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=-16.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT 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 B88C8C4338F for ; Wed, 28 Jul 2021 14:27:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A2A5E60F5E for ; Wed, 28 Jul 2021 14:27:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237160AbhG1O07 (ORCPT ); Wed, 28 Jul 2021 10:26:59 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:19490 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236979AbhG1O0p (ORCPT ); Wed, 28 Jul 2021 10:26:45 -0400 Received: from pps.filterd (m0098393.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.43/8.16.0.43) with SMTP id 16SENPiO052655; Wed, 28 Jul 2021 10:26:44 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=from : to : cc : subject : date : message-id : in-reply-to : references : mime-version : content-transfer-encoding; s=pp1; bh=pSD6iL4VbgZFGdwWWZaBv3AxV71jLUzQK3+a44HALS8=; b=NLlyYJE4hyLMKillLZ6kIHkiCkBFfQIIxZCIzK0snE7jtKOhuGlYqjI901rOikxh2bvg p371NXDsGv/VHOK+1S3AeX/vEb9Mx1IqPn+kduNAopwRTl9WFJXS291G4VVJJUC3CHe4 UvVTyToLvV5L06uhe0lCN9orIzI95S7G9pG1XeSvwlBzx+y9AqMWzdUj5smsfv0s4+df 9c/Y+qQiKKrhKlnI8yHLESOd/BCI2iruwPKEqeFNSMc3vmpdG5Rpyj/R4qqq5x0kfaMF PNDcHELTdGF6qti3c3T74NKvhuDRxL62WO75XJF/9hVc/69BS1pLsUEsFEc2dLMfPbpC Sg== Received: from pps.reinject (localhost [127.0.0.1]) by mx0a-001b2d01.pphosted.com with ESMTP id 3a38tere17-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 28 Jul 2021 10:26:43 -0400 Received: from m0098393.ppops.net (m0098393.ppops.net [127.0.0.1]) by pps.reinject (8.16.0.43/8.16.0.43) with SMTP id 16SENT29053225; Wed, 28 Jul 2021 10:26:43 -0400 Received: from ppma03ams.nl.ibm.com (62.31.33a9.ip4.static.sl-reverse.com [169.51.49.98]) by mx0a-001b2d01.pphosted.com with ESMTP id 3a38tere0b-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 28 Jul 2021 10:26:43 -0400 Received: from pps.filterd (ppma03ams.nl.ibm.com [127.0.0.1]) by ppma03ams.nl.ibm.com (8.16.1.2/8.16.1.2) with SMTP id 16SEJ87m024334; Wed, 28 Jul 2021 14:26:41 GMT Received: from b06cxnps4076.portsmouth.uk.ibm.com (d06relay13.portsmouth.uk.ibm.com [9.149.109.198]) by ppma03ams.nl.ibm.com with ESMTP id 3a235yh4k1-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 28 Jul 2021 14:26:41 +0000 Received: from d06av23.portsmouth.uk.ibm.com (d06av23.portsmouth.uk.ibm.com [9.149.105.59]) by b06cxnps4076.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 16SEQbru25821656 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 28 Jul 2021 14:26:37 GMT Received: from d06av23.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id BBEEEA4053; Wed, 28 Jul 2021 14:26:37 +0000 (GMT) Received: from d06av23.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 61189A4040; Wed, 28 Jul 2021 14:26:37 +0000 (GMT) Received: from localhost.localdomain (unknown [9.145.9.194]) by d06av23.portsmouth.uk.ibm.com (Postfix) with ESMTP; Wed, 28 Jul 2021 14:26:37 +0000 (GMT) From: Claudio Imbrenda To: kvm@vger.kernel.org Cc: cohuck@redhat.com, borntraeger@de.ibm.com, frankja@linux.ibm.com, thuth@redhat.com, pasic@linux.ibm.com, david@redhat.com, linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v2 02/13] KVM: s390: pv: leak the ASCE page when destroy fails Date: Wed, 28 Jul 2021 16:26:20 +0200 Message-Id: <20210728142631.41860-3-imbrenda@linux.ibm.com> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210728142631.41860-1-imbrenda@linux.ibm.com> References: <20210728142631.41860-1-imbrenda@linux.ibm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: 