Patch "drm/mst: Avoid dereferencing a NULL mstb in drm_dp_mst_handle_up_req()" has been added to the 4.4-stable tree

Patch "drm/mst: Avoid dereferencing a NULL mstb in drm_dp_mst_handle_up_req()" has been added to the 4.4-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    drm/mst: Avoid dereferencing a NULL mstb in drm_dp_mst_handle_up_req()

to the 4.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     drm-mst-avoid-dereferencing-a-null-mstb-in-drm_dp_mst_handle_up_req.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 7f8b3987da54cb4d41ad2545cd4d7958b9a36bdf Mon Sep 17 00:00:00 2001
From: Imre Deak <imre.deak@intel.com>
Date: Wed, 19 Jul 2017 14:43:29 +0300
Subject: drm/mst: Avoid dereferencing a NULL mstb in drm_dp_mst_handle_up_req()

From: Imre Deak <imre.deak@intel.com>

commit 7f8b3987da54cb4d41ad2545cd4d7958b9a36bdf upstream.

In case of an unknown broadcast message is sent mstb will remain unset,
so check for this.

Cc: Dave Airlie <airlied@redhat.com>
Cc: Lyude <lyude@redhat.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Lyude <lyude@redhat.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20170719114330.26540-3-imre.deak@intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/gpu/drm/drm_dp_mst_topology.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -2323,7 +2323,9 @@ static int drm_dp_mst_handle_up_req(stru
 			DRM_DEBUG_KMS("Got RSN: pn: %d avail_pbn %d\n", msg.u.resource_stat.port_number, msg.u.resource_stat.available_pbn);
 		}
 
-		drm_dp_put_mst_branch_device(mstb);
+		if (mstb)
+			drm_dp_put_mst_branch_device(mstb);
+
 		memset(&mgr->up_req_recv, 0, sizeof(struct drm_dp_sideband_msg_rx));
 	}
 	return ret;


Patches currently in stable-queue which might be from imre.deak@intel.com are

queue-4.4/drm-mst-avoid-dereferencing-a-null-mstb-in-drm_dp_mst_handle_up_req.patch
queue-4.4/drm-mst-avoid-processing-partially-received-up-down-message-transactions.patch
queue-4.4/drm-mst-fix-error-handling-during-mst-sideband-message-reception.patch