From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:32966 "EHLO mx0b-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727373AbhADPZD (ORCPT ); Mon, 4 Jan 2021 10:25:03 -0500 Date: Mon, 4 Jan 2021 14:58:02 +0100 From: Claudio Imbrenda Subject: Re: [PATCH v1 1/4] s390/kvm: VSIE: stop leaking host addresses Message-ID: <20210104145802.7a2274a2@ibm-vm> In-Reply-To: References: <20201218141811.310267-1-imbrenda@linux.ibm.com> <20201218141811.310267-2-imbrenda@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit List-ID: To: David Hildenbrand Cc: linux-kernel@vger.kernel.org, borntraeger@de.ibm.com, frankja@linux.ibm.com, kvm@vger.kernel.org, linux-s390@vger.kernel.org, stable@vger.kernel.org On Sun, 20 Dec 2020 10:44:56 +0100 David Hildenbrand wrote: > On 18.12.20 15:18, Claudio Imbrenda wrote: > > The addresses in the SIE control block of the host should not be > > forwarded to the guest. They are only meaningful to the host, and > > moreover it would be a clear security issue. > > It's really almost impossible for someone without access to > documentation to understand what we leak. I assume we're leaking the > g1 address of a page table (entry), used for translation of g2->g3 to > g1. Can you try making that clearer? this is correct. I guess I can improve the text of the commit > In that case, it's pretty much a random number (of a random page used > as a leave page table) and does not let g1 identify locations of > symbols etc. If so, I don't think this is a "clear security issue" > and suggest squashing this into the actual fix (#p4 I assume). yeah __maybe__ I overstated the importance ;) But I would still like to keep it as a separate patch, looks more straightforward to me > @Christian, @Janosch? Am I missing something? > > > > > Subsequent patches will actually put the right values in the guest > > SIE control block. > > > > Fixes: a3508fbe9dc6d ("KVM: s390: vsie: initial support for nested > > virtualization") Cc: stable@vger.kernel.org > > Signed-off-by: Claudio Imbrenda > > --- > > arch/s390/kvm/vsie.c | 5 ----- > > 1 file changed, 5 deletions(-) > > > > diff --git a/arch/s390/kvm/vsie.c b/arch/s390/kvm/vsie.c > > index 4f3cbf6003a9..ada49583e530 100644 > > --- a/arch/s390/kvm/vsie.c > > +++ b/arch/s390/kvm/vsie.c > > @@ -416,11 +416,6 @@ static void unshadow_scb(struct kvm_vcpu > > *vcpu, struct vsie_page *vsie_page) memcpy((void *)((u64)scb_o + > > 0xc0), (void *)((u64)scb_s + 0xc0), 0xf0 - 0xc0); > > break; > > - case ICPT_PARTEXEC: > > - /* MVPG only */ > > - memcpy((void *)((u64)scb_o + 0xc0), > > - (void *)((u64)scb_s + 0xc0), 0xd0 - 0xc0); > > - break; > > } > > > > if (scb_s->ihcpu != 0xffffU) > > > >