Patch "drm: fix mutex leak in drm_dp_get_mst_branch_device" has been added to the 4.2-stable tree

[<gregkh@linuxfoundation.org>]

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

    drm: fix mutex leak in drm_dp_get_mst_branch_device

to the 4.2-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-fix-mutex-leak-in-drm_dp_get_mst_branch_device.patch
and it can be found in the queue-4.2 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 30730c7f5943b3beace1e29f7f1476e05de3da14 Mon Sep 17 00:00:00 2001
From: Adam Richter <adamrichter4@gmail.com>
Date: Fri, 16 Oct 2015 03:33:02 -0700
Subject: drm: fix mutex leak in drm_dp_get_mst_branch_device

From: Adam Richter <adamrichter4@gmail.com>

commit 30730c7f5943b3beace1e29f7f1476e05de3da14 upstream.

In Linux 4.3-rc5, there is an error case in drm_dp_get_branch_device
that returns without releasing mgr->lock, resulting a spew of kernel
messages about a kernel work function possibly having leaked a mutex
and presumably more serious adverse consequences later.  This patch
changes the error to "goto out" to unlock the mutex before returning.

[airlied: grabbed from drm-next as it fixes something we've seen]

Signed-off-by: Adam J. Richter <adam_richter2004@yahoo.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/gpu/drm/drm_dp_mst_topology.c |    7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -1193,17 +1193,18 @@ static struct drm_dp_mst_branch *drm_dp_
 
 		list_for_each_entry(port, &mstb->ports, next) {
 			if (port->port_num == port_num) {
-				if (!port->mstb) {
+				mstb = port->mstb;
+				if (!mstb) {
 					DRM_ERROR("failed to lookup MSTB with lct %d, rad %02x\n", lct, rad[0]);
-					return NULL;
+					goto out;
 				}
 
-				mstb = port->mstb;
 				break;
 			}
 		}
 	}
 	kref_get(&mstb->kref);
+out:
 	mutex_unlock(&mgr->lock);
 	return mstb;
 }


Patches currently in stable-queue which might be from adamrichter4@gmail.com are

queue-4.2/drm-fix-mutex-leak-in-drm_dp_get_mst_branch_device.patch