linux-kernel - [PATCH v2 1/3] kvm: arm/arm64: Take mmap_sem in stage2_unmap

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Date:   Thu, 16 Mar 2017 18:20:49 +0000
From:   Suzuki K Poulose <suzuki.poulose@....com>
To:     linux-arm-kernel@...ts.infradead.org, andreyknvl@...gle.com
Cc:     dvyukov@...gle.com, marc.zyngier@....com,
        christoffer.dall@...aro.org, kvmarm@...ts.cs.columbia.edu,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org, kcc@...gle.com,
        syzkaller@...glegroups.com, will.deacon@....com,
        catalin.marinas@....com, pbonzini@...hat.com, mark.rutland@....com,
        suzuki.poulose@....com, ard.biesheuvel@...aro.org,
        stable@...r.kernel.org
Subject: [PATCH v2 1/3] kvm: arm/arm64: Take mmap_sem in stage2_unmap_vm

From: Marc Zyngier <marc.zyngier@....com>

We don't hold the mmap_sem while searching for the VMAs when
we try to unmap each memslot for a VM. Fix this properly to
avoid unexpected results.

Fixes: commit 957db105c997 ("arm/arm64: KVM: Introduce stage2_unmap_vm")
Cc: stable@...r.kernel.org # v3.19+
Reviewed-by: Christoffer Dall <cdall@...aro.org>
Signed-off-by: Marc Zyngier <marc.zyngier@....com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>
---
 arch/arm/kvm/mmu.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
index 962616f..f2e2e0c 100644
--- a/arch/arm/kvm/mmu.c
+++ b/arch/arm/kvm/mmu.c
@@ -803,6 +803,7 @@ void stage2_unmap_vm(struct kvm *kvm)
 	int idx;
 
 	idx = srcu_read_lock(&kvm->srcu);
+	down_read(&current->mm->mmap_sem);
 	spin_lock(&kvm->mmu_lock);
 
 	slots = kvm_memslots(kvm);
@@ -810,6 +811,7 @@ void stage2_unmap_vm(struct kvm *kvm)
 		stage2_unmap_memslot(kvm, memslot);
 
 	spin_unlock(&kvm->mmu_lock);
+	up_read(&current->mm->mmap_sem);
 	srcu_read_unlock(&kvm->srcu, idx);
 }
 
-- 
2.7.4