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 | static 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 | */ |
20 | static int afs_iget5_pseudo_test(struct inode *inode, void *opaque) |
21 | { |
22 | return 0; |
23 | } |
24 | |
25 | /* |
26 | * iget5() inode initialiser |
27 | */ |
28 | static int afs_iget5_pseudo_set(struct inode *inode, void *opaque) |
29 | { |
30 | struct afs_super_info *as = AFS_FS_S(sb: 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 | */ |
45 | struct 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(v: &afs_autocell_ino); |
61 | fid.unique = 0; |
62 | } |
63 | |
64 | inode = iget5_locked(sb, fid.vnode, |
65 | test: afs_iget5_pseudo_test, set: afs_iget5_pseudo_set, &fid); |
66 | if (!inode) { |
67 | _leave(" = -ENOMEM" ); |
68 | return ERR_PTR(error: -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(ctx: &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, nlink: 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 | */ |
111 | static 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(ptr: cell)) { |
129 | afs_unuse_cell(net, cell, afs_cell_trace_unuse_probe); |
130 | return 0; |
131 | } |
132 | |
133 | ret = dns_query(net: net->net, type: "afsdb" , name, namelen: len, options: "srv=1" , |
134 | NULL, NULL, invalidate: 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 | */ |
144 | struct inode *afs_try_auto_mntpt(struct dentry *dentry, struct inode *dir) |
145 | { |
146 | struct afs_vnode *vnode = AFS_FS_I(inode: 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(sb: dir->i_sb, root: false); |
161 | if (IS_ERR(ptr: inode)) { |
162 | ret = PTR_ERR(ptr: inode); |
163 | goto out; |
164 | } |
165 | |
166 | _leave("= %p" , inode); |
167 | return inode; |
168 | |
169 | out: |
170 | _leave("= %d" , ret); |
171 | return ret == -ENOENT ? NULL : ERR_PTR(error: 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 | */ |
178 | static 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(error: -ENOENT); |
188 | |
189 | ret = ERR_PTR(error: -ENOMEM); |
190 | name = kmalloc(AFS_MAXCELLNAME + 1, GFP_KERNEL); |
191 | if (!name) |
192 | goto out_p; |
193 | |
194 | down_read(sem: &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(sem: &net->cells_lock); |
201 | |
202 | ret = ERR_PTR(error: -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 | |
212 | out_n: |
213 | kfree(objp: name); |
214 | out_p: |
215 | return ret; |
216 | } |
217 | |
218 | /* |
219 | * Look up an entry in a dynroot directory. |
220 | */ |
221 | static 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(error: -EOPNOTSUPP); |
230 | |
231 | if (dentry->d_name.len >= AFSNAMEMAX) { |
232 | _leave(" = -ENAMETOOLONG" ); |
233 | return ERR_PTR(error: -ENAMETOOLONG); |
234 | } |
235 | |
236 | if (dentry->d_name.len == 5 && |
237 | memcmp(p: dentry->d_name.name, q: "@cell" , size: 5) == 0) |
238 | return afs_lookup_atcell(dentry); |
239 | |
240 | return d_splice_alias(afs_try_auto_mntpt(dentry, dir), dentry); |
241 | } |
242 | |
243 | const 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 | */ |
250 | static 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 | */ |
261 | static int afs_dynroot_d_delete(const struct dentry *dentry) |
262 | { |
263 | return d_really_is_positive(dentry); |
264 | } |
265 | |
266 | const 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 | */ |
277 | int 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(v: &sb->s_active) == 0) |
284 | return 0; |
285 | |
286 | /* Let the ->lookup op do the creation */ |
287 | root = sb->s_root; |
288 | inode_lock(inode: root->d_inode); |
289 | subdir = lookup_one_len(cell->name, root, cell->name_len); |
290 | if (IS_ERR(ptr: subdir)) { |
291 | ret = PTR_ERR(ptr: 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; |
298 | unlock: |
299 | inode_unlock(inode: 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 | */ |
307 | void 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(v: &sb->s_active) == 0) |
313 | return; |
314 | |
315 | root = sb->s_root; |
316 | inode_lock(inode: 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(ptr: 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); |
333 | no_dentry: |
334 | inode_unlock(inode: root->d_inode); |
335 | _leave("" ); |
336 | } |
337 | |
338 | /* |
339 | * Populate a newly created dynamic root with cell names. |
340 | */ |
341 | int 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; |
357 | out: |
358 | mutex_unlock(lock: &net->proc_cells_lock); |
359 | return ret; |
360 | |
361 | error: |
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 | */ |
370 | void 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(lock: &net->proc_cells_lock); |
380 | |
381 | if (root) { |
382 | inode_lock(inode: 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(inode: root->d_inode); |
393 | } |
394 | } |
395 | |