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(). You mean by using the migration callbacks to get all interrupts back to userspace? > > 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. Shouldnt we add some more detailed description how this can happen? Something like "By using the KVM_S390_INTERRUPT ioctl with a KVM_S390_INT_PFAULT_INIT interrupt followed by the KVM_S390_GET_IRQ_STATE ioctl the user can extract a value from the kernel stack." > > 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> Cc: stable Reviewed-by: Christian Borntraeger <borntraeger@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; > } >
