• Home
  • Line#
  • Scopes#
  • Navigate#
  • Raw
  • Download
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  */
afs_iget5_pseudo_test(struct inode * inode,void * opaque)20 static int afs_iget5_pseudo_test(struct inode *inode, void *opaque)
21 {
22 	return 0;
23 }
24 
25 /*
26  * iget5() inode initialiser
27  */
afs_iget5_pseudo_set(struct inode * inode,void * opaque)28 static 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  */
afs_iget_pseudo_dir(struct super_block * sb,bool root)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(&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 	inode->i_size		= 0;
80 	inode->i_mode		= S_IFDIR | S_IRUGO | S_IXUGO;
81 	if (root) {
82 		inode->i_op	= &afs_dynroot_inode_operations;
83 		inode->i_fop	= &simple_dir_operations;
84 	} else {
85 		inode->i_op	= &afs_autocell_inode_operations;
86 	}
87 	set_nlink(inode, 2);
88 	inode->i_uid		= GLOBAL_ROOT_UID;
89 	inode->i_gid		= GLOBAL_ROOT_GID;
90 	inode->i_ctime = inode->i_atime = inode->i_mtime = current_time(inode);
91 	inode->i_blocks		= 0;
92 	inode->i_generation	= 0;
93 
94 	set_bit(AFS_VNODE_PSEUDODIR, &vnode->flags);
95 	if (!root) {
96 		set_bit(AFS_VNODE_MOUNTPOINT, &vnode->flags);
97 		inode->i_flags |= S_AUTOMOUNT;
98 	}
99 
100 	inode->i_flags |= S_NOATIME;
101 	unlock_new_inode(inode);
102 	_leave(" = %p", inode);
103 	return inode;
104 }
105 
106 /*
107  * Probe to see if a cell may exist.  This prevents positive dentries from
108  * being created unnecessarily.
109  */
afs_probe_cell_name(struct dentry * dentry)110 static int afs_probe_cell_name(struct dentry *dentry)
111 {
112 	struct afs_cell *cell;
113 	struct afs_net *net = afs_d2net(dentry);
114 	const char *name = dentry->d_name.name;
115 	size_t len = dentry->d_name.len;
116 	char *result = NULL;
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 			&result, NULL, false);
135 	if (ret == -ENODATA || ret == -ENOKEY || ret == 0)
136 		ret = -ENOENT;
137 	if (ret > 0 && ret >= sizeof(struct dns_server_list_v1_header)) {
138 		struct dns_server_list_v1_header *v1 = (void *)result;
139 
140 		if (v1->hdr.zero == 0 &&
141 		    v1->hdr.content == DNS_PAYLOAD_IS_SERVER_LIST &&
142 		    v1->hdr.version == 1 &&
143 		    (v1->status != DNS_LOOKUP_GOOD &&
144 		     v1->status != DNS_LOOKUP_GOOD_WITH_BAD))
145 			return -ENOENT;
146 
147 	}
148 
149 	kfree(result);
150 	return ret;
151 }
152 
153 /*
154  * Try to auto mount the mountpoint with pseudo directory, if the autocell
155  * operation is setted.
156  */
afs_try_auto_mntpt(struct dentry * dentry,struct inode * dir)157 struct inode *afs_try_auto_mntpt(struct dentry *dentry, struct inode *dir)
158 {
159 	struct afs_vnode *vnode = AFS_FS_I(dir);
160 	struct inode *inode;
161 	int ret = -ENOENT;
162 
163 	_enter("%p{%pd}, {%llx:%llu}",
164 	       dentry, dentry, vnode->fid.vid, vnode->fid.vnode);
165 
166 	if (!test_bit(AFS_VNODE_AUTOCELL, &vnode->flags))
167 		goto out;
168 
169 	ret = afs_probe_cell_name(dentry);
170 	if (ret < 0)
171 		goto out;
172 
173 	inode = afs_iget_pseudo_dir(dir->i_sb, false);
174 	if (IS_ERR(inode)) {
175 		ret = PTR_ERR(inode);
176 		goto out;
177 	}
178 
179 	_leave("= %p", inode);
180 	return inode;
181 
182 out:
183 	_leave("= %d", ret);
184 	return ret == -ENOENT ? NULL : ERR_PTR(ret);
185 }
186 
187 /*
188  * Look up @cell in a dynroot directory.  This is a substitution for the
189  * local cell name for the net namespace.
