[PATCH v3] drm/i915/gvt: fix double free bug in split_2MB_gtt_entry
Dave Airlie
airlied at gmail.com
Thu Oct 27 00:01:29 UTC 2022
On Fri, 7 Oct 2022 at 11:38, Zheng Wang <zyytlz.wz at 163.com> wrote:
>
> If intel_gvt_dma_map_guest_page failed, it will call
> ppgtt_invalidate_spt, which will finally free the spt.
> But the caller does not notice that, it will free spt again in error path.
>
> Fix this by spliting invalidate and free in ppgtt_invalidate_spt.
> Only free spt when in good case.
>
> Reported-by: Zheng Wang <hackerzheng666 at gmail.com>
> Signed-off-by: Zheng Wang <zyytlz.wz at 163.com>
Has this landed in a tree yet, since it's a possible CVE, might be
good to merge it somewhere.
Dave.
> ---
> v3:
> - correct spelling mistake and remove unused variable suggested by Greg
>
> v2: https://lore.kernel.org/all/20221006165845.1735393-1-zyytlz.wz@163.com/
>
> v1: https://lore.kernel.org/all/20220928033340.1063949-1-zyytlz.wz@163.com/
> ---
> drivers/gpu/drm/i915/gvt/gtt.c | 32 +++++++++++++++++++++-----------
> 1 file changed, 21 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gvt/gtt.c b/drivers/gpu/drm/i915/gvt/gtt.c
> index ce0eb03709c3..865d33762e45 100644
> --- a/drivers/gpu/drm/i915/gvt/gtt.c
> +++ b/drivers/gpu/drm/i915/gvt/gtt.c
> @@ -959,6 +959,7 @@ static inline int ppgtt_put_spt(struct intel_vgpu_ppgtt_spt *spt)
> return atomic_dec_return(&spt->refcount);
> }
>
> +static int ppgtt_invalidate_and_free_spt(struct intel_vgpu_ppgtt_spt *spt);
> static int ppgtt_invalidate_spt(struct intel_vgpu_ppgtt_spt *spt);
>
> static int ppgtt_invalidate_spt_by_shadow_entry(struct intel_vgpu *vgpu,
> @@ -995,7 +996,7 @@ 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_and_free_spt(s);
> }
>
> static inline void ppgtt_invalidate_pte(struct intel_vgpu_ppgtt_spt *spt,
> @@ -1016,18 +1017,30 @@ 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_and_free_spt(struct intel_vgpu_ppgtt_spt *spt)
> {
> - struct intel_vgpu *vgpu = spt->vgpu;
> - struct intel_gvt_gtt_entry e;
> - unsigned long index;
> int ret;
>
> trace_spt_change(spt->vgpu->id, "die", spt,
> - spt->guest_page.gfn, spt->shadow_page.type);
> -
> + spt->guest_page.gfn, spt->shadow_page.type);
> if (ppgtt_put_spt(spt) > 0)
> return 0;
> + ret = ppgtt_invalidate_spt(spt);
> + if (!ret) {
> + trace_spt_change(spt->vgpu->id, "release", spt,
> + spt->guest_page.gfn, spt->shadow_page.type);
> + ppgtt_free_spt(spt);
> + }
> +
> + return ret;
> +}
> +
> +static int ppgtt_invalidate_spt(struct intel_vgpu_ppgtt_spt *spt)
> +{
> + struct intel_vgpu *vgpu = spt->vgpu;
> + struct intel_gvt_gtt_entry e;
> + unsigned long index;
> + int ret;
>
> for_each_present_shadow_entry(spt, &e, index) {
> switch (e.type) {
> @@ -1059,9 +1072,6 @@ static int ppgtt_invalidate_spt(struct intel_vgpu_ppgtt_spt *spt)
> }
> }
>
> - trace_spt_change(spt->vgpu->id, "release", spt,
> - spt->guest_page.gfn, spt->shadow_page.type);
> - ppgtt_free_spt(spt);
> return 0;
> fail:
> gvt_vgpu_err("fail: shadow page %p shadow entry 0x%llx type %d\n",
> @@ -1393,7 +1403,7 @@ 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_and_free_spt(s);
> if (ret)
> goto fail;
> } else {
> --
> 2.25.1
>
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