dist/drm/drm_auth.c

/*        $NetBSD: drm_auth.c,v 1.6 2021/12/19 12:30:04 riastradh Exp $         */

/*
 * 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 <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: drm_auth.c,v 1.6 2021/12/19 12:30:04 riastradh Exp $");

#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"
#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;

          idr_preload(GFP_KERNEL);
          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);
          idr_preload_end();

          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 int drm_set_master(struct drm_device *dev, struct drm_file *fpriv,
                                bool new_master)
{
          int ret = 0;

          dev->master = drm_master_get(fpriv->master);
          if (dev->driver->master_set) {
                    ret = dev->driver->master_set(dev, fpriv, new_master);
                    if (unlikely(ret != 0)) {
                              drm_master_put(&dev->master);
                    }
          }

          return ret;
}

static int drm_new_set_master(struct drm_device *dev, struct drm_file *fpriv)
{
          struct drm_master *old_master;
          int ret;

          lockdep_assert_held_once(&dev->master_mutex);

          WARN_ON(fpriv->is_master);
          old_master = fpriv->master;
          fpriv->master = drm_master_create(dev);
          if (!fpriv->master) {
                    fpriv->master = old_master;
                    return -ENOMEM;
          }

          if (dev->driver->master_create) {
                    ret = dev->driver->master_create(dev, fpriv->master);
                    if (ret)
                              goto out_err;
          }
          fpriv->is_master = 1;
          fpriv->authenticated = 1;

          ret = drm_set_master(dev, fpriv, true);
          if (ret)
                    goto out_err;

          if (old_master)
                    drm_master_put(&old_master);

          return 0;

out_err:
          /* drop references and restore old master on failure */
          drm_master_put(&fpriv->master);
          fpriv->master = old_master;
          fpriv->is_master = 0;

          return ret;
}

int drm_setmaster_ioctl(struct drm_device *dev, void *data,
                              struct drm_file *file_priv)
{
          int ret = 0;

          mutex_lock(&dev->master_mutex);
          if (drm_is_current_master(file_priv))
                    goto out_unlock;

          if (dev->master) {
                    ret = -EINVAL;
                    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;
          }

          ret = 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 = -EINVAL;

          mutex_lock(&dev->master_mutex);
          if (!drm_is_current_master(file_priv))
                    goto out_unlock;

          if (!dev->master)
                    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;
          }

          ret = 0;
          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
                    file_priv->master = drm_master_get(dev->master);
          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 = file_priv->master;

          mutex_lock(&dev->master_mutex);
          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)
{
          return fpriv->is_master && drm_lease_owner(fpriv->master) == fpriv->minor->dev->master;
}
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);

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);

          if (dev->driver->master_destroy)
                    dev->driver->master_destroy(dev, master);

          drm_legacy_master_rmmaps(dev, master);

          idr_destroy(&master->magic_map);
          idr_destroy(&master->leases);
          idr_destroy(&master->lessee_idr);

#ifdef CONFIG_DRM_LEGACY
          /* XXX drm_master_legacy_init unwind */
          DRM_DESTROY_WAITQUEUE(&master->lock.lock_queue);
          spin_lock_destroy(&master->lock.spinlock);
#endif

          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);