From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 045FDC3A59F for ; Thu, 29 Aug 2019 12:40:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D3D092339E for ; Thu, 29 Aug 2019 12:40:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727142AbfH2MkV (ORCPT ); Thu, 29 Aug 2019 08:40:21 -0400 Received: from mx1.redhat.com ([209.132.183.28]:56736 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725782AbfH2MkV (ORCPT ); Thu, 29 Aug 2019 08:40:21 -0400 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id A8CCC3083363; Thu, 29 Aug 2019 12:40:20 +0000 (UTC) Received: from gondolin (dhcp-192-222.str.redhat.com [10.33.192.222]) by smtp.corp.redhat.com (Postfix) with ESMTP id 0F6C66013A; Thu, 29 Aug 2019 12:40:15 +0000 (UTC) Date: Thu, 29 Aug 2019 14:40:13 +0200 From: Cornelia Huck To: Thomas Huth Cc: Christian Borntraeger , Janosch Frank , kvm@vger.kernel.org, David Hildenbrand , Heiko Carstens , Vasily Gorbik , linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] KVM: s390: Test for bad access register and size at the start of S390_MEM_OP Message-ID: <20190829144013.322edb0a.cohuck@redhat.com> In-Reply-To: <20190829122517.31042-1-thuth@redhat.com> References: <20190829122517.31042-1-thuth@redhat.com> Organization: Red Hat GmbH MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.44]); Thu, 29 Aug 2019 12:40:20 +0000 (UTC) Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Thu, 29 Aug 2019 14:25:17 +0200 Thomas Huth wrote: > If the KVM_S390_MEM_OP ioctl is called with an access register >= 16, > then there is certainly a bug in the calling userspace application. > We check for wrong access registers, but only if the vCPU was already > in the access register mode before (i.e. the SIE block has recorded > it). The check is also buried somewhere deep in the calling chain (in > the function ar_translation()), so this is somewhat hard to find. > > It's better to always report an error to the userspace in case this > field is set wrong, and it's safer in the KVM code if we block wrong > values here early instead of relying on a check somewhere deep down > the calling chain, so let's add another check to kvm_s390_guest_mem_op() > directly. > > We also should check that the "size" is non-zero here (thanks to Janosch > Frank for the hint!). If we do not check the size, we could call vmalloc() > with this 0 value, and this will cause a kernel warning. > > Signed-off-by: Thomas Huth > --- > v2: Check mop->size to be non-zero > > arch/s390/kvm/kvm-s390.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c > index f329dcb3f44c..49d7722229ae 100644 > --- a/arch/s390/kvm/kvm-s390.c > +++ b/arch/s390/kvm/kvm-s390.c > @@ -4255,7 +4255,7 @@ static long kvm_s390_guest_mem_op(struct kvm_vcpu *vcpu, > const u64 supported_flags = KVM_S390_MEMOP_F_INJECT_EXCEPTION > | KVM_S390_MEMOP_F_CHECK_ONLY; > > - if (mop->flags & ~supported_flags) > + if (mop->flags & ~supported_flags || mop->ar >= NUM_ACRS || !mop->size) > return -EINVAL; > > if (mop->size > MEM_OP_MAX_SIZE) Reviewed-by: Cornelia Huck