Re: [PATCH v4 01/29] drm/i915/gvt: Verify pfn is "valid" before dereferencing "struct page"

From: Wang, Zhi A
Date: Tue Aug 01 2023 - 07:23:30 EST

On 7/29/2023 4:35 AM, Sean Christopherson wrote:
Check that the pfn found by gfn_to_pfn() is actually backed by "struct
page" memory prior to retrieving and dereferencing the page. KVM
supports backing guest memory with VM_PFNMAP, VM_IO, etc., and so
there is no guarantee the pfn returned by gfn_to_pfn() has an associated
"struct page".

Fixes: b901b252b6cf ("drm/i915/gvt: Add 2M huge gtt support")
Reviewed-by: Yan Zhao <yan.y.zhao@xxxxxxxxx>
Tested-by: Yongwei Ma <>
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
drivers/gpu/drm/i915/gvt/gtt.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/drivers/gpu/drm/i915/gvt/gtt.c b/drivers/gpu/drm/i915/gvt/gtt.c
index 4ec85308379a..58b9b316ae46 100644
--- a/drivers/gpu/drm/i915/gvt/gtt.c
+++ b/drivers/gpu/drm/i915/gvt/gtt.c
@@ -1183,6 +1183,10 @@ static int is_2MB_gtt_possible(struct intel_vgpu *vgpu,
pfn = gfn_to_pfn(vgpu->vfio_device.kvm, ops->get_pfn(entry));
if (is_error_noslot_pfn(pfn))
return -EINVAL;
+ if (!pfn_valid(pfn))
+ return -EINVAL;
return PageTransHuge(pfn_to_page(pfn));

Reviewed-by: Zhi Wang <>