diff options
Diffstat (limited to 'drivers/gpu/drm/drm_auth.c')
| -rw-r--r-- | drivers/gpu/drm/drm_auth.c | 494 |
1 files changed, 375 insertions, 119 deletions
diff --git a/drivers/gpu/drm/drm_auth.c b/drivers/gpu/drm/drm_auth.c index 3cedae12b3c1..a2556d16bed6 100644 --- a/drivers/gpu/drm/drm_auth.c +++ b/drivers/gpu/drm/drm_auth.c @@ -1,11 +1,3 @@ -/** - * \file drm_auth.c - * IOCTLs for authentication - * - * \author Rickard E. (Rik) Faith <faith@valinux.com> - * \author Gareth Hughes <gareth@valinux.com> - */ - /* * Created: Tue Feb 2 08:37:54 1999 by faith@valinux.com * @@ -13,6 +5,9 @@ * 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 @@ -33,162 +28,423 @@ * OTHER DEALINGS IN THE SOFTWARE. */ -#include <drm/drmP.h> +#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" /** - * Find the file with the given magic number. + * DOC: master and authentication * - * \param dev DRM device. - * \param magic magic number. + * &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. * - * Searches in drm_device::magiclist within all files with the same hash key - * the one with matching magic number, while holding the drm_device::struct_mutex - * lock. + * 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 struct drm_file *drm_find_file(struct drm_master *master, drm_magic_t magic) + +static bool drm_is_current_master_locked(struct drm_file *fpriv) { - struct drm_file *retval = NULL; - struct drm_magic_entry *pt; - struct drm_hash_item *hash; - struct drm_device *dev = master->minor->dev; + lockdep_assert_once(lockdep_is_held(&fpriv->master_lookup_lock) || + lockdep_is_held(&fpriv->minor->dev->master_mutex)); - mutex_lock(&dev->struct_mutex); - if (!drm_ht_find_item(&master->magiclist, (unsigned long)magic, &hash)) { - pt = drm_hash_entry(hash, struct drm_magic_entry, hash_item); - retval = pt->priv; - } - mutex_unlock(&dev->struct_mutex); - return retval; + return fpriv->is_master && drm_lease_owner(fpriv->master) == fpriv->minor->dev->master; } /** - * Adds a magic number. + * drm_is_current_master - checks whether @priv is the current master + * @fpriv: DRM file private * - * \param dev DRM device. - * \param priv file private data. - * \param magic magic number. + * Checks whether @fpriv is current master on its device. This decides whether a + * client is allowed to run DRM_MASTER IOCTLs. * - * Creates a drm_magic_entry structure and appends to the linked list - * associated the magic number hash key in drm_device::magiclist, while holding - * the drm_device::struct_mutex lock. + * 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. */ -static int drm_add_magic(struct drm_master *master, struct drm_file *priv, - drm_magic_t magic) +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(sizeof(*master), GFP_KERNEL); + 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) { - struct drm_magic_entry *entry; - struct drm_device *dev = master->minor->dev; - DRM_DEBUG("%d\n", magic); + dev->master = drm_master_get(fpriv->master); + if (dev->driver->master_set) + dev->driver->master_set(dev, fpriv, new_master); - entry = kzalloc(sizeof(*entry), GFP_KERNEL); - if (!entry) + 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; - entry->priv = priv; - entry->hash_item.key = (unsigned long)magic; - mutex_lock(&dev->struct_mutex); - drm_ht_insert_item(&master->magiclist, &entry->hash_item); - list_add_tail(&entry->head, &master->magicfree); - mutex_unlock(&dev->struct_mutex); + 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; } -/** - * Remove a magic number. +/* + * 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. + * * - * \param dev DRM device. - * \param magic magic number. + * 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. * - * Searches and unlinks the entry in drm_device::magiclist with the magic - * number hash key, while holding the drm_device::struct_mutex lock. + * 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 */ -int drm_remove_magic(struct drm_master *master, drm_magic_t magic) +static int +drm_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) { - struct drm_magic_entry *pt; - struct drm_hash_item *hash; - struct drm_device *dev = master->minor->dev; + int ret; - DRM_DEBUG("%d\n", magic); + guard(mutex)(&dev->master_mutex); - mutex_lock(&dev->struct_mutex); - if (drm_ht_find_item(&master->magiclist, (unsigned long)magic, &hash)) { - mutex_unlock(&dev->struct_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; } - pt = drm_hash_entry(hash, struct drm_magic_entry, hash_item); - drm_ht_remove_item(&master->magiclist, hash); - list_del(&pt->head); - mutex_unlock(&dev->struct_mutex); - kfree(pt); + drm_set_master(dev, file_priv, false); - return 0; + return ret; } -/** - * Get a unique magic number (ioctl). - * - * \param inode device inode. - * \param file_priv DRM file private. - * \param cmd command. - * \param arg pointer to a resulting drm_auth structure. - * \return zero on success, or a negative number on failure. - * - * If there is a magic number in drm_file::magic then use it, otherwise - * searches an unique non-zero magic number and add it associating it with \p - * file_priv. - * This ioctl needs protection by the drm_global_mutex, which protects - * struct drm_file::magic and struct drm_magic_entry::priv. - */ -int drm_getmagic(struct drm_device *dev, void *data, struct drm_file *file_priv) +static void drm_drop_master(struct drm_device *dev, + struct drm_file *fpriv) { - static drm_magic_t sequence = 0; - static DEFINE_SPINLOCK(lock); - struct drm_auth *auth = data; + 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; +} - /* Find unique magic */ - if (file_priv->magic) { - auth->magic = file_priv->magic; +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 { - do { - spin_lock(&lock); - if (!sequence) - ++sequence; /* reserve 0 */ - auth->magic = sequence++; - spin_unlock(&lock); - } while (drm_find_file(file_priv->master, auth->magic)); - file_priv->magic = auth->magic; - drm_add_magic(file_priv->master, file_priv, auth->magic); + spin_lock(&file_priv->master_lookup_lock); + file_priv->master = drm_master_get(dev->master); + spin_unlock(&file_priv->master_lookup_lock); } - DRM_DEBUG("%u\n", auth->magic); + return ret; +} - return 0; +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 == 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); } /** - * Authenticate with a magic. + * drm_master_get - reference a master pointer + * @master: &struct drm_master * - * \param inode device inode. - * \param file_priv DRM file private. - * \param cmd command. - * \param arg pointer to a drm_auth structure. - * \return zero if authentication successed, or a negative number otherwise. + * 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 * - * Checks if \p file_priv is associated with the magic number passed in \arg. - * This ioctl needs protection by the drm_global_mutex, which protects - * struct drm_file::magic and struct drm_magic_entry::priv. + * 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(). */ -int drm_authmagic(struct drm_device *dev, void *data, - struct drm_file *file_priv) +struct drm_master *drm_file_get_master(struct drm_file *file_priv) { - struct drm_auth *auth = data; - struct drm_file *file; + struct drm_master *master = NULL; - DRM_DEBUG("%u\n", auth->magic); - if ((file = drm_find_file(file_priv->master, auth->magic))) { - file->authenticated = 1; - drm_remove_magic(file_priv->master, auth->magic); - return 0; + 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 -EINVAL; + + 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); |