Commit a34a0a63 authored Jul 19, 2020 by Xin Xiong Committed by Lyude Paul Aug 04, 2020

drm: fix drm_dp_mst_port refcount leaks in drm_dp_mst_allocate_vcpi



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

parent d88ca7e1

drivers/gpu/drm/drm_dp_mst_topology.c

+4 −3

Original line number	Diff line number	Diff line
		@@ -4308,11 +4308,11 @@ 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) {
		@@ -4328,6 +4328,7 @@ 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",

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