1 files changed, 8 insertions, 2 deletions

diff --git a/arch/s390/kvm/priv.c b/arch/s390/kvm/priv.c
index 391626361084..d02638959922 100644
--- a/arch/s390/kvm/priv.c
+++ b/arch/s390/kvm/priv.c
@@ -336,6 +336,7 @@ static int handle_tprot(struct kvm_vcpu *vcpu)
         u64 address1 = disp1 + base1 ? vcpu->arch.guest_gprs[base1] : 0;
         u64 address2 = disp2 + base2 ? vcpu->arch.guest_gprs[base2] : 0;
         struct vm_area_struct *vma;
+        unsigned long user_address;
 
         vcpu->stat.instruction_tprot++;
 
@@ -349,9 +350,14 @@ static int handle_tprot(struct kvm_vcpu *vcpu)
                 return -EOPNOTSUPP;
 
 
+        /* we must resolve the address without holding the mmap semaphore.
+         * This is ok since the userspace hypervisor is not supposed to change
+         * the mapping while the guest queries the memory. Otherwise the guest
+         * might crash or get wrong info anyway. */
+        user_address = (unsigned long) __guestaddr_to_user(vcpu, address1);
+
         down_read(&current->mm->mmap_sem);
-        vma = find_vma(current->mm,
-                        (unsigned long) __guestaddr_to_user(vcpu, address1));
+        vma = find_vma(current->mm, user_address);
         if (!vma) {
                 up_read(&current->mm->mmap_sem);
                 return kvm_s390_inject_program_int(vcpu, PGM_ADDRESSING);