[PATCH 2/3] kvm: arm/arm64: Take mmap_sem in kvm_arch_prepare_memory_region

Suzuki K Poulose
2017-03-14T14:52:33Z

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

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@linaro.org>
Cc: Christoffer Dall <christoffer.dall@linaro.org>
Cc: Eric Auger <eric.auger@rehat.com>
Cc: stable@vger.kernel.org # v3.18+
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
[ Handle dirty page logging failure case ]
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
---
arch/arm/kvm/mmu.c | 11 ++++++++---
1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
index f2e2e0c..13b9c1f 100644
--- a/arch/arm/kvm/mmu.c
+++ b/arch/arm/kvm/mmu.c
@@ -1803,6 +1803,7 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
(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
@@ -1846,8 +1847,10 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
pa += vm_start - vma->vm_start;

/* IO region dirty page logging not allowed */
- if (memslot->flags & KVM_MEM_LOG_DIRTY_PAGES)
- return -EINVAL;
+ if (memslot->flags & KVM_MEM_LOG_DIRTY_PAGES) {
+ ret = -EINVAL;
+ goto out;
+ }

ret = kvm_phys_addr_ioremap(kvm, gpa, pa,
vm_end - vm_start,
@@ -1859,7 +1862,7 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
} while (hva < reg_end);

if (change == KVM_MR_FLAGS_ONLY)
- return ret;
+ goto out;

spin_lock(&kvm->mmu_lock);
if (ret)
@@ -1867,6 +1870,8 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
else
stage2_flush_memslot(kvm, memslot);
spin_unlock(&kvm->mmu_lock);
+out:
+ up_read(&current->mm->mmap_sem);
return ret;
}

--
2.7.4