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

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Message-ID: <20230729013535.1070024-2-seanjc@google.com>
Date:   Fri, 28 Jul 2023 18:35:07 -0700
From:   Sean Christopherson <seanjc@...gle.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Zhenyu Wang <zhenyuw@...ux.intel.com>,
        Zhi Wang <zhi.a.wang@...el.com>
Cc:     kvm@...r.kernel.org, intel-gvt-dev@...ts.freedesktop.org,
        intel-gfx@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Yan Zhao <yan.y.zhao@...el.com>,
        Yongwei Ma <yongwei.ma@...el.com>,
        Ben Gardon <bgardon@...gle.com>
Subject: [PATCH v4 01/29] drm/i915/gvt: Verify pfn is "valid" before
 dereferencing "struct page"

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@...el.com>
Tested-by: Yongwei Ma <yongwei.ma@...el.com>
Signed-off-by: Sean Christopherson <seanjc@...gle.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));
 }
 
-- 
2.41.0.487.g6d72f3e995-goog