439 lines
12 KiB
C
439 lines
12 KiB
C
/*
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* Created: Tue Feb 2 08:37:54 1999 by faith@valinux.com
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*
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* Copyright 1999 Precision Insight, Inc., Cedar Park, Texas.
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* Copyright 2000 VA Linux Systems, Inc., Sunnyvale, California.
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* All Rights Reserved.
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*
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* Author Rickard E. (Rik) Faith <faith@valinux.com>
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* Author Gareth Hughes <gareth@valinux.com>
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*
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* Permission is hereby granted, free of charge, to any person obtaining a
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* copy of this software and associated documentation files (the "Software"),
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* to deal in the Software without restriction, including without limitation
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* the rights to use, copy, modify, merge, publish, distribute, sublicense,
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* and/or sell copies of the Software, and to permit persons to whom the
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* Software is furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice (including the next
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* paragraph) shall be included in all copies or substantial portions of the
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* Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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* VA LINUX SYSTEMS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
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* OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
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* ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
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* OTHER DEALINGS IN THE SOFTWARE.
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*/
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#include <linux/slab.h>
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#include <drm/drm_auth.h>
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#include <drm/drm_drv.h>
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#include <drm/drm_file.h>
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#include <drm/drm_lease.h>
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#include <drm/drm_print.h>
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#include "drm_internal.h"
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#include "drm_legacy.h"
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/**
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* DOC: master and authentication
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*
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* &struct drm_master is used to track groups of clients with open
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* primary/legacy device nodes. For every &struct drm_file which has had at
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* least once successfully became the device master (either through the
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* SET_MASTER IOCTL, or implicitly through opening the primary device node when
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* no one else is the current master that time) there exists one &drm_master.
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* This is noted in &drm_file.is_master. All other clients have just a pointer
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* to the &drm_master they are associated with.
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*
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* In addition only one &drm_master can be the current master for a &drm_device.
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* It can be switched through the DROP_MASTER and SET_MASTER IOCTL, or
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* implicitly through closing/openeing the primary device node. See also
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* drm_is_current_master().
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*
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* Clients can authenticate against the current master (if it matches their own)
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* using the GETMAGIC and AUTHMAGIC IOCTLs. Together with exchanging masters,
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* this allows controlled access to the device for an entire group of mutually
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* trusted clients.
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*/
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int drm_getmagic(struct drm_device *dev, void *data, struct drm_file *file_priv)
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{
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struct drm_auth *auth = data;
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int ret = 0;
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mutex_lock(&dev->master_mutex);
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if (!file_priv->magic) {
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ret = idr_alloc(&file_priv->master->magic_map, file_priv,
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1, 0, GFP_KERNEL);
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if (ret >= 0)
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file_priv->magic = ret;
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}
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auth->magic = file_priv->magic;
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mutex_unlock(&dev->master_mutex);
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DRM_DEBUG("%u\n", auth->magic);
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return ret < 0 ? ret : 0;
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}
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int drm_authmagic(struct drm_device *dev, void *data,
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struct drm_file *file_priv)
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{
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struct drm_auth *auth = data;
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struct drm_file *file;
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DRM_DEBUG("%u\n", auth->magic);
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mutex_lock(&dev->master_mutex);
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file = idr_find(&file_priv->master->magic_map, auth->magic);
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if (file) {
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file->authenticated = 1;
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idr_replace(&file_priv->master->magic_map, NULL, auth->magic);
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}
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mutex_unlock(&dev->master_mutex);
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return file ? 0 : -EINVAL;
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}
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struct drm_master *drm_master_create(struct drm_device *dev)
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{
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struct drm_master *master;
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master = kzalloc(sizeof(*master), GFP_KERNEL);
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if (!master)
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return NULL;
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kref_init(&master->refcount);
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drm_master_legacy_init(master);
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idr_init(&master->magic_map);
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master->dev = dev;
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/* initialize the tree of output resource lessees */
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INIT_LIST_HEAD(&master->lessees);
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INIT_LIST_HEAD(&master->lessee_list);
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idr_init(&master->leases);
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idr_init(&master->lessee_idr);
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return master;
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}
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static int drm_set_master(struct drm_device *dev, struct drm_file *fpriv,
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bool new_master)
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{
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int ret = 0;
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dev->master = drm_master_get(fpriv->master);
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if (dev->driver->master_set) {
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ret = dev->driver->master_set(dev, fpriv, new_master);
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if (unlikely(ret != 0)) {
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drm_master_put(&dev->master);
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}
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}
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fpriv->was_master = (ret == 0);
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return ret;
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}
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static int drm_new_set_master(struct drm_device *dev, struct drm_file *fpriv)
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{
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struct drm_master *old_master;
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int ret;
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lockdep_assert_held_once(&dev->master_mutex);
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WARN_ON(fpriv->is_master);
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old_master = fpriv->master;
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fpriv->master = drm_master_create(dev);
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if (!fpriv->master) {
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fpriv->master = old_master;
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return -ENOMEM;
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}
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fpriv->is_master = 1;
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fpriv->authenticated = 1;
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ret = drm_set_master(dev, fpriv, true);
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if (ret)
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goto out_err;
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if (old_master)
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drm_master_put(&old_master);
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return 0;
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out_err:
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/* drop references and restore old master on failure */
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drm_master_put(&fpriv->master);
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fpriv->master = old_master;
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fpriv->is_master = 0;
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return ret;
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}
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/*
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* In the olden days the SET/DROP_MASTER ioctls used to return EACCES when
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* CAP_SYS_ADMIN was not set. This was used to prevent rogue applications
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* from becoming master and/or failing to release it.
