On 12.09.19 11:20, Thomas Huth wrote: > On 12/09/2019 11.14, David Hildenbrand wrote: >> On 12.09.19 11:00, Thomas Huth wrote: >>> When the userspace program runs the KVM_S390_INTERRUPT ioctl to inject >>> an interrupt, we convert them from the legacy struct kvm_s390_interrupt >>> to the new struct kvm_s390_irq via the s390int_to_s390irq() function. >>> However, this function does not take care of all types of interrupts >>> that we can inject into the guest later (see do_inject_vcpu()). Since we >>> do not clear out the s390irq values before calling s390int_to_s390irq(), >>> there is a chance that we copy unwanted data from the kernel stack >>> into the guest memory later if the interrupt data has not been properly >>> initialized by s390int_to_s390irq(). >>> >>> Specifically, the problem exists with the KVM_S390_INT_PFAULT_INIT >>> interrupt: s390int_to_s390irq() does not handle it, but the function >>> __deliver_pfault_init() will later copy the uninitialized stack data >>> from the ext.ext_params2 into the guest memory. >>> >>> Fix it by handling that interrupt type in s390int_to_s390irq(), too. >>> And while we're at it, make sure that s390int_to_s390irq() now >>> directly returns -EINVAL for unknown interrupt types, so that we >>> do not run into this problem again in case we add more interrupt >>> types to do_inject_vcpu() sometime in the future. >>> >>> Signed-off-by: Thomas Huth <thuth@xxxxxxxxxx> >>> --- >>> arch/s390/kvm/interrupt.c | 10 ++++++++++ >>> 1 file changed, 10 insertions(+) >>> >>> diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c >>> index 3e7efdd9228a..165dea4c7f19 100644 >>> --- a/arch/s390/kvm/interrupt.c >>> +++ b/arch/s390/kvm/interrupt.c >>> @@ -1960,6 +1960,16 @@ int s390int_to_s390irq(struct kvm_s390_interrupt *s390int, >>> case KVM_S390_MCHK: >>> irq->u.mchk.mcic = s390int->parm64; >>> break; >>> + case KVM_S390_INT_PFAULT_INIT: >>> + irq->u.ext.ext_params = s390int->parm; >>> + irq->u.ext.ext_params2 = s390int->parm64; >>> + break; >>> + case KVM_S390_RESTART: >>> + case KVM_S390_INT_CLOCK_COMP: >>> + case KVM_S390_INT_CPU_TIMER: >>> + break; >>> + default: >>> + return -EINVAL; >>> } >>> return 0; >>> } >>> >> >> Wouldn't a safe fix be to initialize the struct to zero in the caller? > > That's of course possible, too. But that means that we always have to > zero out the whole structure, so that's a little bit more of overhead > (well, it likely doesn't matter for such a legacy ioctl). I would vote for doing this as well. > > But the more important question: Do we then still care of fixing the > PFAULT_INIT interrupt here? Since it requires a parameter, the "case > KVM_S390_INT_PFAULT_INIT:" part would be required here anyway. > That's indeed true. Reviewed-by: David Hildenbrand <david@xxxxxxxxxx> > Thomas > -- Thanks, David / dhildenb
