linux-kernel - Re: [Intel-gfx] 4.10-rc2 oops in DRM connector code

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <f56df02a-61ae-e20b-c99a-cfe8ccd45c64@intel.com>
Date:   Mon, 9 Jan 2017 08:50:22 -0800
From:   Dave Hansen <dave.hansen@...el.com>
To:     Daniel Vetter <daniel@...ll.ch>
Cc:     Daniel Vetter <daniel.vetter@...el.com>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        David Airlie <airlied@...ux.ie>,
        intel-gfx <intel-gfx@...ts.freedesktop.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [Intel-gfx] 4.10-rc2 oops in DRM connector code

On 01/09/2017 08:41 AM, Daniel Vetter wrote:
> On Mon, Jan 9, 2017 at 2:40 PM, Dave Hansen <dave.hansen@...el.com> wrote:
>> Well, now I found where the -2 comes from.
>> intel_dp_register_mst_connector() calls drm_connector_register(), which
>> fails to add the kobject (warning below).  But, it does zero error
>> checking on the drm_connector_register() call and leaves the
>> partially-constructed connector in place.
>>
>> The next time some poor, hapless code goes and tries to do anything with
>> that kdev, they oops.  I'm perplexed by this, though.  The
>> drm_dp_mst_topology_cbs->register_connector just returns void.  It seems
>> a bit goofy that it can't even _return_ failure.
>>
>> Is there some stable code to go back to here?  Or, is there something
>> about my configuration that's unique?  I really wonder why nobody else
>> is running into this.
>>
>> There's probably some other race going on here.  This warning doesn't
>> happen on every boot.
> This smells more like the root-cause: Something goes wrong on boot
> that prevents connectors from properly registering, then we fall over
> later on. And the register callback is intentionally void, assuming
> that any prep work has been done earlier and that therefore the
> register step can't fail. Can you pls check whether the oops later on
> only happens together with this warning at boot, or whether they're
> not correlated?

Looking through my logs, I can't find any instance of the oops without
the warning at boot.  So I do think the later oops is entirely caused by
the issue warned about in early boot.

My distro kernel (4.4.0-57-generic) is also unstable, but I haven't
managed to capture a good oops there.  It's hitting this, which I assume
is unrelated:

	WARNING: CPU: 0 PID: 41 at /build/linux-lts-xenial-FdAdUy/linux-
	lts-xenial-4.4.0/ubuntu/i915/intel_pm.c:3675
	skl_update_other_pipe_wm+0x191/0x1a0 [i915_bpo]()