/* * 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 <faith@valinux.com> * Author Gareth Hughes <gareth@valinux.com> * * 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/export.h>#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){	lockdep_assert_once(lockdep_is_held(&fpriv->master_lookup_lock) ||			    lockdep_is_held(&fpriv->minor->dev->master_mutex)); 	return fpriv->is_master && drm_lease_owner(fpriv->master) == fpriv->minor->dev->master;} /** * 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){	bool ret; 	spin_lock(&fpriv->master_lookup_lock);	ret = drm_is_current_master_locked(fpriv);	spin_unlock(&fpriv->master_lookup_lock); 	return ret;}EXPORT_SYMBOL(drm_is_current_master); int drm_getmagic(struct drm_device *dev, void *data, struct drm_file *file_priv){	struct drm_auth *auth = data;	int ret = 0; 	guard(mutex)(&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; 	drm_dbg_core(dev, "%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_dbg_core(dev, "%u\n", auth->magic); 	guard(mutex)(&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);	} 	return file ? 0 : -EINVAL;} struct drm_master *drm_master_create(struct drm_device *dev){	struct drm_master *master; 	master = kzalloc_obj(*master);	if (!master)		return NULL; 	kref_init(&master->refcount);	idr_init_base(&master->magic_map, 1);	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_base(&master->lessee_idr, 1); 	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 intdrm_master_check_perm(struct drm_device *dev, struct drm_file *file_priv){	if (file_priv->was_master &&	    rcu_access_pointer(file_priv->pid) == task_tgid(current))		return 0; 	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; 	guard(mutex)(&dev->master_mutex); 	ret = drm_master_check_perm(dev, file_priv);	if (ret)		return ret; 	if (drm_is_current_master_locked(file_priv))		return ret; 	if (dev->master)		return -EBUSY; 	if (!file_priv->master)		return -EINVAL; 	if (!file_priv->is_master)		return drm_new_set_master(dev, file_priv); 	if (file_priv->master->lessor != NULL) {		drm_dbg_lease(dev,			      "Attempt to set lessee %d as master\n",			      file_priv->master->lessee_id);		return -EINVAL;	} 	drm_set_master(dev, file_priv, false); 	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; 	guard(mutex)(&dev->master_mutex); 	ret = drm_master_check_perm(dev, file_priv);	if (ret)		return ret; 	if (!drm_is_current_master_locked(file_priv))		return -EINVAL; 	if (!dev->master)		return -EINVAL; 	if (file_priv->master->lessor != NULL) {		drm_dbg_lease(dev,			      "Attempt to drop lessee %d as master\n",			      file_priv->master->lessee_id);		return -EINVAL;	} 	drm_drop_master(dev, file_priv); 	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	 */	guard(mutex)(&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);	} 	return ret;} void drm_master_release(struct drm_file *file_priv){	struct drm_device *dev = file_priv->minor->dev;	struct drm_master *master; 	guard(mutex)(&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_locked(file_priv))		goto out; 	if (dev->master && 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);} /** * 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); 	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);