From: Marc Zyngier <marc.zyngier@arm.com>
Date: Thu, 16 Mar 2017 18:20:49 +0000 (+0000)
Subject: arm/arm64: KVM: Take mmap_sem in stage2_unmap_vm
X-Git-Tag: release-20171130_firefly~4^2~100^2~1^2~15^2~24
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=8e88806117e4868bc459a3042e55f8bf06c0b9e0;p=firefly-linux-kernel-4.4.55.git

arm/arm64: KVM: Take mmap_sem in stage2_unmap_vm

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>
---

diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
index 11b6595c2672..5366a736151e 100644
--- a/arch/arm/kvm/mmu.c
+++ b/arch/arm/kvm/mmu.c
@@ -796,6 +796,7 @@ 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);
@@ -803,6 +804,7 @@ 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);
 }