1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * Copyright © 2017 Keith Packard <keithp@keithp.com>
4 */
5#include <linux/file.h>
6#include <linux/uaccess.h>
7
8#include <drm/drm_auth.h>
9#include <drm/drm_crtc.h>
10#include <drm/drm_drv.h>
11#include <drm/drm_file.h>
12#include <drm/drm_lease.h>
13#include <drm/drm_print.h>
14
15#include "drm_crtc_internal.h"
16#include "drm_internal.h"
17
18/**
19 * DOC: drm leasing
20 *
21 * DRM leases provide information about whether a DRM master may control a DRM
22 * mode setting object. This enables the creation of multiple DRM masters that
23 * manage subsets of display resources.
24 *
25 * The original DRM master of a device 'owns' the available drm resources. It
26 * may create additional DRM masters and 'lease' resources which it controls
27 * to the new DRM master. This gives the new DRM master control over the
28 * leased resources until the owner revokes the lease, or the new DRM master
29 * is closed. Some helpful terminology:
30 *
31 * - An 'owner' is a &struct drm_master that is not leasing objects from
32 * another &struct drm_master, and hence 'owns' the objects. The owner can be
33 * identified as the &struct drm_master for which &drm_master.lessor is NULL.
34 *
35 * - A 'lessor' is a &struct drm_master which is leasing objects to one or more
36 * other &struct drm_master. Currently, lessees are not allowed to
37 * create sub-leases, hence the lessor is the same as the owner.
38 *
39 * - A 'lessee' is a &struct drm_master which is leasing objects from some
40 * other &struct drm_master. Each lessee only leases resources from a single
41 * lessor recorded in &drm_master.lessor, and holds the set of objects that
42 * it is leasing in &drm_master.leases.
43 *
44 * - A 'lease' is a contract between the lessor and lessee that identifies
45 * which resources may be controlled by the lessee. All of the resources
46 * that are leased must be owned by or leased to the lessor, and lessors are
47 * not permitted to lease the same object to multiple lessees.
48 *
49 * The set of objects any &struct drm_master 'controls' is limited to the set
50 * of objects it leases (for lessees) or all objects (for owners).
51 *
52 * Objects not controlled by a &struct drm_master cannot be modified through
53 * the various state manipulating ioctls, and any state reported back to user
54 * space will be edited to make them appear idle and/or unusable. For
55 * instance, connectors always report 'disconnected', while encoders
56 * report no possible crtcs or clones.
57 *
58 * Since each lessee may lease objects from a single lessor, display resource
59 * leases form a tree of &struct drm_master. As lessees are currently not
60 * allowed to create sub-leases, the tree depth is limited to 1. All of
61 * these get activated simultaneously when the top level device owner changes
62 * through the SETMASTER or DROPMASTER IOCTL, so &drm_device.master points to
63 * the owner at the top of the lease tree (i.e. the &struct drm_master for which
64 * &drm_master.lessor is NULL). The full list of lessees that are leasing
65 * objects from the owner can be searched via the owner's
66 * &drm_master.lessee_idr.
67 */
68
69#define drm_for_each_lessee(lessee, lessor) \
70 list_for_each_entry((lessee), &(lessor)->lessees, lessee_list)
71
72static uint64_t drm_lease_idr_object;
73
74struct drm_master *drm_lease_owner(struct drm_master *master)
75{
76 while (master->lessor != NULL)
77 master = master->lessor;
78 return master;
79}
80
81static struct drm_master*
82_drm_find_lessee(struct drm_master *master, int lessee_id)
83{
84 lockdep_assert_held(&master->dev->mode_config.idr_mutex);
85 return idr_find(&drm_lease_owner(master)->lessee_idr, id: lessee_id);
86}
87
88static int _drm_lease_held_master(struct drm_master *master, int id)
89{
90 lockdep_assert_held(&master->dev->mode_config.idr_mutex);
91 if (master->lessor)
92 return idr_find(&master->leases, id) != NULL;
93 return true;
94}
95
96/* Checks if the given object has been leased to some lessee of drm_master */
97static bool _drm_has_leased(struct drm_master *master, int id)
98{
99 struct drm_master *lessee;
100
101 lockdep_assert_held(&master->dev->mode_config.idr_mutex);
102 drm_for_each_lessee(lessee, master)
103 if (_drm_lease_held_master(master: lessee, id))
104 return true;
105 return false;
106}
107
108/* Called with idr_mutex held */
109bool _drm_lease_held(struct drm_file *file_priv, int id)
110{
111 bool ret;
112 struct drm_master *master;
113
114 if (!file_priv)
115 return true;
116
117 master = drm_file_get_master(file_priv);
118 if (!master)
119 return true;
120 ret = _drm_lease_held_master(master, id);
121 drm_master_put(master: &master);
122
123 return ret;
124}
125
126bool drm_lease_held(struct drm_file *file_priv, int id)
127{
128 struct drm_master *master;
129 bool ret;
130
131 if (!file_priv)
132 return true;
133
134 master = drm_file_get_master(file_priv);
135 if (!master)
136 return true;
137 if (!master->lessor) {
138 ret = true;
139 goto out;
140 }
141 mutex_lock(&master->dev->mode_config.idr_mutex);
142 ret = _drm_lease_held_master(master, id);
143 mutex_unlock(lock: &master->dev->mode_config.idr_mutex);
144
145out:
146 drm_master_put(master: &master);
147 return ret;
148}
149
150/*
151 * Given a bitmask of crtcs to check, reconstructs a crtc mask based on the
152 * crtcs which are visible through the specified file.
