[bug report] kvm: mmu: Don't expose private memslots to L2

[Dan Carpenter <dan.carpenter@xxxxxxxxxx>]

Hello Jim Mattson,

The patch 3a2936dedd20: "kvm: mmu: Don't expose private memslots to
L2" from May 9, 2018, leads to the following static checker warning:

	arch/x86/kvm/mmu/mmu.c:3686 nonpaging_map()
	error: uninitialized symbol 'map_writable'.

arch/x86/kvm/mmu/mmu.c
  3665  
  3666          if (fast_page_fault(vcpu, v, level, error_code))
  3667                  return RET_PF_RETRY;
  3668  
  3669          mmu_seq = vcpu->kvm->mmu_notifier_seq;
  3670          smp_rmb();
  3671  
  3672          if (try_async_pf(vcpu, prefault, gfn, v, &pfn, write, &map_writable))
                                                                      ^^^^^^^^^^^^^
The patch introduces a new false return which doesn't initialize
map_writable.

  3673                  return RET_PF_RETRY;
  3674  
  3675          if (handle_abnormal_pfn(vcpu, v, gfn, pfn, ACC_ALL, &r))
  3676                  return r;
  3677  
  3678          r = RET_PF_RETRY;
  3679          spin_lock(&vcpu->kvm->mmu_lock);
  3680          if (mmu_notifier_retry(vcpu->kvm, mmu_seq))
  3681                  goto out_unlock;
  3682          if (make_mmu_pages_available(vcpu) < 0)
  3683                  goto out_unlock;
  3684          if (likely(!force_pt_level))
  3685                  transparent_hugepage_adjust(vcpu, gfn, &pfn, &level);
  3686          r = __direct_map(vcpu, v, write, map_writable, level, pfn,
                                                 ^^^^^^^^^^^^

  3687                           prefault, false);
  3688  out_unlock:
  3689          spin_unlock(&vcpu->kvm->mmu_lock);
  3690          kvm_release_pfn_clean(pfn);
  3691          return r;

regards,
dan carpenter