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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#include "drm_legacy.h"
41
42/**
43 * DOC: master and authentication
44 *
45 * &struct drm_master is used to track groups of clients with open
46 * primary/legacy device nodes. For every &struct drm_file which has had at
47 * least once successfully became the device master (either through the
48 * SET_MASTER IOCTL, or implicitly through opening the primary device node when
49 * no one else is the current master that time) there exists one &drm_master.
50 * This is noted in &drm_file.is_master. All other clients have just a pointer
51 * to the &drm_master they are associated with.
52 *
53 * In addition only one &drm_master can be the current master for a &drm_device.
54 * It can be switched through the DROP_MASTER and SET_MASTER IOCTL, or
55 * implicitly through closing/opening the primary device node. See also
56 * drm_is_current_master().
57 *
58 * Clients can authenticate against the current master (if it matches their own)
59 * using the GETMAGIC and AUTHMAGIC IOCTLs. Together with exchanging masters,
60 * this allows controlled access to the device for an entire group of mutually
61 * trusted clients.
62 */
63
64static bool drm_is_current_master_locked(struct drm_file *fpriv)
65{
66 lockdep_assert_once(lockdep_is_held(&fpriv->master_lookup_lock) ||
67 lockdep_is_held(&fpriv->minor->dev->master_mutex));
68
69 return fpriv->is_master && drm_lease_owner(fpriv->master) == fpriv->minor->dev->master;
70}
71
72/**
73 * drm_is_current_master - checks whether @priv is the current master
74 * @fpriv: DRM file private
75 *
76 * Checks whether @fpriv is current master on its device. This decides whether a
77 * client is allowed to run DRM_MASTER IOCTLs.
78 *
79 * Most of the modern IOCTL which require DRM_MASTER are for kernel modesetting
80 * - the current master is assumed to own the non-shareable display hardware.
81 */
82bool drm_is_current_master(struct drm_file *fpriv)
83{
84 bool ret;
85
86 spin_lock(&fpriv->master_lookup_lock);
87 ret = drm_is_current_master_locked(fpriv);
88 spin_unlock(&fpriv->master_lookup_lock);
89
90 return ret;
91}
92EXPORT_SYMBOL(drm_is_current_master);
93
94int drm_getmagic(struct drm_device *dev, void *data, struct drm_file *file_priv)
95{
96 struct drm_auth *auth = data;
97 int ret = 0;
98
99 mutex_lock(&dev->master_mutex);
100 if (!file_priv->magic) {
101 ret = idr_alloc(&file_priv->master->magic_map, file_priv,
102 1, 0, GFP_KERNEL);
103 if (ret >= 0)
104 file_priv->magic = ret;
105 }
106 auth->magic = file_priv->magic;
107 mutex_unlock(&dev->master_mutex);
108
109 drm_dbg_core(dev, "%u\n", auth->magic);
110
111 return ret < 0 ? ret : 0;
112}
113
114int drm_authmagic(struct drm_device *dev, void *data,
115 struct drm_file *file_priv)
116{
117 struct drm_auth *auth = data;
118 struct drm_file *file;
119
120 drm_dbg_core(dev, "%u\n", auth->magic);
121
122 mutex_lock(&dev->master_mutex);
123 file = idr_find(&file_priv->master->magic_map, auth->magic);
124 if (file) {
125 file->authenticated = 1;
126 idr_replace(&file_priv->master->magic_map, NULL, auth->magic);
127 }
128 mutex_unlock(&dev->master_mutex);
129
130 return file ? 0 : -EINVAL;
131}
132
133struct drm_master *drm_master_create(struct drm_device *dev)
134{
135 struct drm_master *master;
136
137 master = kzalloc(sizeof(*master), GFP_KERNEL);
138 if (!master)
139 return NULL;
140
141 kref_init(&master->refcount);
142 drm_master_legacy_init(master);
143 idr_init_base(&master->magic_map, 1);
144 master->dev = dev;
145
146 /* initialize the tree of output resource lessees */
147 INIT_LIST_HEAD(&master->lessees);
148 INIT_LIST_HEAD(&master->lessee_list);
149 idr_init(&master->leases);
150 idr_init_base(&master->lessee_idr, 1);
151
152 return master;
153}
154
155static void drm_set_master(struct drm_device *dev, struct drm_file *fpriv,
156 bool new_master)
157{
158 dev->master = drm_master_get(fpriv->master);
159 if (dev->driver->master_set)
160 dev->driver->master_set(dev, fpriv, new_master);
161
162 fpriv->was_master = true;
163}
164
165static int drm_new_set_master(struct drm_device *dev, struct drm_file *fpriv)
166{
167 struct drm_master *old_master;
168 struct drm_master *new_master;
169
170 lockdep_assert_held_once(&dev->master_mutex);
171
172 WARN_ON(fpriv->is_master);
173 old_master = fpriv->master;
174 new_master = drm_master_create(dev);
175 if (!new_master)
176 return -ENOMEM;
177 spin_lock(&fpriv->master_lookup_lock);
178 fpriv->master = new_master;
179 spin_unlock(&fpriv->master_lookup_lock);
180
181 fpriv->is_master = 1;
182 fpriv->authenticated = 1;
183
184 drm_set_master(dev, fpriv, true);
185
186 if (old_master)
187 drm_master_put(&old_master);
188
189 return 0;
190}
191
192/*
193 * In the olden days the SET/DROP_MASTER ioctls used to return EACCES when
194 * CAP_SYS_ADMIN was not set. This was used to prevent rogue applications
195 * from becoming master and/or failing to release it.
