[PATCH 4.0 009/148] KVM: MMU: fix smap permission check

Greg Kroah-Hartman
2015-06-03T12:55:23Z

From: Xiao Guangrong <guangrong.xiao@linux.intel.com>

commit 7cbeed9bce7580479bb97457dad220cb3594b875 upstream.

Current permission check assumes that RSVD bit in PFEC is always zero,
however, it is not true since MMIO #PF will use it to quickly identify
MMIO access

Fix it by clearing the bit if walking guest page table is needed

Signed-off-by: Xiao Guangrong <guangrong.xiao@linux.intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/x86/kvm/mmu.h | 2 ++
arch/x86/kvm/paging_tmpl.h | 7 +++++++
2 files changed, 9 insertions(+)

--- a/arch/x86/kvm/mmu.h
+++ b/arch/x86/kvm/mmu.h
@@ -166,6 +166,8 @@ static inline bool permission_fault(stru
int index = (pfec >> 1) +
(smap >> (X86_EFLAGS_AC_BIT - PFERR_RSVD_BIT + 1));

+ WARN_ON(pfec & PFERR_RSVD_MASK);
+
return (mmu->permissions[index] >> pte_access) & 1;
}

--- a/arch/x86/kvm/paging_tmpl.h
+++ b/arch/x86/kvm/paging_tmpl.h
@@ -718,6 +718,13 @@ static int FNAME(page_fault)(struct kvm_
mmu_is_nested(vcpu));
if (likely(r != RET_MMIO_PF_INVALID))
return r;
+
+ /*
+ * page fault with PFEC.RSVD = 1 is caused by shadow
+ * page fault, should not be used to walk guest page
+ * table.
+ */
+ error_code &= ~PFERR_RSVD_MASK;
};

r = mmu_topup_memory_caches(vcpu);