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*
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* At the same time, the first client (for a given VT) is _always_ master.
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* Thus in order for the ioctls to succeed, one had to _explicitly_ run the
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* application as root or flip the setuid bit.
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*
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* If the CAP_SYS_ADMIN was missing, no other client could become master...
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* EVER :-( Leading to a) the graphics session dying badly or b) a completely
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* locked session.
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*
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*
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* As some point systemd-logind was introduced to orchestrate and delegate
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* master as applicable. It does so by opening the fd and passing it to users
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* while in itself logind a) does the set/drop master per users' request and
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* b) * implicitly drops master on VT switch.
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*
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* Even though logind looks like the future, there are a few issues:
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* - some platforms don't have equivalent (Android, CrOS, some BSDs) so
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* root is required _solely_ for SET/DROP MASTER.
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* - applications may not be updated to use it,
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* - any client which fails to drop master* can DoS the application using
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* logind, to a varying degree.
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*
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* * Either due missing CAP_SYS_ADMIN or simply not calling DROP_MASTER.
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*
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*
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* Here we implement the next best thing:
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* - ensure the logind style of fd passing works unchanged, and
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* - allow a client to drop/set master, iff it is/was master at a given point
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* in time.
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*
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* Note: DROP_MASTER cannot be free for all, as an arbitrator user could:
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* - DoS/crash the arbitrator - details would be implementation specific
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* - open the node, become master implicitly and cause issues
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*
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* As a result this fixes the following when using root-less build w/o logind
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* - startx
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* - weston
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* - various compositors based on wlroots
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*/
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static int
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drm_master_check_perm(struct drm_device *dev, struct drm_file *file_priv)
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{
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if (file_priv->pid == task_pid(current) && file_priv->was_master)
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return 0;
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if (!capable(CAP_SYS_ADMIN))
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return -EACCES;
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return 0;
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}
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int drm_setmaster_ioctl(struct drm_device *dev, void *data,
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struct drm_file *file_priv)
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{
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int ret = 0;
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mutex_lock(&dev->master_mutex);
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ret = drm_master_check_perm(dev, file_priv);
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if (ret)
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goto out_unlock;
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if (drm_is_current_master(file_priv))
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goto out_unlock;
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if (dev->master) {
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ret = -EBUSY;
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goto out_unlock;
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}
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if (!file_priv->master) {
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ret = -EINVAL;
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goto out_unlock;
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}
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if (!file_priv->is_master) {
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ret = drm_new_set_master(dev, file_priv);
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goto out_unlock;
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}
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if (file_priv->master->lessor != NULL) {
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DRM_DEBUG_LEASE("Attempt to set lessee %d as master\n", file_priv->master->lessee_id);
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ret = -EINVAL;
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goto out_unlock;
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}
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ret = drm_set_master(dev, file_priv, false);
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out_unlock:
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mutex_unlock(&dev->master_mutex);
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return ret;
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}
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static void drm_drop_master(struct drm_device *dev,
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struct drm_file *fpriv)
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{
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if (dev->driver->master_drop)
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dev->driver->master_drop(dev, fpriv);
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drm_master_put(&dev->master);
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}
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int drm_dropmaster_ioctl(struct drm_device *dev, void *data,
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struct drm_file *file_priv)
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{
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int ret = -EINVAL;
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mutex_lock(&dev->master_mutex);
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ret = drm_master_check_perm(dev, file_priv);
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if (ret)
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goto out_unlock;
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ret = -EINVAL;
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if (!drm_is_current_master(file_priv))
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goto out_unlock;
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if (!dev->master)
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goto out_unlock;
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if (file_priv->master->lessor != NULL) {
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DRM_DEBUG_LEASE("Attempt to drop lessee %d as master\n", file_priv->master->lessee_id);
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ret = -EINVAL;
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goto out_unlock;
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}
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ret = 0;
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drm_drop_master(dev, file_priv);
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out_unlock:
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mutex_unlock(&dev->master_mutex);
