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1/**
2 * \file drm_auth.c
3 * IOCTLs for authentication
4 *
5 * \author Rickard E. (Rik) Faith <faith@valinux.com>
6 * \author Gareth Hughes <gareth@valinux.com>
7 */
8
9/*
10 * Created: Tue Feb 2 08:37:54 1999 by faith@valinux.com
11 *
12 * Copyright 1999 Precision Insight, Inc., Cedar Park, Texas.
13 * Copyright 2000 VA Linux Systems, Inc., Sunnyvale, California.
14 * All Rights Reserved.
15 *
16 * Permission is hereby granted, free of charge, to any person obtaining a
17 * copy of this software and associated documentation files (the "Software"),
18 * to deal in the Software without restriction, including without limitation
19 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
20 * and/or sell copies of the Software, and to permit persons to whom the
21 * Software is furnished to do so, subject to the following conditions:
22 *
23 * The above copyright notice and this permission notice (including the next
24 * paragraph) shall be included in all copies or substantial portions of the
25 * Software.
26 *
27 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
28 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
29 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
30 * VA LINUX SYSTEMS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
31 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
32 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
33 * OTHER DEALINGS IN THE SOFTWARE.
34 */
35
36#include "drmP.h"
37
38/**
39 * Find the file with the given magic number.
40 *
41 * \param dev DRM device.
42 * \param magic magic number.
43 *
44 * Searches in drm_device::magiclist within all files with the same hash key
45 * the one with matching magic number, while holding the drm_device::struct_mutex
46 * lock.
47 */
48static struct drm_file *drm_find_file(struct drm_master *master, drm_magic_t magic)
49{
50 struct drm_file *retval = NULL;
51 struct drm_magic_entry *pt;
52 struct drm_hash_item *hash;
53 struct drm_device *dev = master->minor->dev;
54
55 mutex_lock(&dev->struct_mutex);
56 if (!drm_ht_find_item(&master->magiclist, (unsigned long)magic, &hash)) {
57 pt = drm_hash_entry(hash, struct drm_magic_entry, hash_item);
58 retval = pt->priv;
59 }
60 mutex_unlock(&dev->struct_mutex);
61 return retval;
62}
63
64/**
65 * Adds a magic number.
66 *
67 * \param dev DRM device.
68 * \param priv file private data.
69 * \param magic magic number.
70 *
71 * Creates a drm_magic_entry structure and appends to the linked list
72 * associated the magic number hash key in drm_device::magiclist, while holding
73 * the drm_device::struct_mutex lock.
74 */
75static int drm_add_magic(struct drm_master *master, struct drm_file *priv,
76 drm_magic_t magic)
77{
78 struct drm_magic_entry *entry;
79 struct drm_device *dev = master->minor->dev;
80 DRM_DEBUG("%d\n", magic);
81
82 entry = kzalloc(sizeof(*entry), GFP_KERNEL);
83 if (!entry)
84 return -ENOMEM;
85 entry->priv = priv;
86 entry->hash_item.key = (unsigned long)magic;
87 mutex_lock(&dev->struct_mutex);
88 drm_ht_insert_item(&master->magiclist, &entry->hash_item);
89 list_add_tail(&entry->head, &master->magicfree);
90 mutex_unlock(&dev->struct_mutex);
91
92 return 0;
93}
94
95/**
96 * Remove a magic number.
97 *
98 * \param dev DRM device.
99 * \param magic magic number.
100 *
101 * Searches and unlinks the entry in drm_device::magiclist with the magic
102 * number hash key, while holding the drm_device::struct_mutex lock.
103 */
104static int drm_remove_magic(struct drm_master *master, drm_magic_t magic)
105{
106 struct drm_magic_entry *pt;
107 struct drm_hash_item *hash;
108 struct drm_device *dev = master->minor->dev;
109
110 DRM_DEBUG("%d\n", magic);
111
112 mutex_lock(&dev->struct_mutex);
113 if (drm_ht_find_item(&master->magiclist, (unsigned long)magic, &hash)) {
114 mutex_unlock(&dev->struct_mutex);
115 return -EINVAL;
116 }
117 pt = drm_hash_entry(hash, struct drm_magic_entry, hash_item);
118 drm_ht_remove_item(&master->magiclist, hash);
119 list_del(&pt->head);
120 mutex_unlock(&dev->struct_mutex);
121
122 kfree(pt);
123
124 return 0;
125}
126
127/**
128 * Get a unique magic number (ioctl).
