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From: Greg KH on 1 Jul 2010 17:30
2.6.34-stable review patch. If anyone has any objections, please let me know.

------------------

From: Avi Kivity <avi(a)redhat.com>

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(a)redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti(a)redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh(a)suse.de>

(Cherry-picked from commit 3dbe141595faa48a067add3e47bba3205b79d33c)
---
arch/x86/include/asm/kvm_host.h | 1 +
arch/x86/kvm/mmu.c | 3 ++-
2 files changed, 3 insertions(+), 1 deletion(-)

--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -180,6 +180,7 @@ union kvm_mmu_page_role {
unsigned invalid:1;
unsigned cr4_pge:1;
unsigned nxe:1;
+ unsigned cr0_wp:1;
};
};

--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -223,7 +223,7 @@ void kvm_mmu_set_mask_ptes(u64 user_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);
}
@@ -2439,6 +2439,7 @@ static int init_kvm_softmmu(struct kvm_v
r = paging32_init_context(vcpu);

vcpu->arch.mmu.base_role.glevels = vcpu->arch.mmu.root_level;
+ vcpu->arch.mmu.base_role.cr0_wp = is_write_protection(vcpu);

return r;
}


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