
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 | */ | |
50 | struct 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 | ||
3b6492df | 56 | _enter("%p{%pd}, {%llx:%llu}", |
66c7e1d3 DH |
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 | ||
75 | out: | |
76 | _leave("= %d", ret); | |
1401a0fc | 77 | return ret == -ENOENT ? NULL : ERR_PTR(ret); |
66c7e1d3 DH |
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 | */ | |
84 | static 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 | ||
123 | out_n: | |
124 | kfree(name); | |
125 | out_p: | |
126 | return ret; | |
127 | } | |
128 | ||
129 | /* | |
130 | * Look up an entry in a dynroot directory. | |
131 | */ | |
132 | static struct dentry *afs_dynroot_lookup(struct inode *dir, struct dentry *dentry, | |
133 | unsigned int flags) | |
134 | { | |
66c7e1d3 DH |
135 | _enter("%pd", dentry); |
136 | ||
137 | ASSERTCMP(d_inode(dentry), ==, NULL); | |
138 | ||
1da4bd9f DH |
139 | if (flags & LOOKUP_CREATE) |
140 | return ERR_PTR(-EOPNOTSUPP); | |
141 | ||
66c7e1d3 DH |
142 | if (dentry->d_name.len >= AFSNAMEMAX) { |
143 | _leave(" = -ENAMETOOLONG"); | |
144 | return ERR_PTR(-ENAMETOOLONG); | |
145 | } | |
146 | ||
147 | if (dentry->d_name.len == 5 && | |
148 | memcmp(dentry->d_name.name, "@cell", 5) == 0) | |
149 | return afs_lookup_atcell(dentry); | |
150 | ||
1401a0fc | 151 | return d_splice_alias(afs_try_auto_mntpt(dentry, dir), dentry); |
66c7e1d3 DH |
152 | } |
153 | ||
154 | const struct inode_operations afs_dynroot_inode_operations = { | |
155 | .lookup = afs_dynroot_lookup, | |
156 | }; | |
157 | ||
158 | /* | |
159 | * Dirs in the dynamic root don't need revalidation. | |
160 | */ | |
161 | static int afs_dynroot_d_revalidate(struct dentry *dentry, unsigned int flags) | |
162 | { | |
163 | return 1; | |
164 | } | |
165 | ||
166 | /* | |
167 | * Allow the VFS to enquire as to whether a dentry should be unhashed (mustn't | |
168 | * sleep) | |
169 | * - called from dput() when d_count is going to 0. | |
170 | * - return 1 to request dentry be unhashed, 0 otherwise | |
171 | */ | |
172 | static int afs_dynroot_d_delete(const struct dentry *dentry) | |
173 | { | |
174 | return d_really_is_positive(dentry); | |
175 | } | |
176 | ||
177 | const struct dentry_operations afs_dynroot_dentry_operations = { | |
178 | .d_revalidate = afs_dynroot_d_revalidate, | |
179 | .d_delete = afs_dynroot_d_delete, | |
180 | .d_release = afs_d_release, | |
181 | .d_automount = afs_d_automount, | |
182 | }; | |
0da0b7fd DH |
183 | |
184 | /* | |
185 | * Create a manually added cell mount directory. | |
186 | * - The caller must hold net->proc_cells_lock | |
187 | */ | |
188 | int afs_dynroot_mkdir(struct afs_net *net, struct afs_cell *cell) | |
189 | { | |
190 | struct super_block *sb = net->dynroot_sb; | |
191 | struct dentry *root, *subdir; | |
192 | int ret; | |
193 | ||
194 | if (!sb || atomic_read(&sb->s_active) == 0) | |
195 | return 0; | |
196 | ||
197 | /* Let the ->lookup op do the creation */ | |
198 | root = sb->s_root; | |
199 | inode_lock(root->d_inode); | |
200 | subdir = lookup_one_len(cell->name, root, cell->name_len); | |
201 | if (IS_ERR(subdir)) { | |
