/*
* 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/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.
*/
static bool drm_is_current_master_locked(struct drm_file *fpriv)
{
lockdep_assert_held_once(&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;
mutex_lock(&fpriv->minor->dev->master_mutex);
ret = drm_is_current_master_locked(fpriv);
mutex_unlock(&fpriv->minor->dev->master_mutex);
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;
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;
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;
}
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)
{
if (file_priv->pid == task_pid(current) && file_priv->was_master)
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;
mutex_lock(&dev->master_mutex);
ret = drm_master_check_perm(dev, file_priv);
if (ret)
goto out_unlock;
if (drm_is_current_master_locked(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_locked(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
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_locked(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_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);
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);
