• Thomas Huth's avatar
    KVM: s390: Do not leak kernel stack data in the KVM_S390_INTERRUPT ioctl · 53936b5b
    Thomas Huth authored
    
    
    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 random data from the kernel stack which
    could be leaked to the userspace later.
    
    Specifically, the problem exists with the KVM_S390_INT_PFAULT_INIT
    interrupt: s390int_to_s390irq() does not handle it, and the function
    __inject_pfault_init() later copies irq->u.ext which contains the
    random kernel stack data. This data can then be leaked either to
    the guest memory in __deliver_pfault_init(), or the userspace might
    retrieve it directly with the KVM_S390_GET_IRQ_STATE ioctl.
    
    Fix it by handling that interrupt type in s390int_to_s390irq(), too,
    and by making sure that the s390irq struct is properly pre-initialized.
    And while we're at it, make sure that s390int_to_s390irq() now
    directly returns -EINVAL for unknown interrupt types, so that we
    immediately get a proper error code in case we add more interrupt
    types to do_inject_vcpu() without updating s390int_to_s390irq()
    sometime in the future.
    
    Cc: stable@vger.kernel.org
    Reviewed-by: default avatarDavid Hildenbrand <david@redhat.com>
    Reviewed-by: default avatarChristian Borntraeger <borntraeger@de.ibm.com>
    Reviewed-by: default avatarJanosch Frank <frankja@linux.ibm.com>
    Signed-off-by: default avatarThomas Huth <thuth@redhat.com>
    Link: https://lore.kernel.org/kvm/20190912115438.25761-1-thuth@redhat.com
    
    Signed-off-by: default avatarChristian Borntraeger <borntraeger@de.ibm.com>
    53936b5b