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 mutex_lock(&dev->master_mutex); 307 if (!dev->master) { 308 ret = drm_new_set_master(dev, file_priv); 309 } else { 310 spin_lock(&file_priv->master_lookup_lock); 311 file_priv->master = drm_master_get(dev->master); 312 spin_unlock(&file_priv->master_lookup_lock); 313 } 314 mutex_unlock(&dev->master_mutex); 315 316 return ret; 317} 318 319void drm_master_release(struct drm_file *file_priv) 320{ 321 struct drm_device *dev = file_priv->minor->dev; 322 struct drm_master *master; 323 324 mutex_lock(&dev->master_mutex); 325 master = file_priv->master; 326 if (file_priv->magic) 327 idr_remove(&file_priv->master->magic_map, file_priv->magic); 328 329 if (!drm_is_current_master(file_priv)) 330 goto out; 331 332 drm_legacy_lock_master_cleanup(dev, master); 333 334 if (dev->master == file_priv->master) 335 drm_drop_master(dev, file_priv); 336out: 337 if (drm_core_check_feature(dev, DRIVER_MODESET) && file_priv->is_master) { 338 /* Revoke any leases held by this or lessees, but only if 339 * this is the "real" master 340 */ 341 drm_lease_revoke(master); 342 } 343 344 /* drop the master reference held by the file priv */ 345 if (file_priv->master) 346 drm_master_put(&file_priv->master); 347 mutex_unlock(&dev->master_mutex); 348} 349 350/** 351 * drm_is_current_master - checks whether @priv is the current master 352 * @fpriv: DRM file private 353 * 354 * Checks whether @fpriv is current master on its device. This decides whether a 355 * client is allowed to run DRM_MASTER IOCTLs. 356 * 357 * Most of the modern IOCTL which require DRM_MASTER are for kernel modesetting 358 * - the current master is assumed to own the non-shareable display hardware. 359 */ 360bool drm_is_current_master(struct drm_file *fpriv) 361{ 362 return fpriv->is_master && drm_lease_owner(fpriv->master) == fpriv->minor->dev->master; 363} 364EXPORT_SYMBOL(drm_is_current_master); 365 366/** 367 * drm_master_get - reference a master pointer 368 * @master: &struct drm_master 369 * 370 * Increments the reference count of @master and returns a pointer to @master. 371 */ 372struct drm_master *drm_master_get(struct drm_master *master) 373{ 374 kref_get(&master->refcount); 375 return master; 376} 377EXPORT_SYMBOL(drm_master_get); 378 379/** 380 * drm_file_get_master - reference &drm_file.master of @file_priv 381 * @file_priv: DRM file private 382 * 383 * Increments the reference count of @file_priv's &drm_file.master and returns 384 * the &drm_file.master. If @file_priv has no &drm_file.master, returns NULL. 385 * 386 * Master pointers returned from this function should be unreferenced using 387 * drm_master_put(). 388 */ 389struct drm_master *drm_file_get_master(struct drm_file *file_priv) 390{ 391 struct drm_master *master = NULL; 392 393 spin_lock(&file_priv->master_lookup_lock); 394 if (!file_priv->master) 395 goto unlock; 396 master = drm_master_get(file_priv->master); 397 398unlock: 399 spin_unlock(&file_priv->master_lookup_lock); 400 return master; 401} 402EXPORT_SYMBOL(drm_file_get_master); 403 404static void drm_master_destroy(struct kref *kref) 405{ 406 struct drm_master *master = container_of(kref, struct drm_master, refcount); 407 struct drm_device *dev = master->dev; 408 409 if (drm_core_check_feature(dev, DRIVER_MODESET)) 410 drm_lease_destroy(master); 411 412 drm_legacy_master_rmmaps(dev, master); 413 414 idr_destroy(&master->magic_map); 415 idr_destroy(&master->leases); 416 idr_destroy(&master->lessee_idr); 417 418 kfree(master->unique); 419 kfree(master); 420} 421 422/** 423 * drm_master_put - unreference and clear a master pointer 424 * @master: pointer to a pointer of &struct drm_master 425 * 426 * This decrements the &drm_master behind @master and sets it to NULL. 427 */ 428void drm_master_put(struct drm_master **master) 429{ 430 kref_put(&(*master)->refcount, drm_master_destroy); 431 *master = NULL; 432} 433EXPORT_SYMBOL(drm_master_put); 434 435/* Used by drm_client and drm_fb_helper */ 436bool drm_master_internal_acquire(struct drm_device *dev) 437{ 438 mutex_lock(&dev->master_mutex); 439 if (dev->master) { 440 mutex_unlock(&dev->master_mutex); 441 return false; 442 } 443 444 return true; 445} 446EXPORT_SYMBOL(drm_master_internal_acquire); 447 448/* Used by drm_client and drm_fb_helper */ 449void drm_master_internal_release(struct drm_device *dev) 450{ 451 mutex_unlock(&dev->master_mutex); 452} 453EXPORT_SYMBOL(drm_master_internal_release); 454