FAILED: patch "[PATCH] drm: fix drm_dp_mst_port refcount leaks in" failed to apply to 4.14-stable tree

The patch below does not apply to the 4.14-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From a34a0a632dd991a371fec56431d73279f9c54029 Mon Sep 17 00:00:00 2001
From: Xin Xiong <[email protected]>
Date: Sun, 19 Jul 2020 23:45:45 +0800
Subject: [PATCH] drm: fix drm_dp_mst_port refcount leaks in
drm_dp_mst_allocate_vcpi
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drm_dp_mst_allocate_vcpi() invokes drm_dp_mst_topology_get_port_validated(), which increases the refcount of the "port".

These reference counting issues take place in two exception handling paths separately. Either when “slots” is less than 0 or when drm_dp_init_vcpi() returns a negative value, the function forgets to reduce the refcnt increased drm_dp_mst_topology_get_port_validated(), which results in a refcount leak.

Fix these issues by pulling up the error handling when "slots" is less than 0, and calling drm_dp_mst_topology_put_port() before termination when drm_dp_init_vcpi() returns a negative value.

index 09b32289497e..b23cb2fec3f3 100644
@@ -4308,11 +4308,11 @@ bool drm_dp_mst_allocate_vcpi(struct drm_dp_mst_topology_mgr *mgr,
 {
 	int ret;
 
-	port = drm_dp_mst_topology_get_port_validated(mgr, port);
-	if (!port)
+	if (slots < 0)
 		return false;
 
-	if (slots < 0)
+	port = drm_dp_mst_topology_get_port_validated(mgr, port);
+	if (!port)
 		return false;
 
 	if (port->vcpi.vcpi > 0) {

@@ -4328,6 +4328,7 @@ bool drm_dp_mst_allocate_vcpi(struct drm_dp_mst_topology_mgr *mgr,
 	if (ret) {
 		DRM_DEBUG_KMS("failed to init vcpi slots=%d max=63 ret=%d\n",
 			      DIV_ROUND_UP(pbn, mgr->pbn_div), ret);
+		drm_dp_mst_topology_put_port(port);
 		goto out;
 	}
 	DRM_DEBUG_KMS("initing vcpi for pbn=%d slots=%d\n",