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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
139 lockdep_assert_held_once(&dev->master_mutex);
140
141 WARN_ON(fpriv->is_master);
142 old_master = fpriv->master;
143 fpriv->master = drm_master_create(dev);
144 if (!fpriv->master) {
145 fpriv->master = old_master;
146 return -ENOMEM;
147 }
148
149 fpriv->is_master = 1;
150 fpriv->authenticated = 1;
151
152 drm_set_master(dev, fpriv, true);
153
154 if (old_master)
155 drm_master_put(&old_master);
156
157 return 0;
158}
159
160/*
161 * In the olden days the SET/DROP_MASTER ioctls used to return EACCES when
162 * CAP_SYS_ADMIN was not set. This was used to prevent rogue applications
163 * from becoming master and/or failing to release it.
164 *
165 * At the same time, the first client (for a given VT) is _always_ master.
166 * Thus in order for the ioctls to succeed, one had to _explicitly_ run the
167 * application as root or flip the setuid bit.
168 *
169 * If the CAP_SYS_ADMIN was missing, no other client could become master...
170 * EVER :-( Leading to a) the graphics session dying badly or b) a completely
171 * locked session.
172 *
173 *
174 * As some point systemd-logind was introduced to orchestrate and delegate
175 * master as applicable. It does so by opening the fd and passing it to users
176 * while in itself logind a) does the set/drop master per users' request and
177 * b) * implicitly drops master on VT switch.
178 *
179 * Even though logind looks like the future, there are a few issues:
180 * - some platforms don't have equivalent (Android, CrOS, some BSDs) so
181 * root is required _solely_ for SET/DROP MASTER.
182 * - applications may not be updated to use it,
183 * - any client which fails to drop master* can DoS the application using
184 * logind, to a varying degree.
185 *
186 * * Either due missing CAP_SYS_ADMIN or simply not calling DROP_MASTER.
187 *
188 *
189 * Here we implement the next best thing:
190 * - ensure the logind style of fd passing works unchanged, and
191 * - allow a client to drop/set master, iff it is/was master at a given point
192 * in time.
193 *
194 * Note: DROP_MASTER cannot be free for all, as an arbitrator user could:
195 * - DoS/crash the arbitrator - details would be implementation specific
196 * - open the node, become master implicitly and cause issues
197 *
198 * As a result this fixes the following when using root-less build w/o logind
199 * - startx
200 * - weston
201 * - various compositors based on wlroots
202 */
203static int
204drm_master_check_perm(struct drm_device *dev, struct drm_file *file_priv)
205{
206 if (file_priv->pid == task_pid(current) && file_priv->was_master)
207 return 0;
208
209 if (!capable(CAP_SYS_ADMIN))
210 return -EACCES;
211
212 return 0;
213}
214
215int drm_setmaster_ioctl(struct drm_device *dev, void *data,
216 struct drm_file *file_priv)
217{
218 int ret;
219
220 mutex_lock(&dev->master_mutex);
221
222 ret = drm_master_check_perm(dev, file_priv);
223 if (ret)
224 goto out_unlock;
225
226 if (drm_is_current_master(file_priv))
227 goto out_unlock;
228
229 if (dev->master) {
230 ret = -EBUSY;
231 goto out_unlock;
232 }
233
234 if (!file_priv->master) {
235 ret = -EINVAL;
236 goto out_unlock;
237 }
238
239 if (!file_priv->is_master) {
240 ret = drm_new_set_master(dev, file_priv);
241 goto out_unlock;
242 }
243
244 if (file_priv->master->lessor != NULL) {
245 DRM_DEBUG_LEASE("Attempt to set lessee %d as master\n", file_priv->master->lessee_id);
246 ret = -EINVAL;
247 goto out_unlock;
248 }
249
250 drm_set_master(dev, file_priv, false);
251out_unlock:
252 mutex_unlock(&dev->master_mutex);
253 return ret;
254}
255
256static void drm_drop_master(struct drm_device *dev,
257 struct drm_file *fpriv)
258{
259 if (dev->driver->master_drop)
260 dev->driver->master_drop(dev, fpriv);
261 drm_master_put(&dev->master);
262}
263
264int drm_dropmaster_ioctl(struct drm_device *dev, void *data,
265 struct drm_file *file_priv)
266{
267 int ret;
268
269 mutex_lock(&dev->master_mutex);
270
271 ret = drm_master_check_perm(dev, file_priv);
272 if (ret)
273 goto out_unlock;
274
275 if (!drm_is_current_master(file_priv)) {
276 ret = -EINVAL;
277 goto out_unlock;
278 }
279
280 if (!dev->master) {
281 ret = -EINVAL;
282 goto out_unlock;
283 }
284
285 if (file_priv->master->lessor != NULL) {
286 DRM_DEBUG_LEASE("Attempt to drop lessee %d as master\n", file_priv->master->lessee_id);
287 ret = -EINVAL;
288 goto out_unlock;
289 }
290
291 drm_drop_master(dev, file_priv);
292out_unlock:
293 mutex_unlock(&dev->master_mutex);
294 return ret;
295}
296
297int drm_master_open(struct drm_file *file_priv)
298{
299 struct drm_device *dev = file_priv->minor->dev;
300 int ret = 0;
301
302 /* if there is no current master make this fd it, but do not create
303 * any master object for render clients */
304 mutex_lock(&dev->master_mutex);
305 if (!dev->master)
306 ret = drm_new_set_master(dev, file_priv);
307 else
308 file_priv->master = drm_master_get(dev->master);
309 mutex_unlock(&dev->master_mutex);
310
311 return ret;
312}
313
314void drm_master_release(struct drm_file *file_priv)
315{
316 struct drm_device *dev = file_priv->minor->dev;
317 struct drm_master *master = file_priv->master;
318
319 mutex_lock(&dev->master_mutex);
320 if (file_priv->magic)
321 idr_remove(&file_priv->master->magic_map, file_priv->magic);
322
323 if (!drm_is_current_master(file_priv))
324 goto out;
325
326 drm_legacy_lock_master_cleanup(dev, master);
327
328 if (dev->master == file_priv->master)
329 drm_drop_master(dev, file_priv);
330out:
331 if (drm_core_check_feature(dev, DRIVER_MODESET) && file_priv->is_master) {
332 /* Revoke any leases held by this or lessees, but only if
333 * this is the "real" master
334 */
335 drm_lease_revoke(master);
336 }
337
338 /* drop the master reference held by the file priv */
339 if (file_priv->master)
340 drm_master_put(&file_priv->master);
341 mutex_unlock(&dev->master_mutex);
342}
343
344/**
345 * drm_is_current_master - checks whether @priv is the current master
346 * @fpriv: DRM file private
347 *
348 * Checks whether @fpriv is current master on its device. This decides whether a
349 * client is allowed to run DRM_MASTER IOCTLs.