153 */
154uint32_t drm_lease_filter_crtcs(struct drm_file *file_priv, uint32_t crtcs_in)
155{
156 struct drm_master *master;
157 struct drm_device *dev;
158 struct drm_crtc *crtc;
159 int count_in, count_out;
160 uint32_t crtcs_out = 0;
161
162 if (!file_priv)
163 return crtcs_in;
164
165 master = drm_file_get_master(file_priv);
166 if (!master)
167 return crtcs_in;
168 if (!master->lessor) {
169 crtcs_out = crtcs_in;
170 goto out;
171 }
172 dev = master->dev;
173
174 count_in = count_out = 0;
175 mutex_lock(&master->dev->mode_config.idr_mutex);
176 list_for_each_entry(crtc, &dev->mode_config.crtc_list, head) {
177 if (_drm_lease_held_master(master, id: crtc->base.id)) {
178 uint32_t mask_in = 1ul << count_in;
179
180 if ((crtcs_in & mask_in) != 0) {
181 uint32_t mask_out = 1ul << count_out;
182
183 crtcs_out |= mask_out;
184 }
185 count_out++;
186 }
187 count_in++;
188 }
189 mutex_unlock(lock: &master->dev->mode_config.idr_mutex);
190
191out:
192 drm_master_put(master: &master);
193 return crtcs_out;
194}
195
196/*
197 * Uses drm_master_create to allocate a new drm_master, then checks to
198 * make sure all of the desired objects can be leased, atomically
199 * leasing them to the new drmmaster.
200 *
201 * ERR_PTR(-EACCES) some other master holds the title to any object
202 * ERR_PTR(-ENOENT) some object is not a valid DRM object for this device
203 * ERR_PTR(-EBUSY) some other lessee holds title to this object
204 * ERR_PTR(-EEXIST) same object specified more than once in the provided list
205 * ERR_PTR(-ENOMEM) allocation failed
206 */
207static struct drm_master *drm_lease_create(struct drm_master *lessor, struct idr *leases)
208{
209 struct drm_device *dev = lessor->dev;
210 int error;
211 struct drm_master *lessee;
212 int object;
213 int id;
214 void *entry;
215
216 drm_dbg_lease(dev, "lessor %d\n", lessor->lessee_id);
217
218 lessee = drm_master_create(dev: lessor->dev);
219 if (!lessee) {
220 drm_dbg_lease(dev, "drm_master_create failed\n");
221 return ERR_PTR(error: -ENOMEM);
222 }
223
224 mutex_lock(&dev->mode_config.idr_mutex);
225
226 idr_for_each_entry(leases, entry, object) {
227 error = 0;
228 if (!idr_find(&dev->mode_config.object_idr, id: object))
229 error = -ENOENT;
230 else if (_drm_has_leased(master: lessor, id: object))
231 error = -EBUSY;
232
233 if (error != 0) {
234 drm_dbg_lease(dev, "object %d failed %d\n", object, error);
235 goto out_lessee;
236 }
237 }
238
239 /* Insert the new lessee into the tree */
240 id = idr_alloc(&(drm_lease_owner(master: lessor)->lessee_idr), ptr: lessee, start: 1, end: 0, GFP_KERNEL);
241 if (id < 0) {
242 error = id;
243 goto out_lessee;
244 }
245
246 lessee->lessee_id = id;
247 lessee->lessor = drm_master_get(master: lessor);
248 list_add_tail(new: &lessee->lessee_list, head: &lessor->lessees);
249
250 /* Move the leases over */
251 lessee->leases = *leases;
252 drm_dbg_lease(dev, "new lessee %d %p, lessor %d %p\n",
253 lessee->lessee_id, lessee, lessor->lessee_id, lessor);
254
255 mutex_unlock(lock: &dev->mode_config.idr_mutex);
256 return lessee;
257
258out_lessee:
259 mutex_unlock(lock: &dev->mode_config.idr_mutex);
260
261 drm_master_put(master: &lessee);
262
263 return ERR_PTR(error);
