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

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Date:   Thu, 17 Nov 2022 16:40:52 -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 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>


> ---
> 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
>