190  */
afs_lookup_atcell(struct dentry * dentry)191 static struct dentry *afs_lookup_atcell(struct dentry *dentry)
192 {
193 	struct afs_cell *cell;
194 	struct afs_net *net = afs_d2net(dentry);
195 	struct dentry *ret;
196 	char *name;
197 	int len;
198 
199 	if (!net->ws_cell)
200 		return ERR_PTR(-ENOENT);
201 
202 	ret = ERR_PTR(-ENOMEM);
203 	name = kmalloc(AFS_MAXCELLNAME + 1, GFP_KERNEL);
204 	if (!name)
205 		goto out_p;
206 
207 	down_read(&net->cells_lock);
208 	cell = net->ws_cell;
209 	if (cell) {
210 		len = cell->name_len;
211 		memcpy(name, cell->name, len + 1);
212 	}
213 	up_read(&net->cells_lock);
214 
215 	ret = ERR_PTR(-ENOENT);
216 	if (!cell)
217 		goto out_n;
218 
219 	ret = lookup_one_len(name, dentry->d_parent, len);
220 
221 	/* We don't want to d_add() the @cell dentry here as we don't want to
222 	 * the cached dentry to hide changes to the local cell name.
223 	 */
224 
225 out_n:
226 	kfree(name);
227 out_p:
228 	return ret;
229 }
230 
231 /*
232  * Look up an entry in a dynroot directory.
233  */
afs_dynroot_lookup(struct inode * dir,struct dentry * dentry,unsigned int flags)234 static struct dentry *afs_dynroot_lookup(struct inode *dir, struct dentry *dentry,
235 					 unsigned int flags)
236 {
237 	_enter("%pd", dentry);
238 
239 	ASSERTCMP(d_inode(dentry), ==, NULL);
240 
241 	if (flags & LOOKUP_CREATE)
242 		return ERR_PTR(-EOPNOTSUPP);
243 
244 	if (dentry->d_name.len >= AFSNAMEMAX) {
245 		_leave(" = -ENAMETOOLONG");
246 		return ERR_PTR(-ENAMETOOLONG);
247 	}
248 
249 	if (dentry->d_name.len == 5 &&
250 	    memcmp(dentry->d_name.name, "@cell", 5) == 0)
251 		return afs_lookup_atcell(dentry);
252 
253 	return d_splice_alias(afs_try_auto_mntpt(dentry, dir), dentry);
254 }
255 
256 const struct inode_operations afs_dynroot_inode_operations = {
257 	.lookup		= afs_dynroot_lookup,
258 };
259 
260 /*
261  * Dirs in the dynamic root don't need revalidation.
262  */
afs_dynroot_d_revalidate(struct dentry * dentry,unsigned int flags)263 static int afs_dynroot_d_revalidate(struct dentry *dentry, unsigned int flags)
264 {
265 	return 1;
266 }
267 
268 const struct dentry_operations afs_dynroot_dentry_operations = {
269 	.d_revalidate	= afs_dynroot_d_revalidate,
270 	.d_delete	= always_delete_dentry,
271 	.d_release	= afs_d_release,
272 	.d_automount	= afs_d_automount,
273 };
274 
275 /*
276  * Create a manually added cell mount directory.