196 *
197 * At the same time, the first client (for a given VT) is _always_ master.
198 * Thus in order for the ioctls to succeed, one had to _explicitly_ run the
199 * application as root or flip the setuid bit.
200 *
201 * If the CAP_SYS_ADMIN was missing, no other client could become master...
202 * EVER :-( Leading to a) the graphics session dying badly or b) a completely
203 * locked session.
204 *
205 *
206 * As some point systemd-logind was introduced to orchestrate and delegate
207 * master as applicable. It does so by opening the fd and passing it to users
208 * while in itself logind a) does the set/drop master per users' request and
209 * b) * implicitly drops master on VT switch.
210 *
211 * Even though logind looks like the future, there are a few issues:
212 * - some platforms don't have equivalent (Android, CrOS, some BSDs) so
213 * root is required _solely_ for SET/DROP MASTER.
214 * - applications may not be updated to use it,
215 * - any client which fails to drop master* can DoS the application using
216 * logind, to a varying degree.
217 *
218 * * Either due missing CAP_SYS_ADMIN or simply not calling DROP_MASTER.
219 *
220 *
221 * Here we implement the next best thing:
222 * - ensure the logind style of fd passing works unchanged, and
223 * - allow a client to drop/set master, iff it is/was master at a given point
224 * in time.
225 *
226 * Note: DROP_MASTER cannot be free for all, as an arbitrator user could:
227 * - DoS/crash the arbitrator - details would be implementation specific
228 * - open the node, become master implicitly and cause issues
229 *
230 * As a result this fixes the following when using root-less build w/o logind
231 * - startx
232 * - weston
233 * - various compositors based on wlroots
234 */
235static int
236drm_master_check_perm(struct drm_device *dev, struct drm_file *file_priv)
237{
238 if (file_priv->pid == task_pid(current) && file_priv->was_master)
239 return 0;
240
241 if (!capable(CAP_SYS_ADMIN))
242 return -EACCES;
243
244 return 0;
245}
246
247int drm_setmaster_ioctl(struct drm_device *dev, void *data,
248 struct drm_file *file_priv)
249{
250 int ret;
251
252 mutex_lock(&dev->master_mutex);
253
254 ret = drm_master_check_perm(dev, file_priv);
255 if (ret)
256 goto out_unlock;
257
258 if (drm_is_current_master_locked(file_priv))
259 goto out_unlock;
260
261 if (dev->master) {
262 ret = -EBUSY;
263 goto out_unlock;
264 }
265
266 if (!file_priv->master) {
267 ret = -EINVAL;
268 goto out_unlock;
269 }
270
271 if (!file_priv->is_master) {
272 ret = drm_new_set_master(dev, file_priv);
273 goto out_unlock;
274 }
275
276 if (file_priv->master->lessor != NULL) {
277 drm_dbg_lease(dev,
278 "Attempt to set lessee %d as master\n",
279 file_priv->master->lessee_id);
280 ret = -EINVAL;
281 goto out_unlock;
282 }
283
284 drm_set_master(dev, file_priv, false);
285out_unlock:
286 mutex_unlock(&dev->master_mutex);
287 return ret;
288}
289
290static void drm_drop_master(struct drm_device *dev,
291 struct drm_file *fpriv)
292{
293 if (dev->driver->master_drop)
294 dev->driver->master_drop(dev, fpriv);
295 drm_master_put(&dev->master);
296}
297
298int drm_dropmaster_ioctl(struct drm_device *dev, void *data,
299 struct drm_file *file_priv)
300{
301 int ret;
302
303 mutex_lock(&dev->master_mutex);
304
305 ret = drm_master_check_perm(dev, file_priv);
306 if (ret)
307 goto out_unlock;
308
309 if (!drm_is_current_master_locked(file_priv)) {
310 ret = -EINVAL;
311 goto out_unlock;
312 }
313
314 if (!dev->master) {
315 ret = -EINVAL;
316 goto out_unlock;
317 }
318
319 if (file_priv->master->lessor != NULL) {
320 drm_dbg_lease(dev,
321 "Attempt to drop lessee %d as master\n",
322 file_priv->master->lessee_id);
323 ret = -EINVAL;
324 goto out_unlock;
325 }
326
327 drm_drop_master(dev, file_priv);
328out_unlock:
329 mutex_unlock(&dev->master_mutex);
330 return ret;
331}
332
333int drm_master_open(struct drm_file *file_priv)
334{
