On Mon, 19 Sep 2022, Zheng Wang <1002992920@xxxxxx> wrote:
> From afe79848cb74cc8e45ab426d13fa2394c87e0422 Mon Sep 17 00:00:00 2001
> From: xmzyshypnc <1002992920@xxxxxx>
> 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: xmzyshypnc <1002992920@xxxxxx>
Please use git send-email. The patch is whitespace broken and line
wrapped, making it unusable.
BR,
Jani.
> ---
> 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,
> ops->get_pfn(e));
> return -ENXIO;
> }
> - return ppgtt_invalidate_spt(s);
> + return ppgtt_invalidate_spt(s, 0);
> }
>
> static inline void ppgtt_invalidate_pte(struct intel_vgpu_ppgtt_spt *spt,
> @@ -1016,7 +1016,7 @@ static inline void ppgtt_invalidate_pte(struct
> intel_vgpu_ppgtt_spt *spt,
> intel_gvt_dma_unmap_guest_page(vgpu, pfn << PAGE_SHIFT);
> }
>
> -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)
> {
> struct intel_vgpu *vgpu = spt->vgpu;
> struct intel_gvt_gtt_entry e;
> @@ -1059,9 +1059,11 @@ static int ppgtt_invalidate_spt(struct
> intel_vgpu_ppgtt_spt *spt)
> }
> }
>
> - trace_spt_change(spt->vgpu->id, "release", spt,
> + if (!is_error) {
> + trace_spt_change(spt->vgpu->id, "release", spt,
> spt->guest_page.gfn, spt->shadow_page.type);
> - ppgtt_free_spt(spt);
> + ppgtt_free_spt(spt);
> + }
> return 0;
> fail:
> gvt_vgpu_err("fail: shadow page %p shadow entry 0x%llx type %d\n",
> @@ -1215,7 +1217,7 @@ static int split_2MB_gtt_entry(struct intel_vgpu
> *vgpu,
> ret = intel_gvt_dma_map_guest_page(vgpu, start_gfn + sub_index,
> PAGE_SIZE, &dma_addr);
> if (ret) {
> - ppgtt_invalidate_spt(spt);
> + ppgtt_invalidate_spt(spt, 1);
> return ret;
> }
> sub_se.val64 = se->val64;
> @@ -1393,7 +1395,7 @@ static int ppgtt_handle_guest_entry_removal(struct
> intel_vgpu_ppgtt_spt *spt,
> ret = -ENXIO;
> goto fail;
> }
> - ret = ppgtt_invalidate_spt(s);
> + ret = ppgtt_invalidate_spt(s, 0);
> if (ret)
> goto fail;
> } else {
--
Jani Nikula, Intel Open Source Graphics Center
