linux-kernel - Re: [PATCH] drm/amd/dc/dce120: Fix audio register mapping, stop triggering KASAN

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Date:   Fri, 18 Nov 2022 15:25:06 -0500
From:   Alex Deucher <alexdeucher@...il.com>
To:     Lyude Paul <lyude@...hat.com>,
        "Wentland, Harry" <Harry.Wentland@....com>
Cc:     amd-gfx@...ts.freedesktop.org, Alan Liu <HaoPing.Liu@....com>,
        Leo Li <sunpeng.li@....com>, David Airlie <airlied@...il.com>,
        "Pan, Xinhui" <Xinhui.Pan@....com>,
        Rodrigo Siqueira <Rodrigo.Siqueira@....com>,
        open list <linux-kernel@...r.kernel.org>,
        stable@...r.kernel.org,
        Aurabindo Pillai <aurabindo.pillai@....com>,
        "open list:DRM DRIVERS" <dri-devel@...ts.freedesktop.org>,
        Daniel Vetter <daniel@...ll.ch>,
        Alex Deucher <alexander.deucher@....com>,
        Christian König <christian.koenig@....com>
Subject: Re: [PATCH] drm/amd/dc/dce120: Fix audio register mapping, stop
 triggering KASAN

On Thu, Nov 17, 2022 at 4:40 PM Alex Deucher <alexdeucher@...il.com> wrote:
>
> On Mon, Nov 14, 2022 at 5:21 PM Lyude Paul <lyude@...hat.com> wrote:
> >
> > There's been a very long running bug that seems to have been neglected for
> > a while, where amdgpu consistently triggers a KASAN error at start:
> >
> >   BUG: KASAN: global-out-of-bounds in read_indirect_azalia_reg+0x1d4/0x2a0 [amdgpu]
> >   Read of size 4 at addr ffffffffc2274b28 by task modprobe/1889
> >
> > After digging through amd's rather creative method for accessing registers,
> > I eventually discovered the problem likely has to do with the fact that on
> > my dce120 GPU there are supposedly 7 sets of audio registers. But we only
> > define a register mapping for 6 sets.
> >
> > So, fix this and fix the KASAN warning finally.
> >
> > Signed-off-by: Lyude Paul <lyude@...hat.com>
> > Cc: stable@...r.kernel.org
>
> This is the correct fix for asics having 7 audio instances.  It looks
> correct to me, assuming DCE12 actually has 7 audio instances.
> @Wentland, Harry Do you know off hand?  If you can confirm that, the
> patch is:
> Reviewed-by: Alex Deucher <alexander.deucher@....com>

The driver currently defines 7 audio instances, whether or not it
actually has 7 remains to be seen but the code as is is broken, so
I'll apply this.  If it turns out there are only 6 instances we can
fix the count later.  Applied.  Thanks!

Alex

>
>
> > ---
> > Sending this one separately from the rest of my fixes since:
> >
> > * It's definitely completely unrelated to the Gitlab 2171 issue
> > * I'm not sure if this is the correct fix since it's in DC
> >
> >  drivers/gpu/drm/amd/display/dc/dce120/dce120_resource.c | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/amd/display/dc/dce120/dce120_resource.c b/drivers/gpu/drm/amd/display/dc/dce120/dce120_resource.c
> > index 1b70b78e2fa15..af631085e88c5 100644
> > --- a/drivers/gpu/drm/amd/display/dc/dce120/dce120_resource.c
> > +++ b/drivers/gpu/drm/amd/display/dc/dce120/dce120_resource.c
> > @@ -359,7 +359,8 @@ static const struct dce_audio_registers audio_regs[] = {
> >         audio_regs(2),
> >         audio_regs(3),
> >         audio_regs(4),
> > -       audio_regs(5)
> > +       audio_regs(5),
> > +       audio_regs(6),
> >  };
> >
> >  #define DCE120_AUD_COMMON_MASK_SH_LIST(mask_sh)\
> > --
> > 2.37.3
> >