129 *
130 * \param inode device inode.
131 * \param file_priv DRM file private.
132 * \param cmd command.
133 * \param arg pointer to a resulting drm_auth structure.
134 * \return zero on success, or a negative number on failure.
135 *
136 * If there is a magic number in drm_file::magic then use it, otherwise
137 * searches an unique non-zero magic number and add it associating it with \p
138 * file_priv.
139 */
140int drm_getmagic(struct drm_device *dev, void *data, struct drm_file *file_priv)
141{
142 static drm_magic_t sequence = 0;
143 static DEFINE_SPINLOCK(lock);
144 struct drm_auth *auth = data;
145
146 /* Find unique magic */
147 if (file_priv->magic) {
148 auth->magic = file_priv->magic;
149 } else {
150 do {
151 spin_lock(&lock);
152 if (!sequence)
153 ++sequence; /* reserve 0 */
154 auth->magic = sequence++;
155 spin_unlock(&lock);
156 } while (drm_find_file(file_priv->master, auth->magic));
157 file_priv->magic = auth->magic;
158 drm_add_magic(file_priv->master, file_priv, auth->magic);
159 }
160
161 DRM_DEBUG("%u\n", auth->magic);
162
163 return 0;
164}
165
166/**
167 * Authenticate with a magic.
168 *
169 * \param inode device inode.
170 * \param file_priv DRM file private.
171 * \param cmd command.
172 * \param arg pointer to a drm_auth structure.
173 * \return zero if authentication successed, or a negative number otherwise.
174 *
175 * Checks if \p file_priv is associated with the magic number passed in \arg.
176 */
177int drm_authmagic(struct drm_device *dev, void *data,
178 struct drm_file *file_priv)
179{
180 struct drm_auth *auth = data;
181 struct drm_file *file;
182
183 DRM_DEBUG("%u\n", auth->magic);
184 if ((file = drm_find_file(file_priv->master, auth->magic))) {
185 file->authenticated = 1;
186 drm_remove_magic(file_priv->master, auth->magic);
187 return 0;
188 }
189 return -EINVAL;
190}
1/*
2 * Created: Tue Feb 2 08:37:54 1999 by faith@valinux.com
3 *
4 * Copyright 1999 Precision Insight, Inc., Cedar Park, Texas.
5 * Copyright 2000 VA Linux Systems, Inc., Sunnyvale, California.
6 * All Rights Reserved.
7 *
8 * Author Rickard E. (Rik) Faith <faith@valinux.com>
9 * Author Gareth Hughes <gareth@valinux.com>
10 *
11 * Permission is hereby granted, free of charge, to any person obtaining a
12 * copy of this software and associated documentation files (the "Software"),
13 * to deal in the Software without restriction, including without limitation
14 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
15 * and/or sell copies of the Software, and to permit persons to whom the
16 * Software is furnished to do so, subject to the following conditions:
17 *
18 * The above copyright notice and this permission notice (including the next
19 * paragraph) shall be included in all copies or substantial portions of the
20 * Software.
21 *
22 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
23 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
24 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
25 * VA LINUX SYSTEMS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
26 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
27 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
28 * OTHER DEALINGS IN THE SOFTWARE.
29 */
30
31#include <linux/slab.h>
32
33#include <drm/drm_auth.h>
34#include <drm/drm_drv.h>
35#include <drm/drm_file.h>
36#include <drm/drm_lease.h>
37#include <drm/drm_print.h>
38
39#include "drm_internal.h"
40
41/**
42 * DOC: master and authentication
43 *
44 * &struct drm_master is used to track groups of clients with open
45 * primary device nodes. For every &struct drm_file which has had at
46 * least once successfully became the device master (either through the
47 * SET_MASTER IOCTL, or implicitly through opening the primary device node when
48 * no one else is the current master that time) there exists one &drm_master.
49 * This is noted in &drm_file.is_master. All other clients have just a pointer
50 * to the &drm_master they are associated with.
51 *
52 * In addition only one &drm_master can be the current master for a &drm_device.
53 * It can be switched through the DROP_MASTER and SET_MASTER IOCTL, or
54 * implicitly through closing/opening the primary device node. See also
55 * drm_is_current_master().
56 *
57 * Clients can authenticate against the current master (if it matches their own)
58 * using the GETMAGIC and AUTHMAGIC IOCTLs. Together with exchanging masters,
59 * this allows controlled access to the device for an entire group of mutually
60 * trusted clients.
