linux-kernel - Re: [PATCH] drm/amd/amdgpu: default to zero number of states if not enabled

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Message-ID: <57F6A096.9040701@canonical.com>
Date:   Thu, 6 Oct 2016 20:05:58 +0100
From:   Colin Ian King <colin.king@...onical.com>
To:     "Deucher, Alexander" <Alexander.Deucher@....com>,
        Alex Deucher <alexdeucher@...il.com>
Cc:     "Koenig, Christian" <Christian.Koenig@....com>,
        David Airlie <airlied@...ux.ie>,
        "Huang, JinHuiEric" <JinHuiEric.Huang@....com>,
        "Zhu, Rex" <Rex.Zhu@....com>, "Zhou, Jammy" <Jammy.Zhou@....com>,
        "StDenis, Tom" <Tom.StDenis@....com>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Maling list - DRI developers 
        <dri-devel@...ts.freedesktop.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drm/amd/amdgpu: default to zero number of states if not
 enabled

On 06/10/16 20:04, Deucher, Alexander wrote:
>> -----Original Message-----
>> From: Colin Ian King [mailto:colin.king@...onical.com]
>> Sent: Thursday, October 06, 2016 3:04 PM
>> To: Alex Deucher
>> Cc: Deucher, Alexander; Koenig, Christian; David Airlie; Huang, JinHuiEric;
>> Zhu, Rex; Zhou, Jammy; StDenis, Tom; Dan Carpenter; Maling list - DRI
>> developers; LKML
>> Subject: Re: [PATCH] drm/amd/amdgpu: default to zero number of states if
>> not enabled
>>
>> On 06/10/16 19:32, Alex Deucher wrote:
>>> On Thu, Oct 6, 2016 at 2:02 PM, Colin King <colin.king@...onical.com>
>> wrote:
>>>> From: Colin Ian King <colin.king@...onical.com>
>>>>
>>>> Currently, if adev->pp_enabled is false then the pp_stats_info data
>>>> is not read and hence a garbage number of states from the stack
>>>> is used to dump out the number of states. Given data.nums could be
>>>> any random value, this could easily lead to read outside the
>>>> data.states array.  Fix this by setting data.nums to zero if
>>>> adev->pp_enabled is false.
>>>
>>> Are you actually seeing a problem?
>>
>> Nope.
>>
>>> The pp_num_states attribute only
>>> gets added in the first place if pp_enabled is true.
>>
>> Does that mean that the check on adev->pp_enabled is redundant then?
> 
> Yes, I think so.

OK, in which case it's probably extraneous code that could be removed.
> 
> Alex
> 
>>
>>>
>>> Alex
>>
>>>
>>>>
>>>> Signed-off-by: Colin Ian King <colin.king@...onical.com>
>>>> ---
>>>>  drivers/gpu/drm/amd/amdgpu/amdgpu_pm.c | 2 ++
>>>>  1 file changed, 2 insertions(+)
>>>>
>>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_pm.c
>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_pm.c
>>>> index accc908..808d788 100644
>>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_pm.c
>>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_pm.c
>>>> @@ -195,6 +195,8 @@ static ssize_t amdgpu_get_pp_num_states(struct
>> device *dev,
>>>>
>>>>         if (adev->pp_enabled)
>>>>                 amdgpu_dpm_get_pp_num_states(adev, &data);
>>>> +       else
>>>> +               data.nums = 0;
>>>>
>>>>         buf_len = snprintf(buf, PAGE_SIZE, "states: %d\n", data.nums);
>>>>         for (i = 0; i < data.nums; i++)
>>>> --
>>>> 2.9.3
>>>>
>>>> _______________________________________________
>>>> dri-devel mailing list
>>>> dri-devel@...ts.freedesktop.org
>>>> https://lists.freedesktop.org/mailman/listinfo/dri-devel
>

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