264}
265
266void drm_lease_destroy(struct drm_master *master)
267{
268 struct drm_device *dev = master->dev;
269
270 mutex_lock(&dev->mode_config.idr_mutex);
271
272 drm_dbg_lease(dev, "drm_lease_destroy %d\n", master->lessee_id);
273
274 /* This master is referenced by all lessees, hence it cannot be destroyed
275 * until all of them have been
276 */
277 WARN_ON(!list_empty(&master->lessees));
278
279 /* Remove this master from the lessee idr in the owner */
280 if (master->lessee_id != 0) {
281 drm_dbg_lease(dev, "remove master %d from device list of lessees\n",
282 master->lessee_id);
283 idr_remove(&(drm_lease_owner(master)->lessee_idr), id: master->lessee_id);
284 }
285
286 /* Remove this master from any lessee list it may be on */
287 list_del(entry: &master->lessee_list);
288
289 mutex_unlock(lock: &dev->mode_config.idr_mutex);
290
291 if (master->lessor) {
292 /* Tell the master to check the lessee list */
293 drm_sysfs_lease_event(dev);
294 drm_master_put(master: &master->lessor);
295 }
296
297 drm_dbg_lease(dev, "drm_lease_destroy done %d\n", master->lessee_id);
298}
299
300static void _drm_lease_revoke(struct drm_master *top)
301{
302 int object;
303 void *entry;
304 struct drm_master *master = top;
305
306 lockdep_assert_held(&top->dev->mode_config.idr_mutex);
307
308 /*
309 * Walk the tree starting at 'top' emptying all leases. Because
310 * the tree is fully connected, we can do this without recursing
311 */
312 for (;;) {
313 drm_dbg_lease(master->dev, "revoke leases for %p %d\n",
314 master, master->lessee_id);
315
316 /* Evacuate the lease */
317 idr_for_each_entry(&master->leases, entry, object)
318 idr_remove(&master->leases, id: object);
319
320 /* Depth-first list walk */
321
322 /* Down */
323 if (!list_empty(head: &master->lessees)) {
324 master = list_first_entry(&master->lessees, struct drm_master, lessee_list);
325 } else {
326 /* Up */
327 while (master != top && master == list_last_entry(&master->lessor->lessees, struct drm_master, lessee_list))
328 master = master->lessor;
329
330 if (master == top)
331 break;
332
333 /* Over */
334 master = list_next_entry(master, lessee_list);
335 }
336 }
337}
338
339void drm_lease_revoke(struct drm_master *top)
340{
341 mutex_lock(&top->dev->mode_config.idr_mutex);
342 _drm_lease_revoke(top);
343 mutex_unlock(lock: &top->dev->mode_config.idr_mutex);
344}
345
346static int validate_lease(struct drm_device *dev,
347 int object_count,
348 struct drm_mode_object **objects,
349 bool universal_planes)
350{
351 int o;
352 int has_crtc = -1;
353 int has_connector = -1;
354 int has_plane = -1;
355
356 /* we want to confirm that there is at least one crtc, plane
357 connector object. */
358
359 for (o = 0; o < object_count; o++) {
360 if (objects[o]->type == DRM_MODE_OBJECT_CRTC && has_crtc == -1) {
361 has_crtc = o;
362 }
363 if (objects[o]->type == DRM_MODE_OBJECT_CONNECTOR && has_connector == -1)
364 has_connector = o;
365
366 if (universal_planes) {
367 if (objects[o]->type == DRM_MODE_OBJECT_PLANE && has_plane == -1)
368 has_plane = o;
369 }
370 }
371 if (has_crtc == -1 || has_connector == -1)
372 return -EINVAL;
373 if (universal_planes && has_plane == -1)
374 return -EINVAL;
