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drm: don't de-authenticate clients on master-close 

If an active DRM-Master closes its device, we deauthenticate all clients
on that master. However, if an inactive DRM-Master closes its device, we
do nothing. This is quite inconsistent and breaks several scenarios:

 1) If this was used as security mechanism, it fails horribly if a master
    closes a device while VT switched away. Furthermore, none of the few
    drivers using ->master_*() callbacks seems to require it, anyway.

 2) If you spawn weston (or any other non-UMS compositor) in background
    while another compositor is active, both will get assigned to the
    same "drm_master" object. If the foreground compositor now exits, all
    clients of both the foreground AND background compositor will be
    de-authenticated leading to unexpected behavior.

Stop this non-sense and keep clients authenticated. We don't do this when
dropping DRM-Master (i.e., switching VTs) so don't do it on active-close
either!

Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: David Herrmann <dh.herrmann@gmail.com>
This commit is contained in:
David Herrmann 2014-07-22 17:12:26 +02:00
parent 48ba813701
commit 3cb01a9804
2 changed files with 2 additions and 12 deletions
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13
drivers/gpu/drm/drm_fops.c
View File

@ -199,8 +199,7 @@ static int drm_open_helper(struct file *filp, struct drm_minor *minor)
priv->minor = minor;
/* for compatibility root is always authenticated */
priv->always_authenticated = capable(CAP_SYS_ADMIN);
priv->authenticated = priv->always_authenticated;
priv->authenticated = capable(CAP_SYS_ADMIN);
priv->lock_count = 0;
INIT_LIST_HEAD(&priv->lhead);
@ -462,20 +461,12 @@ int drm_release(struct inode *inode, struct file *filp)
if (drm_is_master(file_priv)) {
struct drm_master *master = file_priv->master;
struct drm_file *temp;
mutex_lock(&dev->struct_mutex);
list_for_each_entry(temp, &dev->filelist, lhead) {
if ((temp->master == file_priv->master) &&
(temp != file_priv))
temp->authenticated = temp->always_authenticated;
}
/**
* Since the master is disappearing, so is the
* possibility to lock.
*/
mutex_lock(&dev->struct_mutex);
if (master->lock.hw_lock) {
if (dev->sigdata.lock == master->lock.hw_lock)
dev->sigdata.lock = NULL;

1
include/drm/drmP.h
View File

@ -385,7 +385,6 @@ struct drm_prime_file_private {
/** File private data */
struct drm_file {
unsigned always_authenticated :1;
unsigned authenticated :1;
/* true when the client has asked us to expose stereo 3D mode flags */
unsigned stereo_allowed :1;