202 | ret = PTR_ERR(subdir); | |
203 | goto unlock; | |
204 | } | |
205 | ||
206 | /* Note that we're retaining an extra ref on the dentry */ | |
207 | subdir->d_fsdata = (void *)1UL; | |
208 | ret = 0; | |
209 | unlock: | |
210 | inode_unlock(root->d_inode); | |
211 | return ret; | |
212 | } | |
213 | ||
214 | /* | |
215 | * Remove a manually added cell mount directory. | |
216 | * - The caller must hold net->proc_cells_lock | |
217 | */ | |
218 | void afs_dynroot_rmdir(struct afs_net *net, struct afs_cell *cell) | |
219 | { | |
220 | struct super_block *sb = net->dynroot_sb; | |
221 | struct dentry *root, *subdir; | |
222 | ||
223 | if (!sb || atomic_read(&sb->s_active) == 0) | |
224 | return; | |
225 | ||
226 | root = sb->s_root; | |
227 | inode_lock(root->d_inode); | |
228 | ||
229 | /* Don't want to trigger a lookup call, which will re-add the cell */ | |
230 | subdir = try_lookup_one_len(cell->name, root, cell->name_len); | |
231 | if (IS_ERR_OR_NULL(subdir)) { | |
232 | _debug("lookup %ld", PTR_ERR(subdir)); | |
233 | goto no_dentry; | |
234 | } | |
235 | ||
236 | _debug("rmdir %pd %u", subdir, d_count(subdir)); | |
237 | ||
238 | if (subdir->d_fsdata) { | |
239 | _debug("unpin %u", d_count(subdir)); | |
240 | subdir->d_fsdata = NULL; | |
241 | dput(subdir); | |
242 | } | |
243 | dput(subdir); | |
244 | no_dentry: | |
245 | inode_unlock(root->d_inode); | |
246 | _leave(""); | |
247 | } | |
248 | ||
249 | /* | |
250 | * Populate a newly created dynamic root with cell names. | |
251 | */ | |
252 | int afs_dynroot_populate(struct super_block *sb) | |
253 | { | |
254 | struct afs_cell *cell; | |
255 | struct afs_net *net = afs_sb2net(sb); | |
256 | int ret; | |
257 | ||
3b05e528 | 258 | mutex_lock(&net->proc_cells_lock); |
0da0b7fd DH |
259 | |
260 | net->dynroot_sb = sb; | |
6b3944e4 | 261 | hlist_for_each_entry(cell, &net->proc_cells, proc_link) { |
0da0b7fd DH |
262 | ret = afs_dynroot_mkdir(net, cell); |
263 | if (ret < 0) | |
264 | goto error; | |
265 | } | |
266 | ||
267 | ret = 0; | |
268 | out: | |
269 | mutex_unlock(&net->proc_cells_lock); | |
270 | return ret; | |
271 | ||
272 | error: | |
273 | net->dynroot_sb = NULL; | |
274 | goto out; | |
275 | } | |
276 | ||
277 | /* | |
278 | * When a dynamic root that's in the process of being destroyed, depopulate it | |
279 | * of pinned directories. | |
280 | */ | |
281 | void afs_dynroot_depopulate(struct super_block *sb) | |
282 | { | |
283 | struct afs_net *net = afs_sb2net(sb); | |
284 | struct dentry *root = sb->s_root, *subdir, *tmp; | |
285 | ||
286 | /* Prevent more subdirs from being created */ | |
287 | mutex_lock(&net->proc_cells_lock); | |
288 | if (net->dynroot_sb == sb) | |
289 | net->dynroot_sb = NULL; | |
290 | mutex_unlock(&net->proc_cells_lock); | |
291 | ||
292 | inode_lock(root->d_inode); | |
293 | ||
294 | /* Remove all the pins for dirs created for manually added cells */ | |
295 | list_for_each_entry_safe(subdir, tmp, &root->d_subdirs, d_child) { | |
296 | if (subdir->d_fsdata) { | |
297 | subdir->d_fsdata = NULL; | |
298 | dput(subdir); | |
299 | } | |
300 | } | |
301 | ||
302 | inode_unlock(root->d_inode); | |
303 | } |