375 return 0;
376}
377
378static int fill_object_idr(struct drm_device *dev,
379 struct drm_file *lessor_priv,
380 struct idr *leases,
381 int object_count,
382 u32 *object_ids)
383{
384 struct drm_mode_object **objects;
385 u32 o;
386 int ret;
387 bool universal_planes = READ_ONCE(lessor_priv->universal_planes);
388
389 objects = kcalloc(object_count, sizeof(struct drm_mode_object *),
390 GFP_KERNEL);
391 if (!objects)
392 return -ENOMEM;
393
394 /* step one - get references to all the mode objects
395 and check for validity. */
396 for (o = 0; o < object_count; o++) {
397 objects[o] = drm_mode_object_find(dev, file_priv: lessor_priv,
398 id: object_ids[o],
399 DRM_MODE_OBJECT_ANY);
400 if (!objects[o]) {
401 ret = -ENOENT;
402 goto out_free_objects;
403 }
404
405 if (!drm_mode_object_lease_required(type: objects[o]->type)) {
406 DRM_DEBUG_KMS("invalid object for lease\n");
407 ret = -EINVAL;
408 goto out_free_objects;
409 }
410 }
411
412 ret = validate_lease(dev, object_count, objects, universal_planes);
413 if (ret) {
414 drm_dbg_lease(dev, "lease validation failed\n");
415 goto out_free_objects;
416 }
417
418 /* add their IDs to the lease request - taking into account
419 universal planes */
420 for (o = 0; o < object_count; o++) {
421 struct drm_mode_object *obj = objects[o];
422 u32 object_id = objects[o]->id;
423
424 drm_dbg_lease(dev, "Adding object %d to lease\n", object_id);
425
426 /*
427 * We're using an IDR to hold the set of leased
428 * objects, but we don't need to point at the object's
429 * data structure from the lease as the main object_idr
430 * will be used to actually find that. Instead, all we
431 * really want is a 'leased/not-leased' result, for
432 * which any non-NULL pointer will work fine.
433 */
434 ret = idr_alloc(leases, ptr: &drm_lease_idr_object , start: object_id, end: object_id + 1, GFP_KERNEL);
435 if (ret < 0) {
436 drm_dbg_lease(dev, "Object %d cannot be inserted into leases (%d)\n",
437 object_id, ret);
438 goto out_free_objects;
439 }
440 if (obj->type == DRM_MODE_OBJECT_CRTC && !universal_planes) {
441 struct drm_crtc *crtc = obj_to_crtc(obj);
442
443 ret = idr_alloc(leases, ptr: &drm_lease_idr_object, start: crtc->primary->base.id, end: crtc->primary->base.id + 1, GFP_KERNEL);
444 if (ret < 0) {
445 drm_dbg_lease(dev, "Object primary plane %d cannot be inserted into leases (%d)\n",
446 object_id, ret);
447 goto out_free_objects;
448 }
449 if (crtc->cursor) {
450 ret = idr_alloc(leases, ptr: &drm_lease_idr_object, start: crtc->cursor->base.id, end: crtc->cursor->base.id + 1, GFP_KERNEL);
451 if (ret < 0) {
452 drm_dbg_lease(dev, "Object cursor plane %d cannot be inserted into leases (%d)\n",
453 object_id, ret);
454 goto out_free_objects;
455 }
456 }
457 }
458 }
459
460 ret = 0;
461out_free_objects:
462 for (o = 0; o < object_count; o++) {
463 if (objects[o])
464 drm_mode_object_put(obj: objects[o]);
465 }
466 kfree(objp: objects);
467 return ret;
468}
469
470/*
471 * The master associated with the specified file will have a lease
472 * created containing the objects specified in the ioctl structure.
473 * A file descriptor will be allocated for that and returned to the
474 * application.
