thanks, applied and queued for 5.3 (need to do some regression testing before sending out)

On 12.09.19 13:54, 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 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: David Hildenbrand david@redhat.com Reviewed-by: Christian Borntraeger borntraeger@de.ibm.com Signed-off-by: Thomas Huth thuth@redhat.com

---

arch/s390/kvm/interrupt.c | 10 ++++++++++ arch/s390/kvm/kvm-s390.c | 2 +- 2 files changed, 11 insertions(+), 1 deletion(-)

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;

} diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c index f329dcb3f44c..082eac2abc88 100644 --- a/arch/s390/kvm/kvm-s390.c +++ b/arch/s390/kvm/kvm-s390.c @@ -4323,7 +4323,7 @@ long kvm_arch_vcpu_async_ioctl(struct file *filp, } case KVM_S390_INTERRUPT: { struct kvm_s390_interrupt s390int;

• struct kvm_s390_irq s390irq;
  

• struct kvm_s390_irq s390irq = {};
  

if (copy_from_user(&s390int, argp, sizeof(s390int))) return -EFAULT;