Patch "arm/arm64: KVM: Enforce Break-Before-Make on Stage-2 page tables" has been added to the 4.5-stable tree

gregkh
2016-05-29T21:42:51Z

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 4.5-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-4.5 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.

>From d4b9e0790aa764c0b01e18d4e8d33e93ba36d51f Mon Sep 17 00:00:00 2001
From: Marc Zyngier <marc.zyngier@arm.com>
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 <marc.zyngier@arm.com>

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.

Reported-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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

--- a/arch/arm/kvm/mmu.c
+++ b/arch/arm/kvm/mmu.c
@@ -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 marc.zyngier@arm.com are

queue-4.5/arm-arm64-kvm-enforce-break-before-make-on-stage-2-page-tables.patch
queue-4.5/kvm-arm64-fix-ec-field-in-inject_abt64.patch