[PATCH 4.9 011/152] arm/arm64: KVM: Take mmap_sem in stage2_unmap_vm

From: Greg Kroah-Hartman
Date: Mon Apr 10 2017 - 13:55:36 EST


4.9-stable review patch. If anyone has any objections, please let me know.

------------------

From: Marc Zyngier <marc.zyngier@xxxxxxx>

commit 90f6e150e44a0dc3883110eeb3ab35d1be42b6bb upstream.

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")
Reviewed-by: Christoffer Dall <cdall@xxxxxxxxxx>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
arch/arm/kvm/mmu.c | 2 ++
1 file changed, 2 insertions(+)

--- 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);
}