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=-19.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,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 A94DDC43461 for ; Thu, 20 May 2021 10:43:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7D98761028 for ; Thu, 20 May 2021 10:43:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237972AbhETKoL (ORCPT ); Thu, 20 May 2021 06:44:11 -0400 Received: from mail.kernel.org ([198.145.29.99]:55508 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236659AbhETK3A (ORCPT ); Thu, 20 May 2021 06:29:00 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 17F0261C2E; Thu, 20 May 2021 09:51:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1621504270; bh=ONUvG69htUK3IfTeZ8iBDJdzdN4TErSqN6rWACDy5b8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=qO8sGchtj0UDLxcraSwL91ZiGXzt42Q6e44QNLJUFwJB66nyC9OQbjrWyUDsi1mzG 9XUtrnh0wjbs8qJSKIjOZtbCXrw/d6u/fdmtms4Ah+EhEN33vHXGynqMfnMOzXHHnv B+qIk+UaXjVrIdilRmiowpRKl5ZlurzvEYl7W2zg= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Heiko Carstens , Christian Borntraeger , David Hildenbrand , Janosch Frank , Cornelia Huck Subject: [PATCH 4.14 135/323] KVM: s390: fix guarded storage control register handling Date: Thu, 20 May 2021 11:20:27 +0200 Message-Id: <20210520092124.743840407@linuxfoundation.org> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210520092120.115153432@linuxfoundation.org> References: <20210520092120.115153432@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Heiko Carstens commit 44bada28219031f9e8e86b84460606efa57b871e upstream. store_regs_fmt2() has an ordering problem: first the guarded storage facility is enabled on the local cpu, then preemption disabled, and then the STGSC (store guarded storage controls) instruction is executed. If the process gets scheduled away between enabling the guarded storage facility and before preemption is disabled, this might lead to a special operation exception and therefore kernel crash as soon as the process is scheduled back and the STGSC instruction is executed. Fixes: 4e0b1ab72b8a ("KVM: s390: gs support for kvm guests") Signed-off-by: Heiko Carstens Reviewed-by: Christian Borntraeger Reviewed-by: David Hildenbrand Reviewed-by: Janosch Frank Reviewed-by: Cornelia Huck Cc: # 4.12 Link: https://lore.kernel.org/r/20210415080127.1061275-1-hca@linux.ibm.com Signed-off-by: Christian Borntraeger Signed-off-by: Greg Kroah-Hartman --- arch/s390/kvm/kvm-s390.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/arch/s390/kvm/kvm-s390.c +++ b/arch/s390/kvm/kvm-s390.c @@ -3395,16 +3395,16 @@ static void store_regs(struct kvm_vcpu * current->thread.fpu.fpc = vcpu->arch.host_fpregs.fpc; current->thread.fpu.regs = vcpu->arch.host_fpregs.regs; if (MACHINE_HAS_GS) { + preempt_disable(); __ctl_set_bit(2, 4); if (vcpu->arch.gs_enabled) save_gs_cb(current->thread.gs_cb); - preempt_disable(); current->thread.gs_cb = vcpu->arch.host_gscb; restore_gs_cb(vcpu->arch.host_gscb); - preempt_enable(); if (!vcpu->arch.host_gscb) __ctl_clear_bit(2, 4); vcpu->arch.host_gscb = NULL; + preempt_enable(); } }