On 12/09/2019 12.47, Christian Borntraeger 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(). > > You mean by using the migration callbacks to get all interrupts back to > userspace? Oh, I was not thinking about GET_IRQ_STATE yet, I was thinking about __deliver_pfault_init() which would deliver the value into the guest memory (from where the userspace program could extract it again). >> 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." GET_IRQ_STATE certainly deserves to be mentioned here, I'll add it to the patch description and will send a v2. Thomas