475 */
476int drm_mode_create_lease_ioctl(struct drm_device *dev,
477 void *data, struct drm_file *lessor_priv)
478{
479 struct drm_mode_create_lease *cl = data;
480 size_t object_count;
481 int ret = 0;
482 struct idr leases;
483 struct drm_master *lessor;
484 struct drm_master *lessee = NULL;
485 struct file *lessee_file = NULL;
486 struct file *lessor_file = lessor_priv->filp;
487 struct drm_file *lessee_priv;
488 int fd = -1;
489 uint32_t *object_ids;
490
491 /* Can't lease without MODESET */
492 if (!drm_core_check_feature(dev, feature: DRIVER_MODESET))
493 return -EOPNOTSUPP;
494
495 if (cl->flags && (cl->flags & ~(O_CLOEXEC | O_NONBLOCK))) {
496 drm_dbg_lease(dev, "invalid flags\n");
497 return -EINVAL;
498 }
499
500 lessor = drm_file_get_master(file_priv: lessor_priv);
501 /* Do not allow sub-leases */
502 if (lessor->lessor) {
503 drm_dbg_lease(dev, "recursive leasing not allowed\n");
504 ret = -EINVAL;
505 goto out_lessor;
506 }
507
508 object_count = cl->object_count;
509
510 /* Handle leased objects, if any */
511 idr_init(idr: &leases);
512 if (object_count != 0) {
513 object_ids = memdup_array_user(u64_to_user_ptr(cl->object_ids),
514 n: object_count, size: sizeof(__u32));
515 if (IS_ERR(ptr: object_ids)) {
516 ret = PTR_ERR(ptr: object_ids);
517 idr_destroy(&leases);
518 goto out_lessor;
519 }
520
521 /* fill and validate the object idr */
522 ret = fill_object_idr(dev, lessor_priv, leases: &leases,
523 object_count, object_ids);
524 kfree(objp: object_ids);
525 if (ret) {
526 drm_dbg_lease(dev, "lease object lookup failed: %i\n", ret);
527 idr_destroy(&leases);
528 goto out_lessor;
529 }
530 }
531
532 /* Allocate a file descriptor for the lease */
533 fd = get_unused_fd_flags(flags: cl->flags & (O_CLOEXEC | O_NONBLOCK));
534 if (fd < 0) {
535 idr_destroy(&leases);
536 ret = fd;
537 goto out_lessor;
538 }
539
540 drm_dbg_lease(dev, "Creating lease\n");
541 /* lessee will take the ownership of leases */
542 lessee = drm_lease_create(lessor, leases: &leases);
543
544 if (IS_ERR(ptr: lessee)) {
545 ret = PTR_ERR(ptr: lessee);
546 idr_destroy(&leases);
547 goto out_leases;
548 }
549
550 /* Clone the lessor file to create a new file for us */
551 drm_dbg_lease(dev, "Allocating lease file\n");
552 lessee_file = file_clone_open(file: lessor_file);
553 if (IS_ERR(ptr: lessee_file)) {
554 ret = PTR_ERR(ptr: lessee_file);
555 goto out_lessee;
556 }
557
558 lessee_priv = lessee_file->private_data;
559 /* Change the file to a master one */
560 drm_master_put(master: &lessee_priv->master);
561 lessee_priv->master = lessee;
562 lessee_priv->is_master = 1;
563 lessee_priv->authenticated = 1;
564
565 /* Pass fd back to userspace */
566 drm_dbg_lease(dev, "Returning fd %d id %d\n", fd, lessee->lessee_id);
567 cl->fd = fd;
568 cl->lessee_id = lessee->lessee_id;
569
570 /* Hook up the fd */
571 fd_install(fd, file: lessee_file);
572
573 drm_master_put(master: &lessor);
574 drm_dbg_lease(dev, "drm_mode_create_lease_ioctl succeeded\n");
575 return 0;
576
577out_lessee:
578 drm_master_put(master: &lessee);
579
580out_leases:
581 put_unused_fd(fd);
582
583out_lessor:
584 drm_master_put(master: &lessor);
585 drm_dbg_lease(dev, "drm_mode_create_lease_ioctl failed: %d\n", ret);
586 return ret;
587}
588
589int drm_mode_list_lessees_ioctl(struct drm_device *dev,
590 void *data, struct drm_file *lessor_priv)
591{
592 struct drm_mode_list_lessees *arg = data;
593 __u32 __user *lessee_ids = (__u32 __user *) (uintptr_t) (arg->lessees_ptr);
594 __u32 count_lessees = arg->count_lessees;
595 struct drm_master *lessor, *lessee;
596 int count;
597 int ret = 0;
598
599 if (arg->pad)
600 return -EINVAL;
