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In-Reply-To: <20161006180211.31747-1-colin.king@canonical.com>
References: <20161006180211.31747-1-colin.king@canonical.com>
From: Alex Deucher <alexdeucher@gmail.com>
Date: Thu, 6 Oct 2016 14:32:54 -0400
Message-ID: <CADnq5_NUGhR8SS=Am6O+wcSBpZAvxq9bXGe7dzsosnxE_QLjEQ@mail.gmail.com>
Subject: Re: [PATCH] drm/amd/amdgpu: default to zero number of states if not enabled
To: Colin King <colin.king@canonical.com>
Cc: Alex Deucher <alexander.deucher@amd.com>,
        =?UTF-8?Q?Christian_K=C3=B6nig?= <christian.koenig@amd.com>,
        David Airlie <airlied@linux.ie>, Eric Huang <JinHuiEric.Huang@amd.com>,
        Rex Zhu <Rex.Zhu@amd.com>, Jammy Zhou <Jammy.Zhou@amd.com>,
        Tom St Denis <tom.stdenis@amd.com>,
        Dan Carpenter <dan.carpenter@oracle.com>,
        Maling list - DRI developers 
        <dri-devel@lists.freedesktop.org>,
        LKML <linux-kernel@vger.kernel.org>
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On Thu, Oct 6, 2016 at 2:02 PM, Colin King <colin.king@canonical.com> wrote:
> From: Colin Ian King <colin.king@canonical.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?  The pp_num_states attribute only
gets added in the first place if pp_enabled is true.

Alex

>
> Signed-off-by: Colin Ian King <colin.king@canonical.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
>
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