linux-kernel - Re: [PATCH] drm/i915/kvmgt: avoid dereferencing a potentially null info pointer

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Date:   Thu, 23 Mar 2017 12:39:00 +0000
From:   Chris Wilson <chris@...is-wilson.co.uk>
To:     Colin King <colin.king@...onical.com>
Cc:     Zhenyu Wang <zhenyuw@...ux.intel.com>,
        Zhi Wang <zhi.a.wang@...el.com>,
        Daniel Vetter <daniel.vetter@...el.com>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        David Airlie <airlied@...ux.ie>,
        intel-gvt-dev@...ts.freedesktop.org,
        intel-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/i915/kvmgt: avoid dereferencing a potentially null
 info pointer

On Thu, Mar 23, 2017 at 12:22:30PM +0000, Colin King wrote:
> From: Colin Ian King <colin.king@...onical.com>
> 
> info is being checked to see if it is a null pointer, however, vpgu is
> dereferencing info before this check, leading to a potential null
> pointer dereference.  If info is null, then the error message being
> printed by macro gvt_vgpu_err and this requires vpgu to exist. We can
> use a null vpgu as the macro has a sanity check to see if vpgu is null,
> so this is OK.

It is never NULL, it gets checked by its only caller.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre