[PATCH 3.19.y-ckt 122/155] drm: fix mutex leak in drm_dp_get_mst_branch_device

From: Kamal Mostafa
Date: Thu Nov 12 2015 - 18:20:01 EST

3.19.8-ckt10 -stable review patch. If anyone has any objections, please let me know.


From: Adam Richter <adamrichter4@xxxxxxxxx>

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@xxxxxxxxx>
Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
Signed-off-by: Dave Airlie <airlied@xxxxxxxxxx>
Signed-off-by: Kamal Mostafa <kamal@xxxxxxxxxxxxx>
drivers/gpu/drm/drm_dp_mst_topology.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index 1133179..df0fccb 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -1189,17 +1189,18 @@ static struct drm_dp_mst_branch *drm_dp_get_mst_branch_device(struct drm_dp_mst_

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;
return mstb;

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