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[PATCH 3.18 070/124] arm/arm64: KVM: Take mmap_sem in kvm_arch_prepare_memory_region




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

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

From: Marc Zyngier <marc.zyngier@xxxxxxx>

commit 72f310481a08db821b614e7b5d00febcc9064b36 upstream.

We don't hold the mmap_sem while searching for VMAs (via find_vma), in
kvm_arch_prepare_memory_region, which can end up in expected failures.

Fixes: commit 8eef91239e57 ("arm/arm64: KVM: map MMIO regions at creation time")
Cc: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
Cc: Eric Auger <eric.auger@xxxxxxxxx>
Reviewed-by: Christoffer Dall <cdall@xxxxxxxxxx>
[ Handle dirty page logging failure case ]
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 |    3 +++
 1 file changed, 3 insertions(+)

--- a/arch/arm/kvm/mmu.c
+++ b/arch/arm/kvm/mmu.c
@@ -1407,6 +1407,7 @@ int kvm_arch_prepare_memory_region(struc
 	    (KVM_PHYS_SIZE >> PAGE_SHIFT))
 		return -EFAULT;
 
+	down_read(&current->mm->mmap_sem);
 	/*
 	 * A memory region could potentially cover multiple VMAs, and any holes
 	 * between them, so iterate over all of them to find out if we can map
@@ -1464,6 +1465,8 @@ int kvm_arch_prepare_memory_region(struc
 	else
 		stage2_flush_memslot(kvm, memslot);
 	spin_unlock(&kvm->mmu_lock);
+
+	up_read(&current->mm->mmap_sem);
 	return ret;
 }