1 /* AFS security handling
3 * Copyright (C) 2007, 2017 Red Hat, Inc. All Rights Reserved.
4 * Written by David Howells (dhowells@redhat.com)
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.
12 #include <linux/init.h>
13 #include <linux/slab.h>
15 #include <linux/ctype.h>
16 #include <linux/sched.h>
17 #include <linux/hashtable.h>
18 #include <keys/rxrpc-type.h>
21 static DEFINE_HASHTABLE(afs_permits_cache, 10);
22 static DEFINE_SPINLOCK(afs_permits_lock);
27 struct key *afs_request_key(struct afs_cell *cell)
31 _enter("{%x}", key_serial(cell->anonymous_key));
33 _debug("key %s", cell->anonymous_key->description);
34 key = request_key(&key_type_rxrpc, cell->anonymous_key->description,
37 if (PTR_ERR(key) != -ENOKEY) {
38 _leave(" = %ld", PTR_ERR(key));
42 /* act as anonymous user */
43 _leave(" = {%x} [anon]", key_serial(cell->anonymous_key));
44 return key_get(cell->anonymous_key);
46 /* act as authorised user */
47 _leave(" = {%x} [auth]", key_serial(key));
53 * Dispose of a list of permits.
55 static void afs_permits_rcu(struct rcu_head *rcu)
57 struct afs_permits *permits =
58 container_of(rcu, struct afs_permits, rcu);
61 for (i = 0; i < permits->nr_permits; i++)
62 key_put(permits->permits[i].key);
67 * Discard a permission cache.
69 void afs_put_permits(struct afs_permits *permits)
71 if (permits && refcount_dec_and_test(&permits->usage)) {
72 spin_lock(&afs_permits_lock);
73 hash_del_rcu(&permits->hash_node);
74 spin_unlock(&afs_permits_lock);
75 call_rcu(&permits->rcu, afs_permits_rcu);
80 * Clear a permit cache on callback break.
82 void afs_clear_permits(struct afs_vnode *vnode)
84 struct afs_permits *permits;
86 spin_lock(&vnode->lock);
87 permits = rcu_dereference_protected(vnode->permit_cache,
88 lockdep_is_held(&vnode->lock));
89 RCU_INIT_POINTER(vnode->permit_cache, NULL);
91 spin_unlock(&vnode->lock);
94 afs_put_permits(permits);
98 * Hash a list of permits. Use simple addition to make it easy to add an extra
99 * one at an as-yet indeterminate position in the list.
101 static void afs_hash_permits(struct afs_permits *permits)
103 unsigned long h = permits->nr_permits;
106 for (i = 0; i < permits->nr_permits; i++) {
107 h += (unsigned long)permits->permits[i].key / sizeof(void *);
108 h += permits->permits[i].access;
115 * Cache the CallerAccess result obtained from doing a fileserver operation
116 * that returned a vnode status for a particular key. If a callback break
117 * occurs whilst the operation was in progress then we have to ditch the cache
118 * as the ACL *may* have changed.
120 void afs_cache_permit(struct afs_vnode *vnode, struct key *key,
121 unsigned int cb_break)
123 struct afs_permits *permits, *xpermits, *replacement, *new = NULL;
124 afs_access_t caller_access = READ_ONCE(vnode->status.caller_access);
126 bool changed = false;
129 _enter("{%x:%u},%x,%x",
130 vnode->fid.vid, vnode->fid.vnode, key_serial(key), caller_access);
134 /* Check for the common case first: We got back the same access as last
135 * time we tried and already have it recorded.
137 permits = rcu_dereference(vnode->permit_cache);
139 if (!permits->invalidated) {
140 for (i = 0; i < permits->nr_permits; i++) {
141 if (permits->permits[i].key < key)
143 if (permits->permits[i].key > key)
145 if (permits->permits[i].access != caller_access) {
150 if (cb_break != (vnode->cb_break +
151 vnode->cb_interest->server->cb_s_break)) {
156 /* The cache is still good. */
162 changed |= permits->invalidated;
163 size = permits->nr_permits;
165 /* If this set of permits is now wrong, clear the permits
166 * pointer so that no one tries to use the stale information.
169 spin_lock(&vnode->lock);
170 if (permits != rcu_access_pointer(vnode->permit_cache))
171 goto someone_else_changed_it_unlock;
172 RCU_INIT_POINTER(vnode->permit_cache, NULL);
173 spin_unlock(&vnode->lock);
175 afs_put_permits(permits);
181 if (cb_break != (vnode->cb_break + vnode->cb_interest->server->cb_s_break)) {
183 goto someone_else_changed_it;
186 /* We need a ref on any permits list we want to copy as we'll have to
187 * drop the lock to do memory allocation.
189 if (permits && !refcount_inc_not_zero(&permits->usage)) {
191 goto someone_else_changed_it;
196 /* Speculatively create a new list with the revised permission set. We
197 * discard this if we find an extant match already in the hash, but
198 * it's easier to compare with memcmp this way.
