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

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Message-ID: <8947162f-762e-5ee1-5be7-73ba641149d0@amd.com>
Date:   Fri, 18 Nov 2022 16:05:10 -0500
From:   Harry Wentland <harry.wentland@....com>
To:     Alex Deucher <alexdeucher@...il.com>, Lyude Paul <lyude@...hat.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 11/18/22 15:25, Alex Deucher wrote:
> 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!
> 

Good catch. I seem to recall some DCE generations had an extra audio
device and if DCE12 defines 7 audio instances then this is the correct
fix.

Reviewed-by: Harry Wentland <harry.wentland@....com>

Harry

> 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
>>>