Re: [PATCH] drm/i915/gvt: fix double-free bug in split_2MB_gtt_entry.

From: Zheng Hacker <hackerzheng666@gmail.com>
To: Greg KH <gregkh@linuxfoundation.org>
Cc: "alex000young@gmail.com" <alex000young@gmail.com>,
	"security@kernel.org" <security@kernel.org>,
	"tvrtko.ursulin@linux.intel.com" <tvrtko.ursulin@linux.intel.com>,
	"airlied@linux.ie" <airlied@linux.ie>,
	"intel-gfx@lists.freedesktop.org"
	<intel-gfx@lists.freedesktop.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"dri-devel@lists.freedesktop.org"
	<dri-devel@lists.freedesktop.org>, xmzyshypnc <1002992920@qq.com>,
	"rodrigo.vivi@intel.com" <rodrigo.vivi@intel.com>,
	"intel-gvt-dev@lists.freedesktop.org"
	<intel-gvt-dev@lists.freedesktop.org>,
	"zhi.a.wang@intel.com" <zhi.a.wang@intel.com>
Subject: Re: [PATCH] drm/i915/gvt: fix double-free bug in split_2MB_gtt_entry.
Date: Sat, 17 Sep 2022 17:10:48 +0800	[thread overview]
Message-ID: <CAJedcCyx+qYpPd-_vqg0vQO9nQVrwBXARv3Lzi+FJ4HrBN0AGQ@mail.gmail.com> (raw)
In-Reply-To: <YyWOh+jGvmSdrHqz@kroah.com>

[-- Attachment #1: Type: text/plain, Size: 1992 bytes --]

Hi Greg,

Sorry for that. I’ll write another one.

Regards,
Zheng Wang

在 2022年9月17日星期六，Greg KH <gregkh@linuxfoundation.org> 写道：

> On Fri, Sep 16, 2022 at 11:54:42PM +0800, Zheng Hacker wrote:
> > >From afe79848cb74cc8e45ab426d13fa2394c87e0422 Mon Sep 17 00:00:00 2001
> > From: xmzyshypnc <1002992920@qq.com>
> > Date: Fri, 16 Sep 2022 23:48:23 +0800
> > Subject: [PATCH] drm/i915/gvt: fix double-free bug in split_2MB_gtt_entry
> >
> > There is a double-free security bug in split_2MB_gtt_entry.
> >
> > Here is a calling chain :
> > ppgtt_populate_spt->ppgtt_populate_shadow_entry->split_2MB_gtt_entry.
> >
> > If intel_gvt_dma_map_guest_page failed, it will call
> > ppgtt_invalidate_spt, which will finally call ppgtt_free_spt and
> > kfree(spt). But the caller does not notice that, and it will call
> > ppgtt_free_spt again in error path.
> >
> > Fix this by only freeing spt in ppgtt_invalidate_spt in good case.
> >
> > Signed-off-by: Zheng Wang <hackerzheng666@gmail.com>
> > ---
> >  drivers/gpu/drm/i915/gvt/gtt.c | 16 +++++++++-------
> >  1 file changed, 9 insertions(+), 7 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/gvt/gtt.c b/drivers/gpu/drm/i915/gvt/
> gtt.c
> > index ce0eb03709c3..550519f0acca 100644
> > --- a/drivers/gpu/drm/i915/gvt/gtt.c
> > +++ b/drivers/gpu/drm/i915/gvt/gtt.c
> > @@ -959,7 +959,7 @@ static inline int ppgtt_put_spt(struct
> > intel_vgpu_ppgtt_spt *spt)
> >     return atomic_dec_return(&spt->refcount);
> >  }
> >
> > -static int ppgtt_invalidate_spt(struct intel_vgpu_ppgtt_spt *spt);
> > +static int ppgtt_invalidate_spt(struct intel_vgpu_ppgtt_spt *spt, int
> > is_error);
> >
> >  static int ppgtt_invalidate_spt_by_shadow_entry(struct intel_vgpu
> *vgpu,
> >         struct intel_gvt_gtt_entry *e)
> > @@ -995,7 +995,7 @@ static int
> > ppgtt_invalidate_spt_by_shadow_entry(struct intel_vgpu *vgpu,
>
> Still line-wrapped and whitespace broken :(
>
>

[-- Attachment #2: Type: text/html, Size: 2598 bytes --]