KVM: arm64: Don't inherit exec permission across page-table levels (b757b47a) · Commits · 戴 / test

If a stage-2 page-table contains an executable, read-only mapping at the pte level (e.g. due to dirty logging being enabled), a subsequent write fault to the same page which tries to install a larger block mapping (e.g. due to dirty logging having been disabled) will erroneously inherit the exec permission and consequently skip I-cache invalidation for the rest of the block. Ensure that exec permission is only inherited by write faults when the new mapping is of the same size as the existing one. A subsequent instruction abort will result in I-cache invalidation for the entire block mapping. Signed-off-by:

Will Deacon <will@kernel.org> Signed-off-by:

Marc Zyngier <maz@kernel.org> Tested-by:

Quentin Perret <qperret@google.com> Reviewed-by:

Quentin Perret <qperret@google.com> Cc: Marc Zyngier <maz@kernel.org> Cc: <stable@vger.kernel.org> Link: https://lore.kernel.org/r/20200723101714.15873-1-will@kernel.org

arch/arm64/kvm/mmu.c

+6 −5

Original line number	Diff line number	Diff line
		@@ -1326,7 +1326,7 @@ static bool stage2_get_leaf_entry(struct kvm *kvm, phys_addr_t addr,
		return true;
		}

		static bool stage2_is_exec(struct kvm *kvm, phys_addr_t addr)
		static bool stage2_is_exec(struct kvm *kvm, phys_addr_t addr, unsigned long sz)
		{
		pud_t *pudp;
		pmd_t *pmdp;
		@@ -1338,11 +1338,11 @@ static bool stage2_is_exec(struct kvm *kvm, phys_addr_t addr)
		return false;

		if (pudp)
		return kvm_s2pud_exec(pudp);
		return sz <= PUD_SIZE && kvm_s2pud_exec(pudp);
		else if (pmdp)
		return kvm_s2pmd_exec(pmdp);
		return sz <= PMD_SIZE && kvm_s2pmd_exec(pmdp);
		else
		return kvm_s2pte_exec(ptep);
		return sz == PAGE_SIZE && kvm_s2pte_exec(ptep);
		}

		static int stage2_set_pte(struct kvm kvm, struct kvm_mmu_memory_cache cache,
		@@ -1958,7 +1958,8 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
		* execute permissions, and we preserve whatever we have.
		*/
		needs_exec = exec_fault \|\|
		(fault_status == FSC_PERM && stage2_is_exec(kvm, fault_ipa));
		(fault_status == FSC_PERM &&
		stage2_is_exec(kvm, fault_ipa, vma_pagesize));

		if (vma_pagesize == PUD_SIZE) {
		pud_t new_pud = kvm_pfn_pud(pfn, mem_type);

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