[Intel-gfx] [PATCH v3 01/28] drm/i915/gvt: Verify pfn is "valid" before dereferencing "struct page"

[Sean Christopherson]

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.z...@intel.com>
Signed-off-by: Sean Christopherson <sea...@google.com>
---
 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));
 }
 
-- 
2.40.1.606.ga4b1b128d6-goog