61 */
62
63static bool drm_is_current_master_locked(struct drm_file *fpriv)
64{
65 lockdep_assert_once(lockdep_is_held(&fpriv->master_lookup_lock) ||
66 lockdep_is_held(&fpriv->minor->dev->master_mutex));
67
68 return fpriv->is_master && drm_lease_owner(fpriv->master) == fpriv->minor->dev->master;
69}
70
71/**
72 * drm_is_current_master - checks whether @priv is the current master
73 * @fpriv: DRM file private
74 *
75 * Checks whether @fpriv is current master on its device. This decides whether a
76 * client is allowed to run DRM_MASTER IOCTLs.
77 *
78 * Most of the modern IOCTL which require DRM_MASTER are for kernel modesetting
79 * - the current master is assumed to own the non-shareable display hardware.
80 */
81bool drm_is_current_master(struct drm_file *fpriv)
82{
83 bool ret;
84
85 spin_lock(&fpriv->master_lookup_lock);
86 ret = drm_is_current_master_locked(fpriv);
87 spin_unlock(&fpriv->master_lookup_lock);
88
89 return ret;
90}
91EXPORT_SYMBOL(drm_is_current_master);
92
93int drm_getmagic(struct drm_device *dev, void *data, struct drm_file *file_priv)
94{
95 struct drm_auth *auth = data;
96 int ret = 0;
97
98 mutex_lock(&dev->master_mutex);
99 if (!file_priv->magic) {
100 ret = idr_alloc(&file_priv->master->magic_map, file_priv,
101 1, 0, GFP_KERNEL);
102 if (ret >= 0)
103 file_priv->magic = ret;
104 }
105 auth->magic = file_priv->magic;
106 mutex_unlock(&dev->master_mutex);
107
108 drm_dbg_core(dev, "%u\n", auth->magic);
109
110 return ret < 0 ? ret : 0;
111}
112
113int drm_authmagic(struct drm_device *dev, void *data,
114 struct drm_file *file_priv)
115{
116 struct drm_auth *auth = data;
117 struct drm_file *file;
118
119 drm_dbg_core(dev, "%u\n", auth->magic);
120
121 mutex_lock(&dev->master_mutex);
122 file = idr_find(&file_priv->master->magic_map, auth->magic);
123 if (file) {
124 file->authenticated = 1;
125 idr_replace(&file_priv->master->magic_map, NULL, auth->magic);
126 }
127 mutex_unlock(&dev->master_mutex);
128
129 return file ? 0 : -EINVAL;
130}
131
132struct drm_master *drm_master_create(struct drm_device *dev)
133{
134 struct drm_master *master;
135
136 master = kzalloc(sizeof(*master), GFP_KERNEL);
137 if (!master)
138 return NULL;
139
140 kref_init(&master->refcount);
141 idr_init_base(&master->magic_map, 1);
142 master->dev = dev;
143
144 /* initialize the tree of output resource lessees */
145 INIT_LIST_HEAD(&master->lessees);
146 INIT_LIST_HEAD(&master->lessee_list);
147 idr_init(&master->leases);
148 idr_init_base(&master->lessee_idr, 1);
149
150 return master;
151}
152
153static void drm_set_master(struct drm_device *dev, struct drm_file *fpriv,
154 bool new_master)
155{
156 dev->master = drm_master_get(fpriv->master);
157 if (dev->driver->master_set)
158 dev->driver->master_set(dev, fpriv, new_master);
159
160 fpriv->was_master = true;
161}
162
163static int drm_new_set_master(struct drm_device *dev, struct drm_file *fpriv)
164{
165 struct drm_master *old_master;
166 struct drm_master *new_master;
167
168 lockdep_assert_held_once(&dev->master_mutex);
169
170 WARN_ON(fpriv->is_master);
171 old_master = fpriv->master;
172 new_master = drm_master_create(dev);
173 if (!new_master)
174 return -ENOMEM;
175 spin_lock(&fpriv->master_lookup_lock);
176 fpriv->master = new_master;
177 spin_unlock(&fpriv->master_lookup_lock);
178
179 fpriv->is_master = 1;
180 fpriv->authenticated = 1;
181
182 drm_set_master(dev, fpriv, true);
183
184 if (old_master)
185 drm_master_put(&old_master);
186
187 return 0;
188}
189
190/*
191 * In the olden days the SET/DROP_MASTER ioctls used to return EACCES when
192 * CAP_SYS_ADMIN was not set. This was used to prevent rogue applications
193 * from becoming master and/or failing to release it.
