From: jsg <jsg@openbsd.org>
Date: Fri, 3 Nov 2023 03:29:36 +0000 (+0000)
Subject: drm/dp_mst: Fix NULL deref in get_mst_branch_device_by_guid_helper()
X-Git-Url: http://artulab.com/gitweb/?a=commitdiff_plain;h=2fb2b219688b2fdf6b8d6da44686f926b105cd58;p=openbsd

drm/dp_mst: Fix NULL deref in get_mst_branch_device_by_guid_helper()

From Lukasz Majczak
6c668e2f338bde76279aeaf4d4c035c4196a479b in linux-6.1.y/6.1.61
3d887d512494d678b17c57b835c32f4e48d34f26 in mainline linux
---

diff --git a/sys/dev/pci/drm/display/drm_dp_mst_topology.c b/sys/dev/pci/drm/display/drm_dp_mst_topology.c
index a0f8b05792a..cb6a61a2525 100644
--- a/sys/dev/pci/drm/display/drm_dp_mst_topology.c
+++ b/sys/dev/pci/drm/display/drm_dp_mst_topology.c
@@ -2584,14 +2584,14 @@ static struct drm_dp_mst_branch *get_mst_branch_device_by_guid_helper(
 	struct drm_dp_mst_branch *found_mstb;
 	struct drm_dp_mst_port *port;
 
+	if (!mstb)
+		return NULL;
+
 	if (memcmp(mstb->guid, guid, 16) == 0)
 		return mstb;
 
 
 	list_for_each_entry(port, &mstb->ports, next) {
-		if (!port->mstb)
-			continue;
-
 		found_mstb = get_mst_branch_device_by_guid_helper(port->mstb, guid);
 
 		if (found_mstb)