linux-kernel - Re: [PATCH] drm: make drm_dp_add_payload_part2 gracefully handle NULL state pointer

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: <b99732f7c0dd968c0702ae7629695e8fb9cb573f.camel@kernel.org>
Date:   Mon, 17 Apr 2023 06:06:37 -0400
From:   Jeff Layton <jlayton@...nel.org>
To:     Jani Nikula <jani.nikula@...ux.intel.com>,
        Lyude Paul <lyude@...hat.com>,
        "Lin, Wayne" <Wayne.Lin@....com>,
        Alex Deucher <alexdeucher@...il.com>
Cc:     David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>,
        "Deucher, Alexander" <Alexander.Deucher@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>
Subject: Re: [PATCH] drm: make drm_dp_add_payload_part2 gracefully handle
 NULL state pointer

On Mon, 2023-04-17 at 11:44 +0300, Jani Nikula wrote:
> On Fri, 14 Apr 2023, Lyude Paul <lyude@...hat.com> wrote:
> > On Fri, 2023-04-14 at 13:35 +0300, Jani Nikula wrote:
> > > On Fri, 14 Apr 2023, Jeff Layton <jlayton@...nel.org> wrote:
> > > > On Fri, 2023-04-14 at 04:40 +0000, Lin, Wayne wrote:
> > > > > [Public]
> > > > > 
> > > > > Hi Jeff,
> > > > > 
> > > > > Thanks. I might need more information to understand why we can't retrieve
> > > > > the drm atomic state. Also , "Failed to create MST payload for port" indicates
> > > > > error while configuring DPCD payload ID table. Could you help to provide log
> > > > > with KMS + ATOMIC + DP debug on please? Thanks in advance!
> > > > > 
> > > > > Regards,
> > > > > Wayne
> > > > > 
> > > > 
> > > > Possibly. I'm not that familiar with display driver debugging. Can you
> > > > send me some directions on how to crank up that sort of debug logging?
> > > > 
> > > > Note that this problem is _very_ intermittent too: I went about 2 weeks
> > > > between crashes, and then I got 3 in one day. I'd rather not run with a
> > > > lot of debug logging for a long time if that's what this is going to
> > > > require, as this is my main workstation.
> > > > 
> > > > The last time I got this log message, my proposed patch did prevent the
> > > > box from oopsing, so I'd really like to see it go in unless it's just
> > > > categorically wrong for the caller to pass down a NULL state pointer to
> > > > drm_dp_add_payload_part2.
> > > 
> > > Cc: Lyude.
> > > 
> > > Looks like the state parameter was added in commit 4d07b0bc4034
> > > ("drm/display/dp_mst: Move all payload info into the atomic state") and
> > > its only use is to get at state->dev for debug logging.
> > > 
> > > What's the plan for the parameter? Surely something more than that! :)
> > 
> > I don't think there was any plan for that, or at least I certainly don't even
> > remember adding that D:. It must totally have been by mistake and snuck by
> > review, if that's the only thing that we're using it for I'd say it's
> > definitely fine to just drop it entirely
> 
> I guess we could use two patches then, first replace state->dev with
> mgr->dev as something that can be backported as needed, and second drop
> the state parameter altogether.
> 
> Jeff, up for it? At least the first one?
> 
> 
> BR,
> Jani.
> 

Sure. I'm happy to test patches if you send them along.

Thanks,
-- 
Jeff Layton <jlayton@...nel.org>