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SubjectRe: [PATCH 1/3] KVM: MMU: fix smap permission check


On 05/07/2015 05:32 PM, Paolo Bonzini wrote:
>
>
> On 07/05/2015 10:20, Xiao Guangrong wrote:
>> 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>
>> ---
>> 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 c7d6563..06eb2fc 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 fd49c86..6e6d115 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);
>>
>
> Applied.
>
> For the other patches I'm waiting for an answer re. kvm_mmu_pte_write.

Sure. Actually, i noticed these bugs when i was reviewing your patches,
will continue to review soon. :)


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