KVM: s390: avoid memory overwrites on emergency signal injection

Commit 383d0b050106 ("KVM: s390: handle pending local interrupts via
bitmap") introduced a possible memory overwrite from user space.

User space could pass an invalid emergency signal code (sending VCPU)
and therefore exceed the bitmap. Let's take care of this case and
check that the id is in the valid range.

Reviewed-by: Dominik Dingel <dingel@linux.vnet.ibm.com>
Cc: stable@vger.kernel.org # v3.19+ db27a7a KVM: Provide function for VCPU lookup by id
Signed-off-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c
index 373e32346d68..7242c2da4009 100644
--- a/arch/s390/kvm/interrupt.c
+++ b/arch/s390/kvm/interrupt.c
@@ -1110,6 +1110,10 @@ static int __inject_sigp_emergency(struct kvm_vcpu *vcpu,
         trace_kvm_s390_inject_vcpu(vcpu->vcpu_id, KVM_S390_INT_EMERGENCY,
                                    irq->u.emerg.code, 0);
 
+        /* sending vcpu invalid */
+        if (kvm_get_vcpu_by_id(vcpu->kvm, irq->u.emerg.code) == NULL)
+                return -EINVAL;
+
         set_bit(irq->u.emerg.code, li->sigp_emerg_pending);
         set_bit(IRQ_PEND_EXT_EMERGENCY, &li->pending_irqs);
         atomic_or(CPUSTAT_EXT_INT, li->cpuflags);