[PATCH 4.1 14/86] drm: fix mutex leak in drm_dp_get_mst_branch_device

Greg Kroah-Hartman
2015-11-06T20:26:40Z

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
@@ -1179,17 +1179,18 @@ 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;
}