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

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Message-ID: <57F6A01D.10907@canonical.com>
Date:   Thu, 6 Oct 2016 20:03:57 +0100
From:   Colin Ian King <colin.king@...onical.com>
To:     Alex Deucher <alexdeucher@...il.com>
Cc:     Alex Deucher <alexander.deucher@....com>,
        Christian König <christian.koenig@....com>,
        David Airlie <airlied@...ux.ie>,
        Eric Huang <JinHuiEric.Huang@....com>,
        Rex Zhu <Rex.Zhu@....com>, Jammy Zhou <Jammy.Zhou@....com>,
        Tom St Denis <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 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?

> 
> 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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