arm/arm64: KVM: Take mmap_sem in kvm_arch_prepare_memory_region

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: Eric Auger <eric.auger@rehat.com>
Cc: stable@vger.kernel.org # v3.18+
Reviewed-by: Christoffer Dall <cdall@linaro.org>
[ Handle dirty page logging failure case ]
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

1 files changed, 8 insertions, 3 deletions

diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
index f2e2e0c6d6fd..13b9c1fa8961 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;
 }