From ceee7df749da03fa17ab5dc7d06dffb4980a32db Mon Sep 17 00:00:00 2001 From: Xiao Guangrong Date: Thu, 7 May 2015 16:20:15 +0800 Subject: [PATCH] KVM: MMU: fix smap permission check 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 Signed-off-by: Paolo Bonzini --- arch/x86/kvm/mmu.h | 2 ++ arch/x86/kvm/paging_tmpl.h | 7 +++++++ 2 files changed, 9 insertions(+) diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h index c7d65637c851..06eb2fc1bab8 100644 --- a/arch/x86/kvm/mmu.h +++ b/arch/x86/kvm/mmu.h @@ -166,6 +166,8 @@ static inline bool permission_fault(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu, 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; } diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h index fd49c867b25a..6e6d115fe9b5 100644 --- 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_vcpu *vcpu, gva_t addr, u32 error_code, 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);