[PATCH 3.2 006/102] KVM: s390: Fix user triggerable bug in dead code

[Ben Hutchings]

3.2.64-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Christian Borntraeger <borntraeger@xxxxxxxxxx>

commit 614a80e474b227cace52fd6e3c790554db8a396e upstream.

In the early days, we had some special handling for the
KVM_EXIT_S390_SIEIC exit, but this was gone in 2009 with commit
d7b0b5eb3000 (KVM: s390: Make psw available on all exits, not
just a subset).

Now this switch statement is just a sanity check for userspace
not messing with the kvm_run structure. Unfortunately, this
allows userspace to trigger a kernel BUG. Let's just remove
this switch statement.

Signed-off-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>
Reviewed-by: Cornelia Huck <cornelia.huck@xxxxxxxxxx>
Reviewed-by: David Hildenbrand <dahi@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 arch/s390/kvm/kvm-s390.c | 13 -------------
 1 file changed, 13 deletions(-)

--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -516,16 +516,6 @@ rerun_vcpu:
 
 	BUG_ON(vcpu->kvm->arch.float_int.local_int[vcpu->vcpu_id] == NULL);
 
-	switch (kvm_run->exit_reason) {
-	case KVM_EXIT_S390_SIEIC:
-	case KVM_EXIT_UNKNOWN:
-	case KVM_EXIT_INTR:
-	case KVM_EXIT_S390_RESET:
-		break;
-	default:
-		BUG();
-	}
-
 	vcpu->arch.sie_block->gpsw.mask = kvm_run->psw_mask;
 	vcpu->arch.sie_block->gpsw.addr = kvm_run->psw_addr;
 

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