1 /* AFS cell and server record management
2  *
3  * Copyright (C) 2002 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 License
8  * as published by the Free Software Foundation; either version
9  * 2 of the License, or (at your option) any later version.
10  */
11 
12 #include <linux/module.h>
13 #include <linux/slab.h>
14 #include <linux/key.h>
15 #include <linux/ctype.h>
16 #include <linux/dns_resolver.h>
17 #include <linux/sched.h>
18 #include <keys/rxrpc-type.h>
19 #include "internal.h"
20 
21 DECLARE_RWSEM(afs_proc_cells_sem);
22 LIST_HEAD(afs_proc_cells);
23 
24 static LIST_HEAD(afs_cells);
25 static DEFINE_RWLOCK(afs_cells_lock);
26 static DECLARE_RWSEM(afs_cells_sem); /* add/remove serialisation */
27 static DECLARE_WAIT_QUEUE_HEAD(afs_cells_freeable_wq);
28 static struct afs_cell *afs_cell_root;
29 
30 /*
31  * allocate a cell record and fill in its name, VL server address list and
32  * allocate an anonymous key
33  */
afs_cell_alloc(const char * name,unsigned namelen,char * vllist)34 static struct afs_cell *afs_cell_alloc(const char *name, unsigned namelen,
35 				       char *vllist)
36 {
37 	struct afs_cell *cell;
38 	struct key *key;
39 	char keyname[4 + AFS_MAXCELLNAME + 1], *cp, *dp, *next;
40 	char  *dvllist = NULL, *_vllist = NULL;
41 	char  delimiter = ':';
42 	int ret;
43 
44 	_enter("%*.*s,%s", namelen, namelen, name ?: "", vllist);
45 
46 	BUG_ON(!name); /* TODO: want to look up "this cell" in the cache */
47 
48 	if (namelen > AFS_MAXCELLNAME) {
49 		_leave(" = -ENAMETOOLONG");
50 		return ERR_PTR(-ENAMETOOLONG);
51 	}
52 
53 	/* allocate and initialise a cell record */
54 	cell = kzalloc(sizeof(struct afs_cell) + namelen + 1, GFP_KERNEL);
55 	if (!cell) {
56 		_leave(" = -ENOMEM");
57 		return ERR_PTR(-ENOMEM);
58 	}
59 
60 	memcpy(cell->name, name, namelen);
61 	cell->name[namelen] = 0;
62 
63 	atomic_set(&cell->usage, 1);
64 	INIT_LIST_HEAD(&cell->link);
65 	rwlock_init(&cell->servers_lock);
66 	INIT_LIST_HEAD(&cell->servers);
67 	init_rwsem(&cell->vl_sem);
68 	INIT_LIST_HEAD(&cell->vl_list);
69 	spin_lock_init(&cell->vl_lock);
70 
71 	/* if the ip address is invalid, try dns query */
72 	if (!vllist || strlen(vllist) < 7) {
73 		ret = dns_query("afsdb", name, namelen, "ipv4", &dvllist, NULL);
74 		if (ret < 0) {
75 			if (ret == -ENODATA || ret == -EAGAIN || ret == -ENOKEY)
76 				/* translate these errors into something
77 				 * userspace might understand */
78 				ret = -EDESTADDRREQ;
79 			_leave(" = %d", ret);
80 			return ERR_PTR(ret);
81 		}
82 		_vllist = dvllist;
83 
84 		/* change the delimiter for user-space reply */
85 		delimiter = ',';
86 
87 	} else {
88 		_vllist = vllist;
89 	}
90 
91 	/* fill in the VL server list from the rest of the string */
92 	do {
93 		unsigned a, b, c, d;
94 
95 		next = strchr(_vllist, delimiter);
96 		if (next)
97 			*next++ = 0;
98 
99 		if (sscanf(_vllist, "%u.%u.%u.%u", &a, &b, &c, &d) != 4)
100 			goto bad_address;
101 
102 		if (a > 255 || b > 255 || c > 255 || d > 255)
103 			goto bad_address;
104 
105 		cell->vl_addrs[cell->vl_naddrs++].s_addr =
106 			htonl((a << 24) | (b << 16) | (c << 8) | d);
107 
108 	} while (cell->vl_naddrs < AFS_CELL_MAX_ADDRS && (_vllist = next));
109 
110 	/* create a key to represent an anonymous user */
111 	memcpy(keyname, "afs@", 4);