200 * We fill in the key pointers at this time, but we don't get the refs
204 new = kzalloc(sizeof(struct afs_permits) +
205 sizeof(struct afs_permit) * size, GFP_NOFS);
209 refcount_set(&new->usage, 1);
210 new->nr_permits = size;
213 for (i = 0; i < permits->nr_permits; i++) {
214 if (j == i && permits->permits[i].key > key) {
215 new->permits[j].key = key;
216 new->permits[j].access = caller_access;
219 new->permits[j].key = permits->permits[i].key;
220 new->permits[j].access = permits->permits[i].access;
226 new->permits[j].key = key;
227 new->permits[j].access = caller_access;
230 afs_hash_permits(new);
232 afs_put_permits(permits);
234 /* Now see if the permit list we want is actually already available */
235 spin_lock(&afs_permits_lock);
237 hash_for_each_possible(afs_permits_cache, xpermits, hash_node, new->h) {
238 if (xpermits->h != new->h ||
239 xpermits->invalidated ||
240 xpermits->nr_permits != new->nr_permits ||
241 memcmp(xpermits->permits, new->permits,
242 new->nr_permits * sizeof(struct afs_permit)) != 0)
245 if (refcount_inc_not_zero(&xpermits->usage)) {
246 replacement = xpermits;
253 for (i = 0; i < new->nr_permits; i++)
254 key_get(new->permits[i].key);
255 hash_add_rcu(afs_permits_cache, &new->hash_node, new->h);
260 spin_unlock(&afs_permits_lock);
264 spin_lock(&vnode->lock);
265 if (cb_break != (vnode->cb_break + vnode->cb_interest->server->cb_s_break) ||
266 permits != rcu_access_pointer(vnode->permit_cache))
267 goto someone_else_changed_it_unlock;
268 rcu_assign_pointer(vnode->permit_cache, replacement);
269 spin_unlock(&vnode->lock);
270 afs_put_permits(permits);
273 someone_else_changed_it_unlock:
274 spin_unlock(&vnode->lock);
275 someone_else_changed_it:
276 /* Someone else changed the cache under us - don't recheck at this
283 * check with the fileserver to see if the directory or parent directory is
284 * permitted to be accessed with this authorisation, and if so, what access it
287 int afs_check_permit(struct afs_vnode *vnode, struct key *key,
288 afs_access_t *_access)
290 struct afs_permits *permits;
295 vnode->fid.vid, vnode->fid.vnode, key_serial(key));
297 permits = vnode->permit_cache;
299 /* check the permits to see if we've got one yet */
300 if (key == vnode->volume->cell->anonymous_key) {
302 *_access = vnode->status.anon_access;
306 permits = rcu_dereference(vnode->permit_cache);
308 for (i = 0; i < permits->nr_permits; i++) {
309 if (permits->permits[i].key < key)
311 if (permits->permits[i].key > key)
314 *_access = permits->permits[i].access;
315 valid = !permits->invalidated;
323 /* Check the status on the file we're actually interested in
324 * (the post-processing will cache the result).
326 _debug("no valid permit");
328 ret = afs_fetch_status(vnode, key);
331 _leave(" = %d", ret);
334 *_access = vnode->status.caller_access;
337 _leave(" = 0 [access %x]", *_access);
342 * check the permissions on an AFS file
343 * - AFS ACLs are attached to directories only, and a file is controlled by its
344 * parent directory's ACL
346 int afs_permission(struct inode *inode, int mask)
348 struct afs_vnode *vnode = AFS_FS_I(inode);
349 afs_access_t uninitialized_var(access);
353 if (mask & MAY_NOT_BLOCK)
356 _enter("{{%x:%u},%lx},%x,",
357 vnode->fid.vid, vnode->fid.vnode, vnode->flags, mask);
359 key = afs_request_key(vnode->volume->cell);
361 _leave(" = %ld [key]", PTR_ERR(key));
365 ret = afs_validate(vnode, key);
369 /* check the permits to see if we've got one yet */
370 ret = afs_check_permit(vnode, key, &access);
374 /* interpret the access mask */
375 _debug("REQ %x ACC %x on %s",
376 mask, access, S_ISDIR(inode->i_mode) ? "dir" : "file");
378 if (S_ISDIR(inode->i_mode)) {
379 if (mask & MAY_EXEC) {
380 if (!(access & AFS_ACE_LOOKUP))
381 goto permission_denied;
382 } else if (mask & MAY_READ) {
383 if (!(access & AFS_ACE_LOOKUP))
384 goto permission_denied;
385 } else if (mask & MAY_WRITE) {
386 if (!(access & (AFS_ACE_DELETE | /* rmdir, unlink, rename from */
387 AFS_ACE_INSERT))) /* create, mkdir, symlink, rename to */
388 goto permission_denied;
393 if (!(access & AFS_ACE_LOOKUP))
394 goto permission_denied;
395 if ((mask & MAY_EXEC) && !(inode->i_mode & S_IXUSR))
396 goto permission_denied;
397 if (mask & (MAY_EXEC | MAY_READ)) {
398 if (!(access & AFS_ACE_READ))
399 goto permission_denied;
400 if (!(inode->i_mode & S_IRUSR))
401 goto permission_denied;
402 } else if (mask & MAY_WRITE) {
403 if (!(access & AFS_ACE_WRITE))
404 goto permission_denied;
405 if (!(inode->i_mode & S_IWUSR))
406 goto permission_denied;
411 _leave(" = %d", ret);
418 _leave(" = %d", ret);
422 void __exit afs_clean_up_permit_cache(void)
426 for (i = 0; i < HASH_SIZE(afs_permits_cache); i++)
427 WARN_ON_ONCE(!hlist_empty(&afs_permits_cache[i]));