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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B8150C433F5 for ; Tue, 22 Mar 2022 15:32:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238543AbiCVPdo (ORCPT ); Tue, 22 Mar 2022 11:33:44 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46640 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237504AbiCVPdm (ORCPT ); Tue, 22 Mar 2022 11:33:42 -0400 Received: from mx0b-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com [148.163.158.5]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AC86A82D1B; Tue, 22 Mar 2022 08:32:14 -0700 (PDT) Received: from pps.filterd (m0098421.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.1.2/8.16.1.2) with SMTP id 22MFJOWR025803; Tue, 22 Mar 2022 15:32:14 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=from : to : cc : subject : date : message-id : mime-version : content-transfer-encoding; s=pp1; bh=EzCy9QqoK8aDCpZvzNCryR+3SBEwvODW6uUXG8KKtjs=; b=GxUuj4M6jI+n13Ui+a/bsQO5vx1dmwLBCl3q2wbbYWOL9TcAXs2N/MagEcDs9z5Zq0Ks vXMgvwrtf75jo9heKv+VTzLGk4RO6oVABIOMlecneWxzugoTORUJLpbTuvchIyRq31eZ OUHkC10dr727Ux7X4049M/xvS0ZOwj6kkTEQiwLoeQDDhxmZFokRnm/MVi1Yi4YvOVUH +v4lAx9Ax6mxhCK+RpQjojLNZgfPYEdizR+zkLVVz/LyFet+2tQ6WA9TBS5vWDM+X68S 8uk8pUh2SEg17/p7n/9yPXP0HBAM2hRX0Wpf9cdF1lrMZddYD2tiRPYBrXVLyoZbwqzl 9g== Received: from pps.reinject (localhost [127.0.0.1]) by mx0a-001b2d01.pphosted.com with ESMTP id 3eyautshys-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 22 Mar 2022 15:32:13 +0000 Received: from m0098421.ppops.net (m0098421.ppops.net [127.0.0.1]) by pps.reinject (8.16.0.43/8.16.0.43) with SMTP id 22MFJOxi025687; Tue, 22 Mar 2022 15:32:13 GMT 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 3eyautshy5-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 22 Mar 2022 15:32:13 +0000 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 22MFTGA6001232; Tue, 22 Mar 2022 15:32:11 GMT Received: from b06cxnps4075.portsmouth.uk.ibm.com (d06relay12.portsmouth.uk.ibm.com [9.149.109.197]) by ppma03ams.nl.ibm.com with ESMTP id 3ew6t8xgpm-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 22 Mar 2022 15:32:11 +0000 Received: from d06av22.portsmouth.uk.ibm.com (d06av22.portsmouth.uk.ibm.com [9.149.105.58]) by b06cxnps4075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 22MFW87B27066822 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 22 Mar 2022 15:32:08 GMT Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 27E204C052; Tue, 22 Mar 2022 15:32:08 +0000 (GMT) Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id C56514C040; Tue, 22 Mar 2022 15:32:07 +0000 (GMT) Received: from tuxmaker.boeblingen.de.ibm.com (unknown [9.152.85.9]) by d06av22.portsmouth.uk.ibm.com (Postfix) with ESMTP; Tue, 22 Mar 2022 15:32:07 +0000 (GMT) From: Janis Schoetterl-Glausch To: Christian Borntraeger , Janosch Frank , Claudio Imbrenda , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Janis Schoetterl-Glausch Cc: David Hildenbrand , Sven Schnelle , kvm@vger.kernel.org, linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] KVM: s390: Fix lockdep issue in vm memop Date: Tue, 22 Mar 2022 16:32:04 +0100 Message-Id: <20220322153204.2637400-1-scgl@linux.ibm.com> X-Mailer: git-send-email 2.32.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: MhqFlwEUswo9YzQCOGLTpRB3_EH8CH7A X-Proofpoint-ORIG-GUID: mMJXVzBI4J81vBVOo9wGKqtRbSV9bWyD X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.850,Hydra:6.0.425,FMLib:17.11.64.514 definitions=2022-03-22_06,2022-03-22_01,2022-02-23_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 mlxlogscore=999 priorityscore=1501 mlxscore=0 malwarescore=0 bulkscore=0 adultscore=0 lowpriorityscore=0 impostorscore=0 clxscore=1015 phishscore=0 spamscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2202240000 definitions=main-2203220089 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Issuing a memop on a protected vm does not make sense, neither is the memory readable/writable, nor does it make sense to check storage keys. This is why the ioctl will return -EINVAL when it detects the vm to be protected. However, in order to ensure that the vm cannot become protected during the memop, the kvm->lock would need to be taken for the duration of the ioctl. This is also required because kvm_s390_pv_is_protected asserts that the lock must be held. Instead, don't try to prevent this. If user space enables secure execution concurrently with a memop it must accecpt the possibility of the memop failing. Still check if the vm is currently protected, but without locking and consider it a heuristic. Fixes: ef11c9463ae0 ("KVM: s390: Add vm IOCTL for key checked guest absolute memory access") Signed-off-by: Janis Schoetterl-Glausch --- arch/s390/kvm/kvm-s390.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c index ca96f84db2cc..53adbe86a68f 100644 --- a/arch/s390/kvm/kvm-s390.c +++ b/arch/s390/kvm/kvm-s390.c @@ -2385,7 +2385,16 @@ static int kvm_s390_vm_mem_op(struct kvm *kvm, struct kvm_s390_mem_op *mop) return -EINVAL; if (mop->size > MEM_OP_MAX_SIZE) return -E2BIG; - if (kvm_s390_pv_is_protected(kvm)) + /* + * This is technically a heuristic only, if the kvm->lock is not + * taken, it is not guaranteed that the vm is/remains non-protected. + * This is ok from a kernel perspective, wrongdoing is detected + * on the access, -EFAULT is returned and the vm may crash the + * next time it accesses the memory in question. + * There is no sane usecase to do switching and a memop on two + * different CPUs at the same time. + */ + if (kvm_s390_pv_get_handle(kvm)) return -EINVAL; if (mop->flags & KVM_S390_MEMOP_F_SKEY_PROTECTION) { if (access_key_invalid(mop->key)) base-commit: c9b8fecddb5bb4b67e351bbaeaa648a6f7456912 -- 2.32.0