From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:30470 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730907AbfILKrW (ORCPT ); Thu, 12 Sep 2019 06:47:22 -0400 Received: from pps.filterd (m0098410.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id x8CAhsiI081619 for ; Thu, 12 Sep 2019 06:47:21 -0400 Received: from e06smtp02.uk.ibm.com (e06smtp02.uk.ibm.com [195.75.94.98]) by mx0a-001b2d01.pphosted.com with ESMTP id 2uyhn6px2j-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Thu, 12 Sep 2019 06:47:21 -0400 Received: from localhost by e06smtp02.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Thu, 12 Sep 2019 11:47:19 +0100 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: Christian Borntraeger Date: Thu, 12 Sep 2019 12:47:13 +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: 8bit Message-Id: <4ed0c815-c598-bb0f-9841-d579fc62877f@de.ibm.com> Sender: linux-s390-owner@vger.kernel.org List-ID: To: Thomas Huth , Janosch Frank , kvm@vger.kernel.org Cc: David Hildenbrand , 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(). 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 Cc: stable Reviewed-by: Christian Borntraeger > --- > 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; > } >