Patch "arm/arm64: KVM: Enforce Break-Before-Make on Stage-2 page tables" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

arm/arm64: KVM: Enforce Break-Before-Make on Stage-2 page tables

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
arm-arm64-kvm-enforce-break-before-make-on-stage-2-page-tables.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Marc Zyngier <[email protected]>
Date: Thu, 28 Apr 2016 16:16:31 +0100
Subject: arm/arm64: KVM: Enforce Break-Before-Make on Stage-2 page tables

From: Marc Zyngier <[email protected]>

commit d4b9e0790aa764c0b01e18d4e8d33e93ba36d51f upstream.

The ARM architecture mandates that when changing a page table entry from a valid entry to another valid entry, an invalid entry is first written, TLB invalidated, and only then the new entry being written.

The current code doesn't respect this, directly writing the new entry and only then invalidating TLBs. Let's fix it up.

---
 arch/arm/kvm/mmu.c |   17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

@@ -886,11 +886,14 @@ static int stage2_set_pmd_huge(struct kv
 	VM_BUG_ON(pmd_present(*pmd) && pmd_pfn(*pmd) != pmd_pfn(*new_pmd));
 
 	old_pmd = *pmd;
-	kvm_set_pmd(pmd, *new_pmd);
-	if (pmd_present(old_pmd))
+	if (pmd_present(old_pmd)) {
+		pmd_clear(pmd);
 		kvm_tlb_flush_vmid_ipa(kvm, addr);
-	else
+	} else {
 		get_page(virt_to_page(pmd));
+	}
+
+	kvm_set_pmd(pmd, *new_pmd);
 	return 0;
 }
 

@@ -939,12 +942,14 @@ static int stage2_set_pte(struct kvm *kv
 
 	/* Create 2nd stage page table mapping - Level 3 */
 	old_pte = *pte;
-	kvm_set_pte(pte, *new_pte);
-	if (pte_present(old_pte))
+	if (pte_present(old_pte)) {
+		kvm_set_pte(pte, __pte(0));
 		kvm_tlb_flush_vmid_ipa(kvm, addr);
-	else
+	} else {
 		get_page(virt_to_page(pte));
+	}
 
+	kvm_set_pte(pte, *new_pte);
 	return 0;
 }
 

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/arm-arm64-kvm-enforce-break-before-make-on-stage-2-page-tables.patch queue-4.4/kvm-arm64-fix-ec-field-in-inject_abt64.patch