112 	dp = keyname + 4;
113 	cp = cell->name;
114 	do {
115 		*dp++ = toupper(*cp);
116 	} while (*cp++);
117 
118 	key = rxrpc_get_null_key(keyname);
119 	if (IS_ERR(key)) {
120 		_debug("no key");
121 		ret = PTR_ERR(key);
122 		goto error;
123 	}
124 	cell->anonymous_key = key;
125 
126 	_debug("anon key %p{%x}",
127 	       cell->anonymous_key, key_serial(cell->anonymous_key));
128 
129 	_leave(" = %p", cell);
130 	return cell;
131 
132 bad_address:
133 	printk(KERN_ERR "kAFS: bad VL server IP address\n");
134 	ret = -EINVAL;
135 error:
136 	key_put(cell->anonymous_key);
137 	kfree(dvllist);
138 	kfree(cell);
139 	_leave(" = %d", ret);
140 	return ERR_PTR(ret);
141 }
142 
143 /*
144  * afs_cell_crate() - create a cell record
145  * @name:	is the name of the cell.
146  * @namsesz:	is the strlen of the cell name.
147  * @vllist:	is a colon separated list of IP addresses in "a.b.c.d" format.
148  * @retref:	is T to return the cell reference when the cell exists.
149  */
afs_cell_create(const char * name,unsigned namesz,char * vllist,bool retref)150 struct afs_cell *afs_cell_create(const char *name, unsigned namesz,
151 				 char *vllist, bool retref)
152 {
153 	struct afs_cell *cell;
154 	int ret;
155 
156 	_enter("%*.*s,%s", namesz, namesz, name ?: "", vllist);
157 
158 	down_write(&afs_cells_sem);
159 	read_lock(&afs_cells_lock);
160 	list_for_each_entry(cell, &afs_cells, link) {
161 		if (strncasecmp(cell->name, name, namesz) == 0)
162 			goto duplicate_name;
163 	}
164 	read_unlock(&afs_cells_lock);
165 
166 	cell = afs_cell_alloc(name, namesz, vllist);
167 	if (IS_ERR(cell)) {
168 		_leave(" = %ld", PTR_ERR(cell));
169 		up_write(&afs_cells_sem);
170 		return cell;
171 	}
172 
173 	/* add a proc directory for this cell */
174 	ret = afs_proc_cell_setup(cell);
175 	if (ret < 0)
176 		goto error;
177 
178 #ifdef CONFIG_AFS_FSCACHE
179 	/* put it up for caching (this never returns an error) */
180 	cell->cache = fscache_acquire_cookie(afs_cache_netfs.primary_index,
181 					     &afs_cell_cache_index_def,
182 					     cell);
183 #endif
184 
185 	/* add to the cell lists */
186 	write_lock(&afs_cells_lock);
187 	list_add_tail(&cell->link, &afs_cells);
188 	write_unlock(&afs_cells_lock);
189 
190 	down_write(&afs_proc_cells_sem);
191 	list_add_tail(&cell->proc_link, &afs_proc_cells);
192 	up_write(&afs_proc_cells_sem);
193 	up_write(&afs_cells_sem);
194 
195 	_leave(" = %p", cell);
196 	return cell;
197 
198 error:
199 	up_write(&afs_cells_sem);
200 	key_put(cell->anonymous_key);
201 	kfree(cell);
202 	_leave(" = %d", ret);
203 	return ERR_PTR(ret);
204 
205 duplicate_name:
206 	if (retref && !IS_ERR(cell))
207 		afs_get_cell(cell);
208 
209 	read_unlock(&afs_cells_lock);
210 	up_write(&afs_cells_sem);
211 
212 	if (retref) {
213 		_leave(" = %p", cell);
214 		return cell;
215 	}
216 
217 	_leave(" = -EEXIST");
218 	return ERR_PTR(-EEXIST);
219 }
220 
221 /*
222  * set the root cell information
223  * - can be called with a module parameter string
224  * - can be called from a write to /proc/fs/afs/rootcell
225  */
afs_cell_init(char * rootcell)226 int afs_cell_init(char *rootcell)
227 {
228 	struct afs_cell *old_root, *new_root;
229 	char *cp;
230 
231 	_enter("");
232 
233 	if (!rootcell) {
234 		/* module is loaded with no parameters, or built statically.