194 *
195 * At the same time, the first client (for a given VT) is _always_ master.
196 * Thus in order for the ioctls to succeed, one had to _explicitly_ run the
197 * application as root or flip the setuid bit.
198 *
199 * If the CAP_SYS_ADMIN was missing, no other client could become master...
200 * EVER :-( Leading to a) the graphics session dying badly or b) a completely
201 * locked session.
202 *
203 *
204 * As some point systemd-logind was introduced to orchestrate and delegate
205 * master as applicable. It does so by opening the fd and passing it to users
206 * while in itself logind a) does the set/drop master per users' request and
207 * b) * implicitly drops master on VT switch.
208 *
209 * Even though logind looks like the future, there are a few issues:
210 * - some platforms don't have equivalent (Android, CrOS, some BSDs) so
211 * root is required _solely_ for SET/DROP MASTER.
212 * - applications may not be updated to use it,
213 * - any client which fails to drop master* can DoS the application using
214 * logind, to a varying degree.
215 *
216 * * Either due missing CAP_SYS_ADMIN or simply not calling DROP_MASTER.
217 *
218 *
219 * Here we implement the next best thing:
220 * - ensure the logind style of fd passing works unchanged, and
221 * - allow a client to drop/set master, iff it is/was master at a given point
222 * in time.
223 *
224 * Note: DROP_MASTER cannot be free for all, as an arbitrator user could:
225 * - DoS/crash the arbitrator - details would be implementation specific
226 * - open the node, become master implicitly and cause issues
227 *
228 * As a result this fixes the following when using root-less build w/o logind
229 * - startx
230 * - weston
231 * - various compositors based on wlroots
232 */
233static int
234drm_master_check_perm(struct drm_device *dev, struct drm_file *file_priv)
235{
236 if (file_priv->was_master &&
237 rcu_access_pointer(file_priv->pid) == task_tgid(current))
238 return 0;
239
240 if (!capable(CAP_SYS_ADMIN))
241 return -EACCES;
242
243 return 0;
244}
245
246int drm_setmaster_ioctl(struct drm_device *dev, void *data,
247 struct drm_file *file_priv)
248{
249 int ret;
250
251 mutex_lock(&dev->master_mutex);
252
253 ret = drm_master_check_perm(dev, file_priv);
254 if (ret)
255 goto out_unlock;
256
257 if (drm_is_current_master_locked(file_priv))
258 goto out_unlock;
259
260 if (dev->master) {
261 ret = -EBUSY;
262 goto out_unlock;
263 }
264
265 if (!file_priv->master) {
266 ret = -EINVAL;
267 goto out_unlock;
268 }
269
270 if (!file_priv->is_master) {
271 ret = drm_new_set_master(dev, file_priv);
272 goto out_unlock;
273 }
274
275 if (file_priv->master->lessor != NULL) {
276 drm_dbg_lease(dev,
277 "Attempt to set lessee %d as master\n",
278 file_priv->master->lessee_id);
279 ret = -EINVAL;
280 goto out_unlock;
281 }
282
283 drm_set_master(dev, file_priv, false);
284out_unlock:
285 mutex_unlock(&dev->master_mutex);
286 return ret;
287}
288
289static void drm_drop_master(struct drm_device *dev,
290 struct drm_file *fpriv)
291{
292 if (dev->driver->master_drop)
293 dev->driver->master_drop(dev, fpriv);
294 drm_master_put(&dev->master);
295}
296
297int drm_dropmaster_ioctl(struct drm_device *dev, void *data,
298 struct drm_file *file_priv)
299{
300 int ret;
301
302 mutex_lock(&dev->master_mutex);
303
304 ret = drm_master_check_perm(dev, file_priv);
305 if (ret)
306 goto out_unlock;
307
308 if (!drm_is_current_master_locked(file_priv)) {
309 ret = -EINVAL;
310 goto out_unlock;
311 }
312
313 if (!dev->master) {
314 ret = -EINVAL;
315 goto out_unlock;
316 }
317
318 if (file_priv->master->lessor != NULL) {
319 drm_dbg_lease(dev,
320 "Attempt to drop lessee %d as master\n",
321 file_priv->master->lessee_id);
322 ret = -EINVAL;
323 goto out_unlock;
324 }
325
326 drm_drop_master(dev, file_priv);
327out_unlock:
328 mutex_unlock(&dev->master_mutex);
329 return ret;
330}
331
