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