KVM: s390: avoid memory overwrites on emergency signal injection

commit b85de33a1a3433487b6a721cfdce25ec8673e622 upstream.

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>
Signed-off-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c
index ec18cd5a252908bba3c210dd3ff2192e15d25094..cbee788d9625126f569b2e8004fdb119418c3800 100644 (file)
--- a/arch/s390/kvm/interrupt.c
+++ b/arch/s390/kvm/interrupt.c
@@ -1130,6 +1130,10 @@ 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, 2);
 
+       /* 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_set_mask(CPUSTAT_EXT_INT, li->cpuflags);