Patch "drm: Check for lessee in DROP_MASTER ioctl" has been added to the 4.15-stable tree

This is a note to let you know that I've just added the patch titled

drm: Check for lessee in DROP_MASTER ioctl

to the 4.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
drm-check-for-lessee-in-drop_master-ioctl.patch
and it can be found in the queue-4.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Keith Packard <[email protected]>
Date: Thu, 18 Jan 2018 17:51:59 -0800
Subject: drm: Check for lessee in DROP_MASTER ioctl

From: Keith Packard <[email protected]>

commit 761e05a702f5d537ffcca1ba933f9f0a968aa022 upstream.

Don't let a lessee control what the current DRM master is set to; that's the job of the "real" master. Otherwise, the lessee would disable all access to master operations for the owner and all lessees under it.

This matches the same check made in the SET_MASTER ioctl.

---
 drivers/gpu/drm/drm_auth.c |    6 ++++++
 1 file changed, 6 insertions(+)

@@ -230,6 +230,12 @@ int drm_dropmaster_ioctl(struct drm_devi
 	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:

Patches currently in stable-queue which might be from [email protected] are

queue-4.15/drm-check-for-lessee-in-drop_master-ioctl.patch