332int drm_master_open(struct drm_file *file_priv)
333{
334 struct drm_device *dev = file_priv->minor->dev;
335 int ret = 0;
336
337 /* if there is no current master make this fd it, but do not create
338 * any master object for render clients
339 */
340 mutex_lock(&dev->master_mutex);
341 if (!dev->master) {
342 ret = drm_new_set_master(dev, file_priv);
343 } else {
344 spin_lock(&file_priv->master_lookup_lock);
345 file_priv->master = drm_master_get(dev->master);
346 spin_unlock(&file_priv->master_lookup_lock);
347 }
348 mutex_unlock(&dev->master_mutex);
349
350 return ret;
351}
352
353void drm_master_release(struct drm_file *file_priv)
354{
355 struct drm_device *dev = file_priv->minor->dev;
356 struct drm_master *master;
357
358 mutex_lock(&dev->master_mutex);
359 master = file_priv->master;
360 if (file_priv->magic)
361 idr_remove(&file_priv->master->magic_map, file_priv->magic);
362
363 if (!drm_is_current_master_locked(file_priv))
364 goto out;
365
366 if (dev->master == file_priv->master)
367 drm_drop_master(dev, file_priv);
368out:
369 if (drm_core_check_feature(dev, DRIVER_MODESET) && file_priv->is_master) {
370 /* Revoke any leases held by this or lessees, but only if
371 * this is the "real" master
372 */
373 drm_lease_revoke(master);
374 }
375
376 /* drop the master reference held by the file priv */
377 if (file_priv->master)
378 drm_master_put(&file_priv->master);
379 mutex_unlock(&dev->master_mutex);
380}
381
382/**
383 * drm_master_get - reference a master pointer
384 * @master: &struct drm_master
385 *
386 * Increments the reference count of @master and returns a pointer to @master.
387 */
388struct drm_master *drm_master_get(struct drm_master *master)
389{
390 kref_get(&master->refcount);
391 return master;
392}
393EXPORT_SYMBOL(drm_master_get);
394
395/**
396 * drm_file_get_master - reference &drm_file.master of @file_priv
397 * @file_priv: DRM file private
398 *
399 * Increments the reference count of @file_priv's &drm_file.master and returns
400 * the &drm_file.master. If @file_priv has no &drm_file.master, returns NULL.
401 *
402 * Master pointers returned from this function should be unreferenced using
403 * drm_master_put().
404 */
405struct drm_master *drm_file_get_master(struct drm_file *file_priv)
406{
407 struct drm_master *master = NULL;
408
409 spin_lock(&file_priv->master_lookup_lock);
410 if (!file_priv->master)
411 goto unlock;
412 master = drm_master_get(file_priv->master);
413
414unlock:
415 spin_unlock(&file_priv->master_lookup_lock);
416 return master;
417}
418EXPORT_SYMBOL(drm_file_get_master);
419
420static void drm_master_destroy(struct kref *kref)
421{
422 struct drm_master *master = container_of(kref, struct drm_master, refcount);
423 struct drm_device *dev = master->dev;
424
425 if (drm_core_check_feature(dev, DRIVER_MODESET))
426 drm_lease_destroy(master);
427
428 idr_destroy(&master->magic_map);
429 idr_destroy(&master->leases);
430 idr_destroy(&master->lessee_idr);
431
432 kfree(master->unique);
433 kfree(master);
434}
435
436/**
437 * drm_master_put - unreference and clear a master pointer
438 * @master: pointer to a pointer of &struct drm_master
439 *
440 * This decrements the &drm_master behind @master and sets it to NULL.
441 */
442void drm_master_put(struct drm_master **master)
443{
444 kref_put(&(*master)->refcount, drm_master_destroy);
445 *master = NULL;
446}
447EXPORT_SYMBOL(drm_master_put);
448
449/* Used by drm_client and drm_fb_helper */
450bool drm_master_internal_acquire(struct drm_device *dev)
451{
452 mutex_lock(&dev->master_mutex);
453 if (dev->master) {
454 mutex_unlock(&dev->master_mutex);
455 return false;
456 }
457
458 return true;
459}
460EXPORT_SYMBOL(drm_master_internal_acquire);
461
462/* Used by drm_client and drm_fb_helper */
463void drm_master_internal_release(struct drm_device *dev)
464{
465 mutex_unlock(&dev->master_mutex);
466}
467EXPORT_SYMBOL(drm_master_internal_release);