350 *
351 * Most of the modern IOCTL which require DRM_MASTER are for kernel modesetting
352 * - the current master is assumed to own the non-shareable display hardware.
353 */
354bool drm_is_current_master(struct drm_file *fpriv)
355{
356 return fpriv->is_master && drm_lease_owner(fpriv->master) == fpriv->minor->dev->master;
357}
358EXPORT_SYMBOL(drm_is_current_master);
359
360/**
361 * drm_master_get - reference a master pointer
362 * @master: &struct drm_master
363 *
364 * Increments the reference count of @master and returns a pointer to @master.
365 */
366struct drm_master *drm_master_get(struct drm_master *master)
367{
368 kref_get(&master->refcount);
369 return master;
370}
371EXPORT_SYMBOL(drm_master_get);
372
373static void drm_master_destroy(struct kref *kref)
374{
375 struct drm_master *master = container_of(kref, struct drm_master, refcount);
376 struct drm_device *dev = master->dev;
377
378 if (drm_core_check_feature(dev, DRIVER_MODESET))
379 drm_lease_destroy(master);
380
381 drm_legacy_master_rmmaps(dev, master);
382
383 idr_destroy(&master->magic_map);
384 idr_destroy(&master->leases);
385 idr_destroy(&master->lessee_idr);
386
387 kfree(master->unique);
388 kfree(master);
389}
390
391/**
392 * drm_master_put - unreference and clear a master pointer
393 * @master: pointer to a pointer of &struct drm_master
394 *
395 * This decrements the &drm_master behind @master and sets it to NULL.
396 */
397void drm_master_put(struct drm_master **master)
398{
399 kref_put(&(*master)->refcount, drm_master_destroy);
400 *master = NULL;
401}
402EXPORT_SYMBOL(drm_master_put);
403
404/* Used by drm_client and drm_fb_helper */
405bool drm_master_internal_acquire(struct drm_device *dev)
406{
407 mutex_lock(&dev->master_mutex);
408 if (dev->master) {
409 mutex_unlock(&dev->master_mutex);
410 return false;
411 }
412
413 return true;
414}
415EXPORT_SYMBOL(drm_master_internal_acquire);
416
417/* Used by drm_client and drm_fb_helper */
418void drm_master_internal_release(struct drm_device *dev)
419{
420 mutex_unlock(&dev->master_mutex);
421}
422EXPORT_SYMBOL(drm_master_internal_release);
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 <drm/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 */
104int 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 * This ioctl needs protection by the drm_global_mutex, which protects
140 * struct drm_file::magic and struct drm_magic_entry::priv.
141 */
142int drm_getmagic(struct drm_device *dev, void *data, struct drm_file *file_priv)
143{
144 static drm_magic_t sequence = 0;
145 static DEFINE_SPINLOCK(lock);
146 struct drm_auth *auth = data;
147
148 /* Find unique magic */
149 if (file_priv->magic) {
150 auth->magic = file_priv->magic;
151 } else {
152 do {
153 spin_lock(&lock);
154 if (!sequence)
155 ++sequence; /* reserve 0 */
156 auth->magic = sequence++;
157 spin_unlock(&lock);
158 } while (drm_find_file(file_priv->master, auth->magic));
159 file_priv->magic = auth->magic;
160 drm_add_magic(file_priv->master, file_priv, auth->magic);
161 }
162
163 DRM_DEBUG("%u\n", auth->magic);
164
165 return 0;
166}
167
168/**
169 * Authenticate with a magic.
170 *
171 * \param inode device inode.
172 * \param file_priv DRM file private.
173 * \param cmd command.
174 * \param arg pointer to a drm_auth structure.
175 * \return zero if authentication successed, or a negative number otherwise.
176 *
177 * Checks if \p file_priv is associated with the magic number passed in \arg.
178 * This ioctl needs protection by the drm_global_mutex, which protects
179 * struct drm_file::magic and struct drm_magic_entry::priv.
180 */
181int drm_authmagic(struct drm_device *dev, void *data,
182 struct drm_file *file_priv)
183{
184 struct drm_auth *auth = data;
185 struct drm_file *file;
186
187 DRM_DEBUG("%u\n", auth->magic);
188 if ((file = drm_find_file(file_priv->master, auth->magic))) {
189 file->authenticated = 1;
190 drm_remove_magic(file_priv->master, auth->magic);
191 return 0;
192 }
193 return -EINVAL;
194}