335 struct drm_device *dev = file_priv->minor->dev;
336 int ret = 0;
337
338 /* if there is no current master make this fd it, but do not create
339 * any master object for render clients
340 */
341 mutex_lock(&dev->master_mutex);
342 if (!dev->master) {
343 ret = drm_new_set_master(dev, file_priv);
344 } else {
345 spin_lock(&file_priv->master_lookup_lock);
346 file_priv->master = drm_master_get(dev->master);
347 spin_unlock(&file_priv->master_lookup_lock);
348 }
349 mutex_unlock(&dev->master_mutex);
350
351 return ret;
352}
353
354void drm_master_release(struct drm_file *file_priv)
355{
356 struct drm_device *dev = file_priv->minor->dev;
357 struct drm_master *master;
358
359 mutex_lock(&dev->master_mutex);
360 master = file_priv->master;
361 if (file_priv->magic)
362 idr_remove(&file_priv->master->magic_map, file_priv->magic);
363
364 if (!drm_is_current_master_locked(file_priv))
365 goto out;
366
367 drm_legacy_lock_master_cleanup(dev, master);
368
369 if (dev->master == file_priv->master)
370 drm_drop_master(dev, file_priv);
371out:
372 if (drm_core_check_feature(dev, DRIVER_MODESET) && file_priv->is_master) {
373 /* Revoke any leases held by this or lessees, but only if
374 * this is the "real" master
375 */
376 drm_lease_revoke(master);
377 }
378
379 /* drop the master reference held by the file priv */
380 if (file_priv->master)
381 drm_master_put(&file_priv->master);
382 mutex_unlock(&dev->master_mutex);
383}
384
385/**
386 * drm_master_get - reference a master pointer
387 * @master: &struct drm_master
388 *
389 * Increments the reference count of @master and returns a pointer to @master.
390 */
391struct drm_master *drm_master_get(struct drm_master *master)
392{
393 kref_get(&master->refcount);
394 return master;
395}
396EXPORT_SYMBOL(drm_master_get);
397
398/**
399 * drm_file_get_master - reference &drm_file.master of @file_priv
400 * @file_priv: DRM file private
401 *
402 * Increments the reference count of @file_priv's &drm_file.master and returns
403 * the &drm_file.master. If @file_priv has no &drm_file.master, returns NULL.
404 *
405 * Master pointers returned from this function should be unreferenced using
406 * drm_master_put().
407 */
408struct drm_master *drm_file_get_master(struct drm_file *file_priv)
409{
410 struct drm_master *master = NULL;
411
412 spin_lock(&file_priv->master_lookup_lock);
413 if (!file_priv->master)
414 goto unlock;
415 master = drm_master_get(file_priv->master);
416
417unlock:
418 spin_unlock(&file_priv->master_lookup_lock);
419 return master;
420}
421EXPORT_SYMBOL(drm_file_get_master);
422
423static void drm_master_destroy(struct kref *kref)
424{
425 struct drm_master *master = container_of(kref, struct drm_master, refcount);
426 struct drm_device *dev = master->dev;
427
428 if (drm_core_check_feature(dev, DRIVER_MODESET))
429 drm_lease_destroy(master);
430
431 drm_legacy_master_rmmaps(dev, master);
432
433 idr_destroy(&master->magic_map);
434 idr_destroy(&master->leases);
435 idr_destroy(&master->lessee_idr);
436
437 kfree(master->unique);
438 kfree(master);
439}
440
441/**
442 * drm_master_put - unreference and clear a master pointer
443 * @master: pointer to a pointer of &struct drm_master
444 *
445 * This decrements the &drm_master behind @master and sets it to NULL.
446 */
447void drm_master_put(struct drm_master **master)
448{
449 kref_put(&(*master)->refcount, drm_master_destroy);
450 *master = NULL;
451}
452EXPORT_SYMBOL(drm_master_put);
453
454/* Used by drm_client and drm_fb_helper */
455bool drm_master_internal_acquire(struct drm_device *dev)
456{
457 mutex_lock(&dev->master_mutex);
458 if (dev->master) {
459 mutex_unlock(&dev->master_mutex);
460 return false;
461 }
462
463 return true;
464}
465EXPORT_SYMBOL(drm_master_internal_acquire);
466
467/* Used by drm_client and drm_fb_helper */
468void drm_master_internal_release(struct drm_device *dev)
469{
470 mutex_unlock(&dev->master_mutex);
471}
472EXPORT_SYMBOL(drm_master_internal_release);