When cr0.wp=0, we may shadow a gpte having u/s=1 and r/w=0 with an spte
having u/s=0 and r/w=1. This allows excessive access if the guest sets
cr0.wp=1 and accesses through this spte.
Fix by making cr0.wp part of the base role; we'll have different sptes for
the two cases and the problem disappears.
Signed-off-by: Avi Kivity <avi@xxxxxxxxxx>
---
Documentation/kvm/mmu.txt | 2 ++
arch/x86/include/asm/kvm_host.h | 1 +
arch/x86/kvm/mmu.c | 3 ++-
3 files changed, 5 insertions(+), 1 deletions(-)
diff --git a/Documentation/kvm/mmu.txt b/Documentation/kvm/mmu.txt
index 0cc28fb..aaed6ab 100644
--- a/Documentation/kvm/mmu.txt
+++ b/Documentation/kvm/mmu.txt
@@ -163,6 +163,8 @@ Shadow pages contain the following information:
32-bit or 64-bit gptes are in use).
role.cr4_nxe:
Contains the value of efer.nxe for which the page is valid.
+ role.cr0_wp:
+ Contains the value of cr0.wp for which the page is valid.
gfn:
Either the guest page table containing the translations shadowed by this
page, or the base page frame for linear translations. See role.direct.
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index ed48904..2ca1867 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -179,6 +179,7 @@ union kvm_mmu_page_role {
unsigned access:3;
unsigned invalid:1;
unsigned nxe:1;
+ unsigned cr0_wp:1;
};
};
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 95bee9d..d3079eb 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -217,7 +217,7 @@ void kvm_mmu_set_mask_ptes(u64 user_mask, u64 accessed_mask,
}
EXPORT_SYMBOL_GPL(kvm_mmu_set_mask_ptes);
-static int is_write_protection(struct kvm_vcpu *vcpu)
+static bool is_write_protection(struct kvm_vcpu *vcpu)
{
return kvm_read_cr0_bits(vcpu, X86_CR0_WP);
}
@@ -2433,6 +2433,7 @@ static int init_kvm_softmmu(struct kvm_vcpu *vcpu)
r = paging32_init_context(vcpu);
vcpu->arch.mmu.base_role.cr4_pae = !!is_pae(vcpu);
+ vcpu->arch.mmu.base_role.cr0_wp = is_write_protection(vcpu);
return r;
}
--
1.7.0.4
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