601
602 /* Can't lease without MODESET */
603 if (!drm_core_check_feature(dev, feature: DRIVER_MODESET))
604 return -EOPNOTSUPP;
605
606 lessor = drm_file_get_master(file_priv: lessor_priv);
607 drm_dbg_lease(dev, "List lessees for %d\n", lessor->lessee_id);
608
609 mutex_lock(&dev->mode_config.idr_mutex);
610
611 count = 0;
612 drm_for_each_lessee(lessee, lessor) {
613 /* Only list un-revoked leases */
614 if (!idr_is_empty(idr: &lessee->leases)) {
615 if (count_lessees > count) {
616 drm_dbg_lease(dev, "Add lessee %d\n",
617 lessee->lessee_id);
618 ret = put_user(lessee->lessee_id, lessee_ids + count);
619 if (ret)
620 break;
621 }
622 count++;
623 }
624 }
625
626 drm_dbg_lease(dev, "Lessor leases to %d\n", count);
627 if (ret == 0)
628 arg->count_lessees = count;
629
630 mutex_unlock(lock: &dev->mode_config.idr_mutex);
631 drm_master_put(master: &lessor);
632
633 return ret;
634}
635
636/* Return the list of leased objects for the specified lessee */
637int drm_mode_get_lease_ioctl(struct drm_device *dev,
638 void *data, struct drm_file *lessee_priv)
639{
640 struct drm_mode_get_lease *arg = data;
641 __u32 __user *object_ids = (__u32 __user *) (uintptr_t) (arg->objects_ptr);
642 __u32 count_objects = arg->count_objects;
643 struct drm_master *lessee;
644 struct idr *object_idr;
645 int count;
646 void *entry;
647 int object;
648 int ret = 0;
649
650 if (arg->pad)
651 return -EINVAL;
652
653 /* Can't lease without MODESET */
654 if (!drm_core_check_feature(dev, feature: DRIVER_MODESET))
655 return -EOPNOTSUPP;
656
657 lessee = drm_file_get_master(file_priv: lessee_priv);
658 drm_dbg_lease(dev, "get lease for %d\n", lessee->lessee_id);
659
660 mutex_lock(&dev->mode_config.idr_mutex);
661
662 if (lessee->lessor == NULL)
663 /* owner can use all objects */
664 object_idr = &lessee->dev->mode_config.object_idr;
665 else
666 /* lessee can only use allowed object */
667 object_idr = &lessee->leases;
668
669 count = 0;
670 idr_for_each_entry(object_idr, entry, object) {
671 if (count_objects > count) {
672 drm_dbg_lease(dev, "adding object %d\n", object);
673 ret = put_user(object, object_ids + count);
674 if (ret)
675 break;
676 }
677 count++;
678 }
679
680 DRM_DEBUG("lease holds %d objects\n", count);
681 if (ret == 0)
682 arg->count_objects = count;
683
684 mutex_unlock(lock: &dev->mode_config.idr_mutex);
685 drm_master_put(master: &lessee);
686
687 return ret;
688}
689
690/*
691 * This removes all of the objects from the lease without
692 * actually getting rid of the lease itself; that way all
693 * references to it still work correctly
694 */
695int drm_mode_revoke_lease_ioctl(struct drm_device *dev,
696 void *data, struct drm_file *lessor_priv)
697{
698 struct drm_mode_revoke_lease *arg = data;
699 struct drm_master *lessor;
700 struct drm_master *lessee;
701 int ret = 0;
702
703 drm_dbg_lease(dev, "revoke lease for %d\n", arg->lessee_id);
704
705 /* Can't lease without MODESET */
706 if (!drm_core_check_feature(dev, feature: DRIVER_MODESET))
707 return -EOPNOTSUPP;
708
709 lessor = drm_file_get_master(file_priv: lessor_priv);
710 mutex_lock(&dev->mode_config.idr_mutex);
711
712 lessee = _drm_find_lessee(master: lessor, lessee_id: arg->lessee_id);
713
714 /* No such lessee */
715 if (!lessee) {
716 ret = -ENOENT;
717 goto fail;
718 }
719
720 /* Lease is not held by lessor */
721 if (lessee->lessor != lessor) {
722 ret = -EACCES;
723 goto fail;
724 }
725
726 _drm_lease_revoke(top: lessee);
727
728fail:
729 mutex_unlock(lock: &dev->mode_config.idr_mutex);
730 drm_master_put(master: &lessor);
731
732 return ret;
733}
734

source code of linux/drivers/gpu/drm/drm_lease.c