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-vir... 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 @@ -3369,11 +3369,11 @@ bool drm_dp_mst_allocate_vcpi(struct drm { 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 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",