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.
Signed-off-by: Adam J. Richter adam_richter2004@yahoo.com ---
bugzilla.freedesktop.org ticket: https://bugs.freedesktop.org/show_bug.cgi?id=92480
This patch is against the latest git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git . I apologize in advance in I should be submitting patches against some other reference. Please feel free to let me know if I should use some other reference for submitting future patches.
My request to subscribe to dri-devel@lists.freedesktop.org is pending, so I apologize if it takes a while for this message to be posted on the mailing list.
diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c index bf27a07..018ad7f 100644 --- a/drivers/gpu/drm/drm_dp_mst_topology.c +++ b/drivers/gpu/drm/drm_dp_mst_topology.c @@ -1194,17 +1194,18 @@ 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; break; } } } kref_get(&mstb->kref); + out: mutex_unlock(&mgr->lock); return mstb; }