[3.13.y.z extended stable] Patch "KVM: s390: Fix user triggerable bug in dead code" has been added to staging queue

Kamal Mostafa kamal at canonical.com
Tue Sep 30 21:29:42 UTC 2014

This is a note to let you know that I have just added a patch titled

    KVM: s390: Fix user triggerable bug in dead code

to the linux-3.13.y-queue branch of the 3.13.y.z extended stable tree 
which can be found at:


This patch is scheduled to be released in version

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.13.y.z tree, see



>From 144af6ec5fce29726a42756e76a31e295f939d5b Mon Sep 17 00:00:00 2001
From: Christian Borntraeger <borntraeger at de.ibm.com>
Date: Wed, 6 Aug 2014 16:17:58 +0200
Subject: KVM: s390: Fix user triggerable bug in dead code

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 at de.ibm.com>
Reviewed-by: Cornelia Huck <cornelia.huck at de.ibm.com>
Reviewed-by: David Hildenbrand <dahi at linux.vnet.ibm.com>
[ kamal: backport to 3.13-stable: context ]
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
 arch/s390/kvm/kvm-s390.c | 12 ------------
 1 file changed, 12 deletions(-)

diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index bfe7726..2480d92 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -802,18 +802,6 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)

 	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_S390_RESET:
-	case KVM_EXIT_S390_TSCH:
-		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) {

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