Commit 915ad46b authored Jul 19, 2020 by Xin Xiong Committed by Greg Kroah-Hartman Aug 21, 2020

drm: fix drm_dp_mst_port refcount leaks in drm_dp_mst_allocate_vcpi



commit a34a0a632dd991a371fec56431d73279f9c54029 upstream.

drm_dp_mst_allocate_vcpi() invokes
drm_dp_mst_topology_get_port_validated(), which increases the refcount
of the "port".

These reference counting issues take place in two exception handling
paths separately. Either when “slots” is less than 0 or when
drm_dp_init_vcpi() returns a negative value, the function forgets to
reduce the refcnt increased drm_dp_mst_topology_get_port_validated(),
which results in a refcount leak.

Fix these issues by pulling up the error handling when "slots" is less
than 0, and calling drm_dp_mst_topology_put_port() before termination
when drm_dp_init_vcpi() returns a negative value.

Fixes: 1e797f55 ("drm/dp: Split drm_dp_mst_allocate_vcpi")
Cc: <stable@vger.kernel.org> # v4.12+
Signed-off-by: Xiyu Yang <xiyuyang19@fudan.edu.cn>
Signed-off-by: Xin Tan <tanxin.ctf@gmail.com>
Signed-off-by: Xin Xiong <xiongx18@fudan.edu.cn>
Reviewed-by: Lyude Paul <lyude@redhat.com>
Signed-off-by: Lyude Paul <lyude@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200719154545.GA41231@xin-virtual-machine


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent f9f53b7c

drivers/gpu/drm/drm_dp_mst_topology.c

+4 −3

Original line number	Diff line number	Diff line
		@@ -3369,11 +3369,11 @@ bool drm_dp_mst_allocate_vcpi(struct drm_dp_mst_topology_mgr *mgr,
		{
		int ret;

		port = drm_dp_mst_topology_get_port_validated(mgr, port);
		if (!port)
		if (slots < 0)
		return false;

		if (slots < 0)
		port = drm_dp_mst_topology_get_port_validated(mgr, port);
		if (!port)
		return false;

		if (port->vcpi.vcpi > 0) {
		@@ -3389,6 +3389,7 @@ bool drm_dp_mst_allocate_vcpi(struct drm_dp_mst_topology_mgr *mgr,
		if (ret) {
		DRM_DEBUG_KMS("failed to init vcpi slots=%d max=63 ret=%d\n",
		DIV_ROUND_UP(pbn, mgr->pbn_div), ret);
		drm_dp_mst_topology_put_port(port);
		goto out;
		}
		DRM_DEBUG_KMS("initing vcpi for pbn=%d slots=%d\n",