/* * Created: Tue Feb 2 08:37:54 1999 by faith@valinux.com * * Copyright 1999 Precision Insight, Inc., Cedar Park, Texas. * Copyright 2000 VA Linux Systems, Inc., Sunnyvale, California. * All Rights Reserved. * * Author Rickard E. (Rik) Faith * Author Gareth Hughes * * 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 #include #include #include #include #include #include "drm_internal.h" #include "drm_legacy.h" /** * DOC: master and authentication * * &struct drm_master is used to track groups of clients with open * primary/legacy 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/openeing 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. */ int drm_getmagic(struct drm_device *dev, void *data, struct drm_file *file_priv) { struct drm_auth *auth = data; int ret = 0; mutex_lock(&dev->master_mutex); if (!file_priv->magic) { ret = idr_alloc(&file_priv->master->magic_map, file_priv, 1, 0, GFP_KERNEL); if (ret >= 0) file_priv->magic = ret; } auth->magic = file_priv->magic; mutex_unlock(&dev->master_mutex); DRM_DEBUG("%u\n", auth->magic); return ret < 0 ? ret : 0; } int drm_authmagic(struct drm_device *dev, void *data, struct drm_file *file_priv) { struct drm_auth *auth = data; struct drm_file *file; DRM_DEBUG("%u\n", auth->magic); mutex_lock(&dev->master_mutex); file = idr_find(&file_priv->master->magic_map, auth->magic); if (file) { file->authenticated = 1; idr_replace(&file_priv->master->magic_map, NULL, auth->magic); } mutex_unlock(&dev->master_mutex); return file ? 0 : -EINVAL; } struct drm_master *drm_master_create(struct drm_device *dev) { struct drm_master *master; master = kzalloc(sizeof(*master), GFP_KERNEL); if (!master) return NULL; kref_init(&master->refcount); drm_master_legacy_init(master); idr_init(&master->magic_map); master->dev = dev; /* initialize the tree of output resource lessees */ INIT_LIST_HEAD(&master->lessees); INIT_LIST_HEAD(&master->lessee_list); idr_init(&master->leases); idr_init(&master->lessee_idr); return master; } static void drm_set_master(struct drm_device *dev, struct drm_file *fpriv, bool new_master) { dev->master = drm_master_get(fpriv->master); if (dev->driver->master_set) dev->driver->master_set(dev, fpriv, new_master); fpriv->was_master = true; } static int drm_new_set_master(struct drm_device *dev, struct drm_file *fpriv) { struct drm_master *old_master; struct drm_master *new_master; lockdep_assert_held_once(&dev->master_mutex); WARN_ON(fpriv->is_master); old_master = fpriv->master; new_master = drm_master_create(dev); if (!new_master) return -ENOMEM; spin_lock(&fpriv->master_lookup_lock); fpriv->master = new_master; spin_unlock(&fpriv->master_lookup_lock); fpriv->is_master = 1; fpriv->authenticated = 1; drm_set_master(dev, fpriv, true); if (old_master) drm_master_put(&old_master); return 0; } /* * 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) { #ifdef __linux__ if (file_priv->pid == task_pid(current) && file_priv->was_master) return 0; #endif if (!capable(CAP_SYS_ADMIN)) return -EACCES; return 0; } int drm_setmaster_ioctl(struct drm_device *dev, void *data, struct drm_file *file_priv) { int ret; mutex_lock(&dev->master_mutex); ret = drm_master_check_perm(dev, file_priv); if (ret) goto out_unlock; if (drm_is_current_master(file_priv)) goto out_unlock; if (dev->master) { ret = -EBUSY; goto out_unlock; } if (!file_priv->master) { ret = -EINVAL; goto out_unlock; } if (!file_priv->is_master) { ret = drm_new_set_master(dev, file_priv); goto out_unlock; } if (file_priv->master->lessor != NULL) { DRM_DEBUG_LEASE("Attempt to set lessee %d as master\n", file_priv->master->lessee_id); ret = -EINVAL; goto out_unlock; } drm_set_master(dev, file_priv, false); out_unlock: mutex_unlock(&dev->master_mutex); return ret; } static void drm_drop_master(struct