linux-kernel - Re: [PATCH] drm/i915/gvt/fb_decoder: Fix out-of-bounds read

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Date:   Tue, 12 Dec 2017 14:56:09 -0600
From:   "Gustavo A. R. Silva" <garsilva@...eddedor.com>
To:     Zhenyu Wang <zhenyuw@...ux.intel.com>
Cc:     Zhi Wang <zhi.a.wang@...el.com>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        David Airlie <airlied@...ux.ie>,
        intel-gfx@...ts.freedesktop.org,
        intel-gvt-dev@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH] drm/i915/gvt/fb_decoder: Fix out-of-bounds read

Hi Zhenyu,

Quoting Zhenyu Wang <zhenyuw@...ux.intel.com>:

> On 2017.12.09 00:37:59 -0600, Gustavo A. R. Silva wrote:
>> In case function skl_format_to_drm returns -EINVAL, fmt turns into a huge
>> number as fmt is of type u32, hence there is an out-of-bounds read when
>> using fmt as an index for array skl_pixel_formats at line 225:
>> plane->bpp = skl_pixel_formats[fmt].bpp;
>>
>> Fix this by comparing the value returned by function skl_format_to_drm
>> against the size of array skl_pixel_formats, so in case it is greater than
>> or equal to the number of items contained in skl_pixel_formats, print an
>> error message and return -EINVAL.
>>
>> Addresses-Coverity-ID: 1462495
>> Addresses-Coverity-ID: 1462502 ("Out-of-bounds read")
>> Fixes: 9f31d1063b43 ("drm/i915/gvt: Add framebuffer decoder support")
>> Signed-off-by: Gustavo A. R. Silva <garsilva@...eddedor.com>
>> ---
>>  drivers/gpu/drm/i915/gvt/fb_decoder.c | 6 ++++++
>>  1 file changed, 6 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/i915/gvt/fb_decoder.c  
>> b/drivers/gpu/drm/i915/gvt/fb_decoder.c
>> index 72f4217..aed578b 100644
>> --- a/drivers/gpu/drm/i915/gvt/fb_decoder.c
>> +++ b/drivers/gpu/drm/i915/gvt/fb_decoder.c
>> @@ -222,6 +222,12 @@ int intel_vgpu_decode_primary_plane(struct  
>> intel_vgpu *vgpu,
>>  			val & PLANE_CTL_ORDER_RGBX,
>>  			val & PLANE_CTL_ALPHA_MASK,
>>  			val & PLANE_CTL_YUV422_ORDER_MASK);
>> +
>> +		if (fmt >= ARRAY_SIZE(skl_pixel_formats)) {
>> +			gvt_vgpu_err("Out-of-bounds pixel format index\n");
>> +			return -EINVAL;
>> +		}
>> +
>>  		plane->bpp = skl_pixel_formats[fmt].bpp;
>>  		plane->drm_format = skl_pixel_formats[fmt].drm_format;
>>  	} else {
>> --
>
> Applied this, thanks!
>

Glad to help. :)

Thanks
--
Gustavo A. R. Silva