From: Keith Packard <keithp@keithp.com>
Date: Wed, 20 Dec 2017 22:54:24 -0800
Subject: drm: move lease init after validation in drm_lease_create
Git-commit: d2a48e52541cdf474ef35d51e8d73ded5be33122
Patch-mainline: v4.15-rc5
References: FATE#326289 FATE#326079 FATE#326049 FATE#322398 FATE#326166

Patch bd36d3bab2e3d08f80766c86487090dbceed4651 fixed a deadlock in the
failure path of drm_lease_create. This made the partially initialized
lease object visible for a short window of time.

To avoid having the lessee state appear transiently, I've rearranged
the code so that the lessor fields are not filled in until the
parameters are all validated and the function will succeed.

Signed-off-by: Keith Packard <keithp@keithp.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20171221065424.1304-1-keithp@keithp.com

Acked-by: Petr Tesarik <ptesarik@suse.com>
---
 drivers/gpu/drm/drm_lease.c |   22 +++++++++++-----------
 1 file changed, 11 insertions(+), 11 deletions(-)

--- a/drivers/gpu/drm/drm_lease.c
+++ b/drivers/gpu/drm/drm_lease.c
@@ -220,17 +220,6 @@ static struct drm_master *drm_lease_crea
 
 	mutex_lock(&dev->mode_config.idr_mutex);
 
-	/* Insert the new lessee into the tree */
-	id = idr_alloc(&(drm_lease_owner(lessor)->lessee_idr), lessee, 1, 0, GFP_KERNEL);
-	if (id < 0) {
-		error = id;
-		goto out_lessee;
-	}
-
-	lessee->lessee_id = id;
-	lessee->lessor = drm_master_get(lessor);
-	list_add_tail(&lessee->lessee_list, &lessor->lessees);
-
 	idr_for_each_entry(leases, entry, object) {
 		error = 0;
 		if (!idr_find(&dev->mode_config.crtc_idr, object))
@@ -246,6 +235,17 @@ static struct drm_master *drm_lease_crea
 		}
 	}
 
+	/* Insert the new lessee into the tree */
+	id = idr_alloc(&(drm_lease_owner(lessor)->lessee_idr), lessee, 1, 0, GFP_KERNEL);
+	if (id < 0) {
+		error = id;
+		goto out_lessee;
+	}
+
+	lessee->lessee_id = id;
+	lessee->lessor = drm_master_get(lessor);
+	list_add_tail(&lessee->lessee_list, &lessor->lessees);
+
 	/* Move the leases over */
 	lessee->leases = *leases;
 	DRM_DEBUG_LEASE("new lessee %d %p, lessor %d %p\n", lessee->lessee_id, lessee, lessor->lessee_id, lessor);