drm: Do not drop root privileges for a fancier younger process

When a second process opens the device and master transferrence is
complete, we walk the list of open devices and remove their
authentication. This also revokes our root privilege. Instead of simply
dropping the authentication, this patch reverts the authenticated state
back to its original value.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: David Herrmann <dh.herrmann@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

1 files changed, 3 insertions, 2 deletions

diff --git a/drivers/gpu/drm/drm_fops.c b/drivers/gpu/drm/drm_fops.c
index ee2d330a2fa0..3a7176ce2540 100644
--- a/drivers/gpu/drm/drm_fops.c
+++ b/drivers/gpu/drm/drm_fops.c
@@ -239,7 +239,8 @@ static int drm_open_helper(struct inode *inode, struct file *filp,
 
         priv->ioctl_count = 0;
         /* for compatibility root is always authenticated */
-        priv->authenticated = capable(CAP_SYS_ADMIN);
+        priv->always_authenticated = capable(CAP_SYS_ADMIN);
+        priv->authenticated = priv->always_authenticated;
         priv->lock_count = 0;
 
         INIT_LIST_HEAD(&priv->lhead);
@@ -533,7 +534,7 @@ int drm_release(struct inode *inode, struct file *filp)
                 list_for_each_entry(temp, &dev->filelist, lhead) {
                         if ((temp->master == file_priv->master) &&
                             (temp != file_priv))
-                                temp->authenticated = 0;
+                                temp->authenticated = temp->always_authenticated;
                 }
 
                 /**