KVM: x86/xen: Fix cleanup logic in emulation of Xen schedop poll hypercalls

kvm_xen_schedop_poll does a kmalloc_array() when a VM polls the host
for more than one event channel potr (nr_ports > 1).

After the kmalloc_array(), the error paths need to go through the
"out" label, but the call to kvm_read_guest_virt() does not.

Fixes: 92c5896 ("KVM: x86/xen: Use kvm_read_guest_virt() instead of open-coding it badly")
Reviewed-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Manuel Andreas <manuel.andreas@tum.de>
[Adjusted commit message. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Author: styxs

arch/x86/kvm/xen.c

@@ -1526,7 +1526,7 @@ static bool kvm_xen_schedop_poll(struct kvm_vcpu *vcpu, bool longmode,
 	if (kvm_read_guest_virt(vcpu, (gva_t)sched_poll.ports, ports,
 				sched_poll.nr_ports * sizeof(*ports), &e)) {
 		*r = -EFAULT;
-		return true;
+		goto out;
 	}
 
 	for (i = 0; i < sched_poll.nr_ports; i++) {