Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound

[pandora-kernel.git] / arch / s390 / kvm / priv.c

diff --git a/arch/s390/kvm/priv.c b/arch/s390/kvm/priv.c
index 3916263..d026389 100644 (file)
--- 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);