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1/*2 * Created: Tue Feb 2 08:37:54 1999 by faith@valinux.com3 *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 a12 * copy of this software and associated documentation files (the "Software"),13 * to deal in the Software without restriction, including without limitation14 * the rights to use, copy, modify, merge, publish, distribute, sublicense,15 * and/or sell copies of the Software, and to permit persons to whom the16 * Software is furnished to do so, subject to the following conditions:17 *18 * The above copyright notice and this permission notice (including the next19 * paragraph) shall be included in all copies or substantial portions of the20 * Software.21 *22 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR23 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,24 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL25 * VA LINUX SYSTEMS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM, DAMAGES OR26 * 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 OR28 * 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 authentication43 *44 * &struct drm_master is used to track groups of clients with open45 * primary device nodes. For every &struct drm_file which has had at46 * least once successfully became the device master (either through the47 * SET_MASTER IOCTL, or implicitly through opening the primary device node when48 * 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 pointer50 * 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, or54 * implicitly through closing/opening the primary device node. See also55 * 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 mutually60 * 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 master73 * @fpriv: DRM file private74 *75 * Checks whether @fpriv is current master on its device. This decides whether a76 * client is allowed to run DRM_MASTER IOCTLs.77 *78 * Most of the modern IOCTL which require DRM_MASTER are for kernel modesetting79 * - 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 when192 * CAP_SYS_ADMIN was not set. This was used to prevent rogue applications193 * 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 the197 * 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 completely201 * locked session.202 *203 *204 * As some point systemd-logind was introduced to orchestrate and delegate205 * master as applicable. It does so by opening the fd and passing it to users206 * while in itself logind a) does the set/drop master per users' request and207 * 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) so211 * 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 using214 * 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, and221 * - allow a client to drop/set master, iff it is/was master at a given point222 * 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 specific226 * - open the node, become master implicitly and cause issues227 *228 * As a result this fixes the following when using root-less build w/o logind229 * - startx230 * - weston231 * - various compositors based on wlroots232 */233static int234drm_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 create338 * any master object for render clients339 */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 if371 * this is the "real" master372 */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 pointer384 * @master: &struct drm_master385 *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_priv397 * @file_priv: DRM file private398 *399 * Increments the reference count of @file_priv's &drm_file.master and returns400 * 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 using403 * 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 pointer438 * @master: pointer to a pointer of &struct drm_master439 *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);468