linux-kernel - [PATCH] KVM: arm/arm64: Check pagesize when allocating a hugepage at Stage 2

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Message-Id: <20180104182433.3790-1-punit.agrawal@arm.com>
Date:   Thu,  4 Jan 2018 18:24:33 +0000
From:   Punit Agrawal <punit.agrawal@....com>
To:     kvmarm@...ts.cs.columbia.edu
Cc:     Punit Agrawal <punit.agrawal@....com>,
        linux-kernel@...r.kernel.org,
        Christoffer Dall <christoffer.dall@...aro.org>,
        Marc Zyngier <marc.zyngier@....com>
Subject: [PATCH] KVM: arm/arm64: Check pagesize when allocating a hugepage at Stage 2

KVM only supports PMD hugepages at stage 2 but doesn't actually check
that the provided hugepage memory pagesize is PMD_SIZE before populating
stage 2 entries.

In cases where the backing hugepage size is smaller than PMD_SIZE (such
as when using contiguous hugepages), KVM can end up creating stage 2
mappings that extend beyond the supplied memory.

Fix this by checking for the pagesize of userspace vma before creating
PMD hugepage at stage 2.

Fixes: ad361f093c1e31d ("KVM: ARM: Support hugetlbfs backed huge pages")
Signed-off-by: Punit Agrawal <punit.agrawal@....com>
Cc: Christoffer Dall <christoffer.dall@...aro.org>
Cc: Marc Zyngier <marc.zyngier@....com>
---
 virt/kvm/arm/mmu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c
index b4b69c2d1012..9dea96380339 100644
--- a/virt/kvm/arm/mmu.c
+++ b/virt/kvm/arm/mmu.c
@@ -1310,7 +1310,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 		return -EFAULT;
 	}
 
-	if (is_vm_hugetlb_page(vma) && !logging_active) {
+	if (vma_kernel_pagesize(vma) == PMD_SIZE && !logging_active) {
 		hugetlb = true;
 		gfn = (fault_ipa & PMD_MASK) >> PAGE_SHIFT;
 	} else {
-- 
2.15.1