On 12.09.19 12:58, David Hildenbrand wrote: > 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. Yes, lets also do the designated initializer, add more text to the patch description (or should we not?) add cc stable and I will pick a v2. > >> >> 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 >> > >
