From 22a07038c0eaf4d1315a493ce66dcd255accba19 Mon Sep 17 00:00:00 2001
From: Joe Moriarty <joe.moriarty@oracle.com>
Date: Mon, 12 Feb 2018 14:51:42 -0500
Subject: drm: NULL pointer dereference [null-pointer-deref] (CWE 476) problem
Git-commit: 22a07038c0eaf4d1315a493ce66dcd255accba19
Patch-mainline: v4.17-rc1
References: FATE#326289 FATE#326079 FATE#326049 FATE#322398 FATE#326166
  bsc#1114279

The Parfait (version 2.1.0) static code analysis tool found the
following NULL pointer derefernce problem.

- drivers/gpu/drm/drm_dp_mst_topology.c
The call to drm_dp_calculate_rad() in function drm_dp_port_setup_pdt()
could result in a NULL pointer being returned to port->mstb due to a
failure to allocate memory for port->mstb.

Signed-off-by: Joe Moriarty <joe.moriarty@oracle.com>
Reviewed-by: Steven Sistare <steven.sistare@oracle.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20180212195144.98323-3-joe.moriarty@oracle.com
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
---
 drivers/gpu/drm/drm_dp_mst_topology.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index 36df7df5fe1a0c..6fac4129e6a258 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -1082,10 +1082,12 @@ static bool drm_dp_port_setup_pdt(struct drm_dp_mst_port *port)
 		lct = drm_dp_calculate_rad(port, rad);
 
 		port->mstb = drm_dp_add_mst_branch_device(lct, rad);
-		port->mstb->mgr = port->mgr;
-		port->mstb->port_parent = port;
+		if (port->mstb) {
+			port->mstb->mgr = port->mgr;
+			port->mstb->port_parent = port;
 
-		send_link = true;
+			send_link = true;
+		}
 		break;
 	}
 	return send_link;
-- 
2.26.0