277  * - The caller must hold net->proc_cells_lock
278  */
afs_dynroot_mkdir(struct afs_net * net,struct afs_cell * cell)279 int afs_dynroot_mkdir(struct afs_net *net, struct afs_cell *cell)
280 {
281 	struct super_block *sb = net->dynroot_sb;
282 	struct dentry *root, *subdir;
283 	int ret;
284 
285 	if (!sb || atomic_read(&sb->s_active) == 0)
286 		return 0;
287 
288 	/* Let the ->lookup op do the creation */
289 	root = sb->s_root;
290 	inode_lock(root->d_inode);
291 	subdir = lookup_one_len(cell->name, root, cell->name_len);
292 	if (IS_ERR(subdir)) {
293 		ret = PTR_ERR(subdir);
294 		goto unlock;
295 	}
296 
297 	/* Note that we're retaining an extra ref on the dentry */
298 	subdir->d_fsdata = (void *)1UL;
299 	ret = 0;
300 unlock:
301 	inode_unlock(root->d_inode);
302 	return ret;
303 }
304 
305 /*
306  * Remove a manually added cell mount directory.
307  * - The caller must hold net->proc_cells_lock
308  */
afs_dynroot_rmdir(struct afs_net * net,struct afs_cell * cell)309 void afs_dynroot_rmdir(struct afs_net *net, struct afs_cell *cell)
310 {
311 	struct super_block *sb = net->dynroot_sb;
312 	struct dentry *root, *subdir;
313 
314 	if (!sb || atomic_read(&sb->s_active) == 0)
315 		return;
316 
317 	root = sb->s_root;
318 	inode_lock(root->d_inode);
319 
320 	/* Don't want to trigger a lookup call, which will re-add the cell */
321 	subdir = try_lookup_one_len(cell->name, root, cell->name_len);
322 	if (IS_ERR_OR_NULL(subdir)) {
323 		_debug("lookup %ld", PTR_ERR(subdir));
324 		goto no_dentry;
325 	}
326 
327 	_debug("rmdir %pd %u", subdir, d_count(subdir));
328 
329 	if (subdir->d_fsdata) {
330 		_debug("unpin %u", d_count(subdir));
331 		subdir->d_fsdata = NULL;
332 		dput(subdir);
333 	}
334 	dput(subdir);
335 no_dentry:
336 	inode_unlock(root->d_inode);
337 	_leave("");
338 }
339 
340 /*
341  * Populate a newly created dynamic root with cell names.
342  */
afs_dynroot_populate(struct super_block * sb)343 int afs_dynroot_populate(struct super_block *sb)
344 {
345 	struct afs_cell *cell;
346 	struct afs_net *net = afs_sb2net(sb);
347 	int ret;
348 
349 	mutex_lock(&net->proc_cells_lock);
350 
351 	net->dynroot_sb = sb;
352 	hlist_for_each_entry(cell, &net->proc_cells, proc_link) {
353 		ret = afs_dynroot_mkdir(net, cell);
354 		if (ret < 0)
355 			goto error;
356 	}
357 
358 	ret = 0;
359 out:
360 	mutex_unlock(&net->proc_cells_lock);
361 	return ret;
362 
363 error:
364 	net->dynroot_sb = NULL;
365 	goto out;
366 }
367 
368 /*
369  * When a dynamic root that's in the process of being destroyed, depopulate it
370  * of pinned directories.
371  */
afs_dynroot_depopulate(struct super_block * sb)372 void afs_dynroot_depopulate(struct super_block *sb)
373 {
374 	struct afs_net *net = afs_sb2net(sb);
375 	struct dentry *root = sb->s_root, *subdir, *tmp;
376 
377 	/* Prevent more subdirs from being created */
378 	mutex_lock(&net->proc_cells_lock);
379 	if (net->dynroot_sb == sb)
380 		net->dynroot_sb = NULL;
381 	mutex_unlock(&net->proc_cells_lock);
382 
383 	if (root) {
384 		inode_lock(root->d_inode);
385 
386 		/* Remove all the pins for dirs created for manually added cells */
387 		list_for_each_entry_safe(subdir, tmp, &root->d_subdirs, d_child) {
388 			if (subdir->d_fsdata) {
389 				subdir->d_fsdata = NULL;
390 				dput(subdir);
391 			}
392 		}
393 
394 		inode_unlock(root->d_inode);
395 	}
396 }
397