9xoDUcRIV-yvPjGk0GOmJo43ddEZ3al2 X-Proofpoint-ORIG-GUID: TruLFZDE12OHVgwNsCrzEq1RWVPbhflv X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391,18.0.790 definitions=2021-07-28_08:2021-07-27,2021-07-28 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 malwarescore=0 priorityscore=1501 impostorscore=0 spamscore=0 clxscore=1015 mlxlogscore=999 mlxscore=0 phishscore=0 adultscore=0 suspectscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2107140000 definitions=main-2107280079 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When a protected VM is created, the topmost level of page tables of its ASCE is marked by the Ultravisor; any attempt to use that memory for protected virtualization will result in failure. Only a successful Destroy Configuration UVC will remove the marking. When the Destroy Configuration UVC fails, the topmost level of page tables of the VM does not get its marking cleared; to avoid issues it must not be used again. Since the page becomes in practice unusable, we set it aside and leak it. Signed-off-by: Claudio Imbrenda --- arch/s390/kvm/pv.c | 53 +++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 52 insertions(+), 1 deletion(-) diff --git a/arch/s390/kvm/pv.c b/arch/s390/kvm/pv.c index e007df11a2fe..1ecdc1769ed9 100644 --- a/arch/s390/kvm/pv.c +++ b/arch/s390/kvm/pv.c @@ -155,6 +155,55 @@ static int kvm_s390_pv_alloc_vm(struct kvm *kvm) return -ENOMEM; } +/* + * Remove the topmost level of page tables from the list of page tables of + * the gmap. + * This means that it will not be freed when the VM is torn down, and needs + * to be handled separately by the caller, unless an intentional leak is + * intended. + */ +static void kvm_s390_pv_remove_old_asce(struct kvm *kvm) +{ + struct page *old; + + old = virt_to_page(kvm->arch.gmap->table); + list_del(&old->lru); + /* in case the ASCE needs to be "removed" multiple times */ + INIT_LIST_HEAD(&old->lru); +} + +/* + * Try to replace the current ASCE with another equivalent one. + * If the allocation of the new top level page table fails, the ASCE is not + * replaced. + * In any case, the old ASCE is removed from the list, therefore the caller + * has to make sure to save a pointer to it beforehands, unless an + * intentional leak is intended. + */ +static int kvm_s390_pv_replace_asce(struct kvm *kvm) +{ + unsigned long asce; + struct page *page; + void *table; + + kvm_s390_pv_remove_old_asce(kvm); + + page = alloc_pages(GFP_KERNEL_ACCOUNT, CRST_ALLOC_ORDER); + if (!page) + return -ENOMEM; + list_add(&page->lru, &kvm->arch.gmap->crst_list); + + table = page_to_virt(page); + memcpy(table, kvm->arch.gmap->table, 1UL << (CRST_ALLOC_ORDER + PAGE_SHIFT)); + + asce = (kvm->arch.gmap->asce & ~PAGE_MASK) | __pa(table); + WRITE_ONCE(kvm->arch.gmap->asce, asce); + WRITE_ONCE(kvm->mm->context.gmap_asce, asce); + WRITE_ONCE(kvm->arch.gmap->table, table); + + return 0; +} + /* this should not fail, but if it does, we must not free the donated memory */ int kvm_s390_pv_deinit_vm(struct kvm *kvm, u16 *rc, u16 *rrc) { @@ -169,9 +218,11 @@ int kvm_s390_pv_deinit_vm(struct kvm *kvm, u16 *rc, u16 *rrc) atomic_set(&kvm->mm->context.is_protected, 0); KVM_UV_EVENT(kvm, 3, "PROTVIRT DESTROY VM: rc %x rrc %x", *rc, *rrc); WARN_ONCE(cc, "protvirt destroy vm failed rc %x rrc %x", *rc, *rrc); - /* Inteded memory leak on "impossible" error */ + /* Intended memory leak on "impossible" error */ if (!cc) kvm_s390_pv_dealloc_vm(kvm); + else + kvm_s390_pv_replace_asce(kvm); return cc ? -EIO : 0; } -- 2.31.1