linux-kernel - Re: [PATCH v5 1/2] drm/amd: validate user pitch alignment

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Date:   Mon, 7 Jan 2019 10:54:03 +0100
From:   Michel Dänzer <michel@...nzer.net>
To:     Yu Zhao <yuzhao@...gle.com>
Cc:     David Zhou <David1.Zhou@....com>,
        Daniel Stone <daniels@...labora.com>,
        David Airlie <airlied@...ux.ie>, linux-kernel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org,
        Junwei Zhang <Jerry.Zhang@....com>,
        amd-gfx@...ts.freedesktop.org, Daniel Vetter <daniel@...ll.ch>,
        Alex Deucher <alexander.deucher@....com>,
        stable@...r.kernel.org, Harry Wentland <harry.wentland@....com>,
        Christian König <christian.koenig@....com>,
        Samuel Li <Samuel.Li@....com>
Subject: Re: [PATCH v5 1/2] drm/amd: validate user pitch alignment

On 2019-01-07 5:00 a.m., Yu Zhao wrote:
> On Thu, Jan 03, 2019 at 05:33:19PM +0100, Michel Dänzer wrote:
>> On 2018-12-30 2:00 a.m., Yu Zhao wrote:
>>> Userspace may request pitch alignment that is not supported by GPU.
>>> Some requests 32, but GPU ignores it and uses default 64 when cpp is
>>> 4. If GEM object is allocated based on the smaller alignment, GPU
>>> DMA will go out of bound.
>>>
>>> Cc: stable@...r.kernel.org # v4.2+
>>> Signed-off-by: Yu Zhao <yuzhao@...gle.com>
>>> ---
>>>  drivers/gpu/drm/amd/amdgpu/amdgpu_display.c | 16 ++++++++++++++++
>>>  1 file changed, 16 insertions(+)
>>>
>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_display.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_display.c
>>> index 15ce7e681d67..16af80ccd0a0 100644
>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_display.c
>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_display.c
>>> @@ -527,6 +527,22 @@ amdgpu_display_user_framebuffer_create(struct drm_device *dev,
>>>  	struct drm_gem_object *obj;
>>>  	struct amdgpu_framebuffer *amdgpu_fb;
>>>  	int ret;
>>> +	struct amdgpu_device *adev = dev->dev_private;
>>> +	int cpp = drm_format_plane_cpp(mode_cmd->pixel_format, 0);
>>> +	int pitch = mode_cmd->pitches[0] / cpp;
>>> +
>>> +	if (pitch < mode_cmd->width) {
>>> +		DRM_DEBUG_KMS("Expecting pitch(%d)/cpp(%d) >= width(%d)\n",
>>> +			      mode_cmd->pitches[0], cpp, mode_cmd->width);
>>> +		return ERR_PTR(-EINVAL);
>>> +	}
>>
>> This should possibly be tested in drm_internal_framebuffer_create instead.
> 
> It seems to me drm_format_info_min_pitch() in framebuffer_check()
> already does it. We could just remove the check here?

Yeah, looks like that should be fine.


-- 
Earthling Michel Dänzer               |               http://www.amd.com
Libre software enthusiast             |             Mesa and X developer