/* * Created: Tue Feb 2 08:37:54 1999 by [email protected] * * Copyright 1999 Precision Insight, Inc., Cedar Park, Texas. * Copyright 2000 VA Linux Systems, Inc., Sunnyvale, California. * All Rights Reserved. * * Author Rickard E. (Rik) Faith <[email protected]> * Author Gareth Hughes <[email protected]> * * Permission is hereby granted, free of charge, to any person obtaining a * copy of this software and associated documentation files (the "Software"), * to deal in the Software without restriction, including without limitation * the rights to use, copy, modify, merge, publish, distribute, sublicense, * and/or sell copies of the Software, and to permit persons to whom the * Software is furnished to do so, subject to the following conditions: * * The above copyright notice and this permission notice (including the next * paragraph) shall be included in all copies or substantial portions of the * Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL * VA LINUX SYSTEMS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM, DAMAGES OR * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR * OTHER DEALINGS IN THE SOFTWARE. */ #include <linux/slab.h> #include <drm/drm_auth.h> #include <drm/drm_drv.h> #include <drm/drm_file.h> #include <drm/drm_lease.h> #include <drm/drm_print.h> #include "drm_internal.h" /** * DOC: master and authentication * * &struct drm_master is used to track groups of clients with open * primary device nodes. For every &struct drm_file which has had at * least once successfully became the device master (either through the * SET_MASTER IOCTL, or implicitly through opening the primary device node when * no one else is the current master that time) there exists one &drm_master. * This is noted in &drm_file.is_master. All other clients have just a pointer * to the &drm_master they are associated with. * * In addition only one &drm_master can be the current master for a &drm_device. * It can be switched through the DROP_MASTER and SET_MASTER IOCTL, or * implicitly through closing/opening the primary device node. See also * drm_is_current_master(). * * Clients can authenticate against the current master (if it matches their own) * using the GETMAGIC and AUTHMAGIC IOCTLs. Together with exchanging masters, * this allows controlled access to the device for an entire group of mutually * trusted clients. */ static bool drm_is_current_master_locked(struct drm_file *fpriv) { … } /** * drm_is_current_master - checks whether @priv is the current master * @fpriv: DRM file private * * Checks whether @fpriv is current master on its device. This decides whether a * client is allowed to run DRM_MASTER IOCTLs. * * Most of the modern IOCTL which require DRM_MASTER are for kernel modesetting * - the current master is assumed to own the non-shareable display hardware. */ bool drm_is_current_master(struct drm_file *fpriv) { … } EXPORT_SYMBOL(…); int drm_getmagic(struct drm_device *dev, void *data, struct drm_file *file_priv) { … } int drm_authmagic(struct drm_device *dev, void *data, struct drm_file *file_priv) { … } struct drm_master *drm_master_create(struct drm_device *dev) { … } static void drm_set_master(struct drm_device *dev, struct drm_file *fpriv, bool new_master) { … } static int drm_new_set_master(struct drm_device *dev, struct drm_file *fpriv) { … } /* * In the olden days the SET/DROP_MASTER ioctls used to return EACCES when * CAP_SYS_ADMIN was not set. This was used to prevent rogue applications * from becoming master and/or failing to release it. * * At the same time, the first client (for a given VT) is _always_ master. * Thus in order for the ioctls to succeed, one had to _explicitly_ run the * application as root or flip the setuid bit. * * If the CAP_SYS_ADMIN was missing, no other client could become master... * EVER :-( Leading to a) the graphics session dying badly or b) a completely * locked session. * * * As some point systemd-logind was introduced to orchestrate and delegate * master as applicable. It does so by opening the fd and passing it to users * while in itself logind a) does the set/drop master per users' request and * b) * implicitly drops master on VT switch. * * Even though logind looks like the future, there are a few issues: * - some platforms don't have equivalent (Android, CrOS, some BSDs) so * root is required _solely_ for SET/DROP MASTER. * - applications may not be updated to use it, * - any client which fails to drop master* can DoS the application using * logind, to a varying degree. * * * Either due missing CAP_SYS_ADMIN or simply not calling DROP_MASTER. * * * Here we implement the next best thing: * - ensure the logind style of fd passing works unchanged, and * - allow a client to drop/set master, iff it is/was master at a given point * in time. * * Note: DROP_MASTER cannot be free for all, as an arbitrator user could: * - DoS/crash the arbitrator - details would be implementation specific * - open the node, become master implicitly and cause issues * * As a result this fixes the following when using root-less build w/o logind * - startx * - weston * - various compositors based on wlroots */ static int drm_master_check_perm(struct drm_device *dev, struct drm_file *file_priv) { … } int drm_setmaster_ioctl(struct drm_device *dev, void *data, struct drm_file *file_priv) { … } static void drm_drop_master(struct drm_device *dev, struct drm_file *fpriv) { … } int drm_dropmaster_ioctl(struct drm_device *dev, void *data, struct drm_file *file_priv) { … } int drm_master_open(struct drm_file *file_priv) { … } void drm_master_release(struct drm_file *file_priv) { … } /** * drm_master_get - reference a master pointer * @master: &struct drm_master * * Increments the reference count of @master and returns a pointer to @master. */ struct drm_master *drm_master_get(struct drm_master *master) { … } EXPORT_SYMBOL(…); /** * drm_file_get_master - reference &drm_file.master of @file_priv * @file_priv: DRM file private * * Increments the reference count of @file_priv's &drm_file.master and returns * the &drm_file.master. If @file_priv has no &drm_file.master, returns NULL. * * Master pointers returned from this function should be unreferenced using * drm_master_put(). */ struct drm_master *drm_file_get_master(struct drm_file *file_priv) { … } EXPORT_SYMBOL(…); static void drm_master_destroy(struct kref *kref) { … } /** * drm_master_put - unreference and clear a master pointer * @master: pointer to a pointer of &struct drm_master * * This decrements the &drm_master behind @master and sets it to NULL. */ void drm_master_put(struct drm_master **master) { … } EXPORT_SYMBOL(…); /* Used by drm_client and drm_fb_helper */ bool drm_master_internal_acquire(struct drm_device *dev) { … } EXPORT_SYMBOL(…); /* Used by drm_client and drm_fb_helper */ void drm_master_internal_release(struct drm_device *dev) { … } EXPORT_SYMBOL(…);
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