From e51d7655d3dcac3ea2185fec178872b11b9f03be Mon Sep 17 00:00:00 2001 From: "cpaul@redhat.com" Date: Mon, 4 Apr 2016 19:58:47 -0400 Subject: [PATCH] drm/dp/mst: Validate port in drm_dp_payload_send_msg() MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit commit deba0a2af9592b2022a0bce7b085a318b53ce1db upstream. With the joys of things running concurrently, there's always a chance that the port we get passed in drm_dp_payload_send_msg() isn't actually valid anymore. Because of this, we need to make sure we validate the reference to the port before we use it otherwise we risk running into various race conditions. For instance, on the Dell MST monitor I have here for testing, hotplugging it enough times causes us to kernel panic: [drm:intel_mst_enable_dp] 1 [drm:drm_dp_update_payload_part2] payload 0 1 [drm:intel_get_hpd_pins] hotplug event received, stat 0x00200000, dig 0x10101011, pins 0x00000020 [drm:intel_hpd_irq_handler] digital hpd port B - short [drm:intel_dp_hpd_pulse] got hpd irq on port B - short [drm:intel_dp_check_mst_status] got esi 00 10 00 [drm:drm_dp_update_payload_part2] payload 1 1 general protection fault: 0000 [#1] SMP … Call Trace: [] drm_dp_update_payload_part2+0xc2/0x130 [drm_kms_helper] [] intel_mst_enable_dp+0xf8/0x180 [i915] [] haswell_crtc_enable+0x3ed/0x8c0 [i915] [] intel_atomic_commit+0x5ad/0x1590 [i915] [] ? drm_atomic_set_crtc_for_connector+0x57/0xe0 [drm] [] drm_atomic_commit+0x37/0x60 [drm] [] drm_atomic_helper_set_config+0x7a/0xb0 [drm_kms_helper] [] drm_mode_set_config_internal+0x62/0x100 [drm] [] drm_mode_setcrtc+0x3cd/0x4e0 [drm] [] drm_ioctl+0x143/0x510 [drm] [] ? drm_mode_setplane+0x1b0/0x1b0 [drm] [] ? hrtimer_start_range_ns+0x1b7/0x3a0 [] do_vfs_ioctl+0x92/0x570 [] ? __sys_recvmsg+0x42/0x80 [] SyS_ioctl+0x79/0x90 [] entry_SYSCALL_64_fastpath+0x1a/0xa4 RIP [] drm_dp_payload_send_msg+0x146/0x1f0 [drm_kms_helper] Which occurs because of the hotplug event shown in the log, which ends up causing DRM's dp helpers to drop the port we're updating the payload on and panic. Signed-off-by: Lyude Reviewed-by: David Airlie Signed-off-by: Dave Airlie Signed-off-by: Greg Kroah-Hartman --- drivers/gpu/drm/drm_dp_mst_topology.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c index 39d7e2e15c11..a4a3de372b69 100644 --- a/drivers/gpu/drm/drm_dp_mst_topology.c +++ b/drivers/gpu/drm/drm_dp_mst_topology.c @@ -1665,13 +1665,19 @@ static int drm_dp_payload_send_msg(struct drm_dp_mst_topology_mgr *mgr, struct drm_dp_mst_branch *mstb; int len, ret, port_num; + port = drm_dp_get_validated_port_ref(mgr, port); + if (!port) + return -EINVAL; + port_num = port->port_num; mstb = drm_dp_get_validated_mstb_ref(mgr, port->parent); if (!mstb) { mstb = drm_dp_get_last_connected_port_and_mstb(mgr, port->parent, &port_num); - if (!mstb) + if (!mstb) { + drm_dp_put_port(port); return -EINVAL; + } } txmsg = kzalloc(sizeof(*txmsg), GFP_KERNEL); @@ -1697,6 +1703,7 @@ static int drm_dp_payload_send_msg(struct drm_dp_mst_topology_mgr *mgr, kfree(txmsg); fail_put: drm_dp_put_mst_branch_device(mstb); + drm_dp_put_port(port); return ret; } -- 2.34.1