drm_device *dev, struct drm_file *fpriv) { if (dev->driver->master_drop) dev->driver->master_drop(dev, fpriv); drm_master_put(&dev->master); } int drm_dropmaster_ioctl(struct drm_device *dev, void *data, struct drm_file *file_priv) { int ret; mutex_lock(&dev->master_mutex); ret = drm_master_check_perm(dev, file_priv); if (ret) goto out_unlock; if (!drm_is_current_master(file_priv)) { ret = -EINVAL; goto out_unlock; } if (!dev->master) { ret = -EINVAL; goto out_unlock; } if (file_priv->master->lessor != NULL) { DRM_DEBUG_LEASE("Attempt to drop lessee %d as master\n", file_priv->master->lessee_id); ret = -EINVAL; goto out_unlock; } drm_drop_master(dev, file_priv); out_unlock: mutex_unlock(&dev->master_mutex); return ret; } int drm_master_open(struct drm_file *file_priv) { struct drm_device *dev = file_priv->minor->dev; int ret = 0; /* if there is no current master make this fd it, but do not create * any master object for render clients */ mutex_lock(&dev->master_mutex); if (!dev->master) { ret = drm_new_set_master(dev, file_priv); } else { spin_lock(&file_priv->master_lookup_lock); file_priv->master = drm_master_get(dev->master); spin_unlock(&file_priv->master_lookup_lock); } mutex_unlock(&dev->master_mutex); return ret; } void drm_master_release(struct drm_file *file_priv) { struct drm_device *dev = file_priv->minor->dev; struct drm_master *master; mutex_lock(&dev->master_mutex); master = file_priv->master; if (file_priv->magic) idr_remove(&file_priv->master->magic_map, file_priv->magic); if (!drm_is_current_master(file_priv)) goto out; drm_legacy_lock_master_cleanup(dev, master); if (dev->master == file_priv->master) drm_drop_master(dev, file_priv); out: if (drm_core_check_feature(dev, DRIVER_MODESET) && file_priv->is_master) { /* Revoke any leases held by this or lessees, but only if * this is the "real" master */ drm_lease_revoke(master); } /* drop the master reference held by the file priv */ if (file_priv->master) drm_master_put(&file_priv->master); mutex_unlock(&dev->master_mutex); } /** * 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) { #ifdef notyet return fpriv->is_master && drm_lease_owner(fpriv->master) == fpriv->minor->dev->master; #else return (fpriv->is_master == 1); #endif } EXPORT_SYMBOL(drm_is_current_master); /** * 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) { kref_get(&master->refcount); return master; } EXPORT_SYMBOL(drm_master_get); /** * 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) { struct drm_master *master = NULL; spin_lock(&file_priv->master_lookup_lock); if (!file_priv->master) goto unlock; master = drm_master_get(file_priv->master); unlock: spin_unlock(&file_priv->master_lookup_lock); return master; } EXPORT_SYMBOL(drm_file_get_master); static void drm_master_destroy(struct kref *kref) { struct drm_master *master = container_of(kref, struct drm_master, refcount); struct drm_device *dev = master->dev; if (drm_core_check_feature(dev, DRIVER_MODESET)) drm_lease_destroy(master); drm_legacy_master_rmmaps(dev, master); idr_destroy(&master->magic_map); idr_destroy(&master->leases); idr_destroy(&master->lessee_idr); kfree(master->unique); kfree(master); } /** * 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) { kref_put(&(*master)->refcount, drm_master_destroy); *master = NULL; } EXPORT_SYMBOL(drm_master_put); /* Used by drm_client and drm_fb_helper */ bool drm_master_internal_acquire(struct drm_device *dev) { mutex_lock(&dev->master_mutex); if (dev->master) { mutex_unlock(&dev->master_mutex); return false; } return true; } EXPORT_SYMBOL(drm_master_internal_acquire); /* Used by drm_client and drm_fb_helper */ void drm_master_internal_release(struct drm_device *dev) { mutex_unlock(&dev->master_mutex); } EXPORT_SYMBOL(drm_master_internal_release);