From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com ([209.132.183.28]:46784 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730434AbfILJOO (ORCPT ); Thu, 12 Sep 2019 05:14:14 -0400 Subject: Re: [PATCH] KVM: s390: Do not leak kernel stack data in the KVM_S390_INTERRUPT ioctl References: <20190912090050.20295-1-thuth@redhat.com> From: David Hildenbrand Message-ID: <6905df78-95f0-3d6d-aaae-910cd2d7a232@redhat.com> Date: Thu, 12 Sep 2019 11:14:11 +0200 MIME-Version: 1.0 In-Reply-To: <20190912090050.20295-1-thuth@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-s390-owner@vger.kernel.org List-ID: To: Thomas Huth , Christian Borntraeger , Janosch Frank , kvm@vger.kernel.org Cc: Cornelia Huck , linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org 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 > --- > 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? -- Thanks, David / dhildenb