Merge tag 'kvm-s390-20140825' of git://git.kernel.org/pub/scm/linux/kernel/git/kvms390/linux into HEAD

Here are two fixes for s390 KVM code that prevent:
1. a malicious user to trigger a kernel BUG
2. a malicious user to change the storage key of read-only pages

2 files changed, 10 insertions, 13 deletions

diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index a3c324ec4370..197bec03d919 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -1321,19 +1321,6 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
                 return -EINVAL;
         }
 
-        switch (kvm_run->exit_reason) {
-        case KVM_EXIT_S390_SIEIC:
-        case KVM_EXIT_UNKNOWN:
-        case KVM_EXIT_INTR:
-        case KVM_EXIT_S390_RESET:
-        case KVM_EXIT_S390_UCONTROL:
-        case KVM_EXIT_S390_TSCH:
-        case KVM_EXIT_DEBUG:
-                break;
-        default:
-                BUG();
-        }
-
         vcpu->arch.sie_block->gpsw.mask = kvm_run->psw_mask;
         vcpu->arch.sie_block->gpsw.addr = kvm_run->psw_addr;
         if (kvm_run->kvm_dirty_regs & KVM_SYNC_PREFIX) {
diff --git a/arch/s390/mm/pgtable.c b/arch/s390/mm/pgtable.c
index 19daa53a3da4..5404a6261db9 100644
--- a/arch/s390/mm/pgtable.c
+++ b/arch/s390/mm/pgtable.c
@@ -986,11 +986,21 @@ int set_guest_storage_key(struct mm_struct *mm, unsigned long addr,
         pte_t *ptep;
 
         down_read(&mm->mmap_sem);
+retry:
         ptep = get_locked_pte(current->mm, addr, &ptl);
         if (unlikely(!ptep)) {
                 up_read(&mm->mmap_sem);
                 return -EFAULT;
         }
+        if (!(pte_val(*ptep) & _PAGE_INVALID) &&
+             (pte_val(*ptep) & _PAGE_PROTECT)) {
+                        pte_unmap_unlock(*ptep, ptl);
+                        if (fixup_user_fault(current, mm, addr, FAULT_FLAG_WRITE)) {
+                                up_read(&mm->mmap_sem);
+                                return -EFAULT;
+                        }
+                        goto retry;
+                }
 
         new = old = pgste_get_lock(ptep);
         pgste_val(new) &= ~(PGSTE_GR_BIT | PGSTE_GC_BIT |