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return ret;
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}
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int drm_master_open(struct drm_file *file_priv)
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{
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struct drm_device *dev = file_priv->minor->dev;
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int ret = 0;
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/* if there is no current master make this fd it, but do not create
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* any master object for render clients */
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mutex_lock(&dev->master_mutex);
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if (!dev->master)
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ret = drm_new_set_master(dev, file_priv);
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else
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file_priv->master = drm_master_get(dev->master);
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mutex_unlock(&dev->master_mutex);
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return ret;
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}
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void drm_master_release(struct drm_file *file_priv)
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{
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struct drm_device *dev = file_priv->minor->dev;
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struct drm_master *master = file_priv->master;
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mutex_lock(&dev->master_mutex);
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if (file_priv->magic)
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idr_remove(&file_priv->master->magic_map, file_priv->magic);
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if (!drm_is_current_master(file_priv))
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goto out;
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drm_legacy_lock_master_cleanup(dev, master);
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if (dev->master == file_priv->master)
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drm_drop_master(dev, file_priv);
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out:
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if (drm_core_check_feature(dev, DRIVER_MODESET) && file_priv->is_master) {
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/* Revoke any leases held by this or lessees, but only if
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* this is the "real" master
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*/
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drm_lease_revoke(master);
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}
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/* drop the master reference held by the file priv */
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if (file_priv->master)
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drm_master_put(&file_priv->master);
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mutex_unlock(&dev->master_mutex);
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}
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/**
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* drm_is_current_master - checks whether @priv is the current master
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* @fpriv: DRM file private
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*
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* Checks whether @fpriv is current master on its device. This decides whether a
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* client is allowed to run DRM_MASTER IOCTLs.
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*
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* Most of the modern IOCTL which require DRM_MASTER are for kernel modesetting
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* - the current master is assumed to own the non-shareable display hardware.
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*/
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bool drm_is_current_master(struct drm_file *fpriv)
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{
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return fpriv->is_master && drm_lease_owner(fpriv->master) == fpriv->minor->dev->master;
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}
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EXPORT_SYMBOL(drm_is_current_master);
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/**
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* drm_master_get - reference a master pointer
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* @master: &struct drm_master
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*
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* Increments the reference count of @master and returns a pointer to @master.
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*/
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struct drm_master *drm_master_get(struct drm_master *master)
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{
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kref_get(&master->refcount);
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return master;
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}
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EXPORT_SYMBOL(drm_master_get);
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static void drm_master_destroy(struct kref *kref)
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{
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struct drm_master *master = container_of(kref, struct drm_master, refcount);
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struct drm_device *dev = master->dev;
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if (drm_core_check_feature(dev, DRIVER_MODESET))
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drm_lease_destroy(master);
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drm_legacy_master_rmmaps(dev, master);
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idr_destroy(&master->magic_map);
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idr_destroy(&master->leases);
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idr_destroy(&master->lessee_idr);
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kfree(master->unique);
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kfree(master);
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}
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/**
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* drm_master_put - unreference and clear a master pointer
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* @master: pointer to a pointer of &struct drm_master
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*
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* This decrements the &drm_master behind @master and sets it to NULL.
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*/
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void drm_master_put(struct drm_master **master)
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{
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kref_put(&(*master)->refcount, drm_master_destroy);
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*master = NULL;
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}
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EXPORT_SYMBOL(drm_master_put);
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/* Used by drm_client and drm_fb_helper */
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bool drm_master_internal_acquire(struct drm_device *dev)
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{
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mutex_lock(&dev->master_mutex);
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if (dev->master) {
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mutex_unlock(&dev->master_mutex);
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return false;
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}
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return true;
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}
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EXPORT_SYMBOL(drm_master_internal_acquire);
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/* Used by drm_client and drm_fb_helper */
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void drm_master_internal_release(struct drm_device *dev)
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{
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mutex_unlock(&dev->master_mutex);
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}
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EXPORT_SYMBOL(drm_master_internal_release);
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