[PATCH 4.19 049/346] drm: fix drm_dp_mst_port refcount leaks in drm_dp_mst_allocate_vcpi

Greg Kroah-Hartman
2020-12-28T13:22:21Z

From: Xin Xiong <xiongx18@fudan.edu.cn>

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: 1e797f556c61 ("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
[sudip: use old functions before rename]
Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@gmail.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
@@ -2706,11 +2706,11 @@ bool drm_dp_mst_allocate_vcpi(struct drm
{
int ret;

- port = drm_dp_get_validated_port_ref(mgr, port);
- if (!port)
+ if (slots < 0)
return false;

- if (slots < 0)
+ port = drm_dp_get_validated_port_ref(mgr, port);
+ if (!port)
return false;

if (port->vcpi.vcpi > 0) {
@@ -2725,6 +2725,7 @@ bool drm_dp_mst_allocate_vcpi(struct drm
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_put_port(port);
goto out;
}
DRM_DEBUG_KMS("initing vcpi for pbn=%d slots=%d\n",