[PATCH 4.19 34/45] drm: Reorder set_property_atomic to avoid returning with an active ww_ctx

[Greg Kroah-Hartman]

4.19-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>

commit 227ad6d957898a88b1746e30234ece64d305f066 upstream.

Delay the drm_modeset_acquire_init() until after we check for an
allocation failure so that we can return immediately upon error without
having to unwind.

WARNING: lock held when returning to user space!
4.20.0+ #174 Not tainted
------------------------------------------------
syz-executor556/8153 is leaving the kernel with locks still held!
1 lock held by syz-executor556/8153:
  #0: 000000005100c85c (crtc_ww_class_acquire){+.+.}, at:
set_property_atomic+0xb3/0x330 drivers/gpu/drm/drm_mode_object.c:462

Reported-by: syzbot+6ea337c427f5083ebdf2@xxxxxxxxxxxxxxxxxxxxxxxxx
Fixes: 144a7999d633 ("drm: Handle properties in the core for atomic drivers")
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
Cc: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx>
Cc: Sean Paul <sean@xxxxxxxxxx>
Cc: David Airlie <airlied@xxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> # v4.14+
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx>
Link: https://patchwork.freedesktop.org/patch/msgid/20181230122842.21917-1-chris@xxxxxxxxxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/gpu/drm/drm_mode_object.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- a/drivers/gpu/drm/drm_mode_object.c
+++ b/drivers/gpu/drm/drm_mode_object.c
@@ -458,12 +458,13 @@ static int set_property_atomic(struct dr
 	struct drm_modeset_acquire_ctx ctx;
 	int ret;
 
-	drm_modeset_acquire_init(&ctx, 0);
-
 	state = drm_atomic_state_alloc(dev);
 	if (!state)
 		return -ENOMEM;
+
+	drm_modeset_acquire_init(&ctx, 0);
 	state->acquire_ctx = &ctx;
+
 retry:
 	if (prop == state->dev->mode_config.dpms_property) {
 		if (obj->type != DRM_MODE_OBJECT_CONNECTOR) {