From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Vetter Subject: Re: [Intel-gfx] [PATCH RESEND] drm/dp/mst: fix kernel oops when turning off secondary monitor Date: Tue, 14 Feb 2017 22:38:43 +0100 Message-ID: <20170214213843.GD11138@dvetter-linux.ger.corp.intel.com> References: <1487076561-2169-1-git-send-email-jani.nikula@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <1487076561-2169-1-git-send-email-jani.nikula@intel.com> Sender: stable-owner@vger.kernel.org To: Jani Nikula Cc: dri-devel@lists.freedesktop.org, intel-gfx@lists.freedesktop.org, stable@vger.kernel.org, Dhinakaran Pandiyan , Dave Airlie List-Id: intel-gfx@lists.freedesktop.org On Tue, Feb 14, 2017 at 02:49:21PM +0200, Jani Nikula wrote: > From: Pierre-Louis Bossart > > 100% reproducible issue found on SKL SkullCanyon NUC with two external > DP daisy-chained monitors in DP/MST mode. When turning off or changing > the input of the second monitor the machine stops with a kernel > oops. This issue happened with 4.8.8 as well as drm/drm-intel-nightly. > > This issue is traced to an inconsistent control flow in > drm_dp_update_payload_part1(): the 'port' pointer is set to NULL at the > same time as 'req_payload.num_slots' is set to zero, but the pointer is > dereferenced even when req_payload.num_slot is zero. > > The problematic dereference was introduced in commit dfda0df34 > ("drm/mst: rework payload table allocation to conform better") and may > impact all versions since v3.18 > > The fix suggested by Chris Wilson removes the kernel oops and was found to > work well after 10mn of monkey-testing with the second monitor power and > input buttons > > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=98990 > Fixes: dfda0df34264 ("drm/mst: rework payload table allocation to conform better.") > Cc: Dave Airlie > Cc: Chris Wilson > Cc: Nathan D Ciobanu > Cc: Dhinakaran Pandiyan > Cc: Sean Paul > Cc: # v3.18+ > Tested-by: Nathan D Ciobanu > Reviewed-by: Dhinakaran Pandiyan > Signed-off-by: Pierre-Louis Bossart > Signed-off-by: Jani Nikula You haz drm-misc commit rights, pls use them :-) Since it doesn't have deps, probably simplest to smash into drm-misc-fixes and then send a pull req to Dave right away. If you want, you can roll -fixes forward to -rc8 while at it. -Daniel > --- > drivers/gpu/drm/drm_dp_mst_topology.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c > index 122a1b04bebc..f2cc375907d0 100644 > --- a/drivers/gpu/drm/drm_dp_mst_topology.c > +++ b/drivers/gpu/drm/drm_dp_mst_topology.c > @@ -1817,7 +1817,7 @@ int drm_dp_update_payload_part1(struct drm_dp_mst_topology_mgr *mgr) > mgr->payloads[i].vcpi = req_payload.vcpi; > } else if (mgr->payloads[i].num_slots) { > mgr->payloads[i].num_slots = 0; > - drm_dp_destroy_payload_step1(mgr, port, port->vcpi.vcpi, &mgr->payloads[i]); > + drm_dp_destroy_payload_step1(mgr, port, mgr->payloads[i].vcpi, &mgr->payloads[i]); > req_payload.payload_state = mgr->payloads[i].payload_state; > mgr->payloads[i].start_slot = 0; > } > -- > 2.1.4 > > _______________________________________________ > Intel-gfx mailing list > Intel-gfx@lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/intel-gfx -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch