[PATCH RESEND] drm/dp/mst: fix kernel oops when turning off secondary monitor

[PATCH RESEND] drm/dp/mst: fix kernel oops when turning off secondary monitor

[Jani Nikula]

From: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>

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 <airlied@redhat.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Nathan D Ciobanu <nathan.d.ciobanu@linux.intel.com>
Cc: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Cc: Sean Paul <seanpaul@chromium.org>
Cc: <stable@vger.kernel.org> # v3.18+
Tested-by: Nathan D Ciobanu <nathan.d.ciobanu@linux.intel.com>
Reviewed-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
---
 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

Re: [Intel-gfx] [PATCH RESEND] drm/dp/mst: fix kernel oops when turning off secondary monitor

[Daniel Vetter]

On Tue, Feb 14, 2017 at 02:49:21PM +0200, Jani Nikula wrote:
> From: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
> 
> 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 <airlied@redhat.com>
> Cc: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Nathan D Ciobanu <nathan.d.ciobanu@linux.intel.com>
> Cc: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
> Cc: Sean Paul <seanpaul@chromium.org>
> Cc: <stable@vger.kernel.org> # v3.18+
> Tested-by: Nathan D Ciobanu <nathan.d.ciobanu@linux.intel.com>
> Reviewed-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
> Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
> Signed-off-by: Jani Nikula <jani.nikula@intel.com>

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

Re: [Intel-gfx] [PATCH RESEND] drm/dp/mst: fix kernel oops when turning off secondary monitor

[Jani Nikula]

On Tue, 14 Feb 2017, Daniel Vetter <daniel@ffwll.ch> wrote:
> On Tue, Feb 14, 2017 at 02:49:21PM +0200, Jani Nikula wrote:
>> From: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
>> 
>> 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 <airlied@redhat.com>
>> Cc: Chris Wilson <chris@chris-wilson.co.uk>
>> Cc: Nathan D Ciobanu <nathan.d.ciobanu@linux.intel.com>
>> Cc: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
>> Cc: Sean Paul <seanpaul@chromium.org>
>> Cc: <stable@vger.kernel.org> # v3.18+
>> Tested-by: Nathan D Ciobanu <nathan.d.ciobanu@linux.intel.com>
>> Reviewed-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
>> Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
>> Signed-off-by: Jani Nikula <jani.nikula@intel.com>
>
> You haz drm-misc commit rights, pls use them :-)

Sure, I just wanted to have a fresh CI run on this.

> 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.

Will do.

BR,
Jani.

> -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

-- 
Jani Nikula, Intel Open Source Technology Center

Re: [Intel-gfx] [PATCH RESEND] drm/dp/mst: fix kernel oops when turning off secondary monitor

[Jani Nikula]

On Wed, 15 Feb 2017, Jani Nikula <jani.nikula@intel.com> wrote:
> On Tue, 14 Feb 2017, Daniel Vetter <daniel@ffwll.ch> wrote:
>> On Tue, Feb 14, 2017 at 02:49:21PM +0200, Jani Nikula wrote:
>>> From: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
>>> 
>>> 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 <airlied@redhat.com>
>>> Cc: Chris Wilson <chris@chris-wilson.co.uk>
>>> Cc: Nathan D Ciobanu <nathan.d.ciobanu@linux.intel.com>
>>> Cc: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
>>> Cc: Sean Paul <seanpaul@chromium.org>
>>> Cc: <stable@vger.kernel.org> # v3.18+
>>> Tested-by: Nathan D Ciobanu <nathan.d.ciobanu@linux.intel.com>
>>> Reviewed-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
>>> Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
>>> Signed-off-by: Jani Nikula <jani.nikula@intel.com>
>>
>> You haz drm-misc commit rights, pls use them :-)
>
> Sure, I just wanted to have a fresh CI run on this.
>
>> 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.
>
> Will do.

And pushed to drm-misc-fixes, thanks for the patch, review and testing.

BR,
Jani.



-- 
Jani Nikula, Intel Open Source Technology Center