235 		 * - in the future we might initialize cell DB here.
236 		 */
237 		_leave(" = 0 [no root]");
238 		return 0;
239 	}
240 
241 	cp = strchr(rootcell, ':');
242 	if (!cp)
243 		_debug("kAFS: no VL server IP addresses specified");
244 	else
245 		*cp++ = 0;
246 
247 	/* allocate a cell record for the root cell */
248 	new_root = afs_cell_create(rootcell, strlen(rootcell), cp, false);
249 	if (IS_ERR(new_root)) {
250 		_leave(" = %ld", PTR_ERR(new_root));
251 		return PTR_ERR(new_root);
252 	}
253 
254 	/* install the new cell */
255 	write_lock(&afs_cells_lock);
256 	old_root = afs_cell_root;
257 	afs_cell_root = new_root;
258 	write_unlock(&afs_cells_lock);
259 	afs_put_cell(old_root);
260 
261 	_leave(" = 0");
262 	return 0;
263 }
264 
265 /*
266  * lookup a cell record
267  */
afs_cell_lookup(const char * name,unsigned namesz,bool dns_cell)268 struct afs_cell *afs_cell_lookup(const char *name, unsigned namesz,
269 				 bool dns_cell)
270 {
271 	struct afs_cell *cell;
272 
273 	_enter("\"%*.*s\",", namesz, namesz, name ?: "");
274 
275 	down_read(&afs_cells_sem);
276 	read_lock(&afs_cells_lock);
277 
278 	if (name) {
279 		/* if the cell was named, look for it in the cell record list */
280 		list_for_each_entry(cell, &afs_cells, link) {
281 			if (strncmp(cell->name, name, namesz) == 0) {
282 				afs_get_cell(cell);
283 				goto found;
284 			}
285 		}
286 		cell = ERR_PTR(-ENOENT);
287 		if (dns_cell)
288 			goto create_cell;
289 	found:
290 		;
291 	} else {
292 		cell = afs_cell_root;
293 		if (!cell) {
294 			/* this should not happen unless user tries to mount
295 			 * when root cell is not set. Return an impossibly
296 			 * bizarre errno to alert the user. Things like
297 			 * ENOENT might be "more appropriate" but they happen
298 			 * for other reasons.
299 			 */
300 			cell = ERR_PTR(-EDESTADDRREQ);
301 		} else {
302 			afs_get_cell(cell);
303 		}
304 
305 	}
306 
307 	read_unlock(&afs_cells_lock);
308 	up_read(&afs_cells_sem);
309 	_leave(" = %p", cell);
310 	return cell;
311 
312 create_cell:
313 	read_unlock(&afs_cells_lock);
314 	up_read(&afs_cells_sem);
315 
316 	cell = afs_cell_create(name, namesz, NULL, true);
317 
318 	_leave(" = %p", cell);
319 	return cell;
320 }
321 
322 #if 0
323 /*
324  * try and get a cell record
325  */
326 struct afs_cell *afs_get_cell_maybe(struct afs_cell *cell)
327 {
328 	write_lock(&afs_cells_lock);
329 
330 	if (cell && !list_empty(&cell->link))
331 		afs_get_cell(cell);
332 	else
333 		cell = NULL;
334 
335 	write_unlock(&afs_cells_lock);
336 	return cell;
337 }
338 #endif  /*  0  */
339 
340 /*
341  * destroy a cell record
342  */
afs_put_cell(struct afs_cell * cell)343 void afs_put_cell(struct afs_cell *cell)
344 {
345 	if (!cell)
346 		return;
347 
348 	_enter("%p{%d,%s}", cell, atomic_read(&cell->usage), cell->name);
349 
350 	ASSERTCMP(atomic_read(&cell->usage), >, 0);
351 
352 	/* to prevent a race, the decrement and the dequeue must be effectively
353 	 * atomic */
354 	write_lock(&afs_cells_lock);
355 
356 	if (likely(!atomic_dec_and_test(&cell->usage))) {
357 		write_unlock(&afs_cells_lock);
358 		_leave("");
359 		return;
360 	}
361 
362 	ASSERT(list_empty(&cell->servers));
363 	ASSERT(list_empty(&cell->vl_list));
364 
365 	write_unlock(&afs_cells_lock);
366 
367 	wake_up(&afs_cells_freeable_wq);
368 
369 	_leave(" [unused]");
370 }
371 
372 /*
373  * destroy a cell record
374  * - must be called with the afs_cells_sem write-locked
375  * - cell->link should have been broken by the caller
376  */
afs_cell_destroy(struct afs_cell * cell)377 static void afs_cell_destroy(struct afs_cell *cell)
378 {
379 	_enter("%p{%d,%s}", cell, atomic_read(&cell->usage), cell->name);
380 
381 	ASSERTCMP(atomic_read(&cell->usage), >=, 0);
382 	ASSERT(list_empty(&cell->link));
383 
384 	/* wait for everyone to stop using the cell */
385 	if (atomic_read(&cell->usage) > 0) {
386 		DECLARE_WAITQUEUE(myself, current);
387 
388 		_debug("wait for cell %s", cell->name);
389 		set_current_state(TASK_UNINTERRUPTIBLE);
390 		add_wait_queue(&afs_cells_freeable_wq, &myself);
391 
392 		while (atomic_read(&cell->usage) > 0) {
393 			schedule();
394 			set_current_state(TASK_UNINTERRUPTIBLE);
395 		}
396 
397 		remove_wait_queue(&afs_cells_freeable_wq, &myself);
398 		set_current_state(TASK_RUNNING);
399 	}
400 
401 	_debug("cell dead");
402 	ASSERTCMP(atomic_read(&cell->usage), ==, 0);
403 	ASSERT(list_empty(&cell->servers));
404 	ASSERT(list_empty(&cell->vl_list));
405 
406 	afs_proc_cell_remove(cell);
407 
408 	down_write(&afs_proc_cells_sem);
409 	list_del_init(&cell->proc_link);
410 	up_write(&afs_proc_cells_sem);
411 
412 #ifdef CONFIG_AFS_FSCACHE
413 	fscache_relinquish_cookie(cell->cache, 0);
414 #endif
415 	key_put(cell->anonymous_key);
416 	kfree(cell);
417 
418 	_leave(" [destroyed]");
419 }
420 
421 /*
422  * purge in-memory cell database on module unload or afs_init() failure
423  * - the timeout daemon is stopped before calling this
424  */
afs_cell_purge(void)425 void afs_cell_purge(void)
426 {
427 	struct afs_cell *cell;
428 
429 	_enter("");
430 
431 	afs_put_cell(afs_cell_root);
432 
433 	down_write(&afs_cells_sem);
434 
435 	while (!list_empty(&afs_cells)) {
436 		cell = NULL;
437 
438 		/* remove the next cell from the front of the list */
439 		write_lock(&afs_cells_lock);
440 
441 		if (!list_empty(&afs_cells)) {
442 			cell = list_entry(afs_cells.next,
443 					  struct afs_cell, link);
444 			list_del_init(&cell->link);
445 		}
446 
447 		write_unlock(&afs_cells_lock);
448 
449 		if (cell) {
450 			_debug("PURGING CELL %s (%d)",
451 			       cell->name, atomic_read(&cell->usage));
452 
453 			/* now the cell should be left with no references */
454 			afs_cell_destroy(cell);
455 		}
456 	}
457 
458 	up_write(&afs_cells_sem);
459 	_leave("");
460 }
461