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>

diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c
index 373e32346d68d6c3ae270ca39b96b09fe66b0a6e..7242c2da40095a32670fdf913d1f74fe1b2e1dd8 100644 (file)
--- 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);