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

[Suzuki K Poulose]

From: Marc Zyngier <marc.zyng...@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.biesheu...@linaro.org>
Cc: Christoffer Dall <christoffer.d...@linaro.org>
Cc: Eric Auger <eric.au...@rehat.com>
Cc: sta...@vger.kernel.org # v3.18+
Signed-off-by: Marc Zyngier <marc.zyng...@arm.com>
[ Handle dirty page logging failure case ]
Signed-off-by: Suzuki K Poulose <suzuki.poul...@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