From: Keith Packard <keithp@keithp.com>
Date: Fri, 19 Jan 2018 01:51:59 +0000 (-0800)
Subject: drm: Check for lessee in DROP_MASTER ioctl
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=761e05a702f5d537ffcca1ba933f9f0a968aa022;p=linux.git

drm: Check for lessee in DROP_MASTER ioctl

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.

Signed-off-by: Keith Packard <keithp@keithp.com>
Fixes: 2ed077e467ee ("drm: Add drm_object lease infrastructure [v5]")
Cc: <stable@vger.kernel.org> # v4.15+
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20180119015159.1606-1-keithp@keithp.com
---

diff --git a/drivers/gpu/drm/drm_auth.c b/drivers/gpu/drm/drm_auth.c
index aad468d170a7e..d9c0f75739054 100644
--- a/drivers/gpu/drm/drm_auth.c
+++ b/drivers/gpu/drm/drm_auth.c
@@ -230,6 +230,12 @@ int drm_dropmaster_ioctl(struct drm_device *dev, void *data,
 	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: