From: Dave Airlie airlied@redhat.com
We should validate the passed in mstb under the lock this should stop us getting an invalid mstb here.
(first attempt with cancelling work has lockdep issues). Bugzilla: https://bugs.archlinux.org/task/45369
v2: update bugzilla, add some notes on why passing mst_primary is okay.
Signed-off-by: Dave Airlie airlied@redhat.com --- drivers/gpu/drm/drm_dp_mst_topology.c | 17 +++++++++++++++-- 1 file changed, 15 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c index fb65f5d..3c7e5cd 100644 --- a/drivers/gpu/drm/drm_dp_mst_topology.c +++ b/drivers/gpu/drm/drm_dp_mst_topology.c @@ -1198,9 +1198,14 @@ static struct drm_dp_mst_branch *drm_dp_get_mst_branch_device(struct drm_dp_mst_ }
static void drm_dp_check_and_send_link_address(struct drm_dp_mst_topology_mgr *mgr, - struct drm_dp_mst_branch *mstb) + struct drm_dp_mst_branch *mstb_in) { struct drm_dp_mst_port *port; + struct drm_dp_mst_branch *mstb; + + mstb = drm_dp_get_validated_mstb_ref(mgr, mstb_in); + if (!mstb) + return;
if (!mstb->link_address_sent) { drm_dp_send_link_address(mgr, mstb); @@ -1219,12 +1224,20 @@ static void drm_dp_check_and_send_link_address(struct drm_dp_mst_topology_mgr *m if (port->mstb) drm_dp_check_and_send_link_address(mgr, port->mstb); } + drm_dp_put_mst_branch_device(mstb); }
static void drm_dp_mst_link_probe_work(struct work_struct *work) { struct drm_dp_mst_topology_mgr *mgr = container_of(work, struct drm_dp_mst_topology_mgr, work); - + /* + * Note this passes mgr->mst_primary without validation + * it could be a) valid, b) NULL, c) some value between + * since we haven't taken the lock, + * however the validation sequence in check and send + * will take the lock, and if the value isn't valid + * it will fail appropriately. + */ drm_dp_check_and_send_link_address(mgr, mgr->mst_primary);
}