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    Subject[PATCH 4.9 011/152] arm/arm64: KVM: Take mmap_sem in stage2_unmap_vm
    Date
    4.9-stable review patch.  If anyone has any objections, please let me know.

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

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

    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@linaro.org>
    Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
    Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    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);
    }


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