From patchwork Fri Jun 23 15:21:59 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alexander Graf X-Patchwork-Id: 9806783 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id CE24060329 for ; Fri, 23 Jun 2017 15:21:51 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id BFC36285E8 for ; Fri, 23 Jun 2017 15:21:51 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id B484E2878F; Fri, 23 Jun 2017 15:21:51 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 7D106285E8 for ; Fri, 23 Jun 2017 15:21:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754441AbdFWPVi (ORCPT ); Fri, 23 Jun 2017 11:21:38 -0400 Received: from mx2.suse.de ([195.135.220.15]:41374 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751999AbdFWPVh (ORCPT ); Fri, 23 Jun 2017 11:21:37 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (charybdis-ext.suse.de [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 4A829AAF2; Fri, 23 Jun 2017 15:21:36 +0000 (UTC) From: Alexander Graf To: kvmarm@lists.cs.columbia.edu Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] KVM: arm/arm64: Handle hva aging while destroying the vm Date: Fri, 23 Jun 2017 17:21:59 +0200 Message-Id: <1498231319-199734-1-git-send-email-agraf@suse.de> X-Mailer: git-send-email 1.8.5.6 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP If we want to age an HVA while the VM is getting destroyed, we have a tiny race window during which we may end up dereferencing an invalid kvm->arch.pgd value. CPU0 CPU1 kvm_age_hva() kvm_mmu_notifier_release() kvm_arch_flush_shadow_all() kvm_free_stage2_pgd() stage2_get_pmd() set kvm->arch.pgd = 0 stage2_get_pud() arch.pgd> This patch adds a check for that case. Signed-off-by: Alexander Graf --- virt/kvm/arm/mmu.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c index f2d5b6c..227931f 100644 --- a/virt/kvm/arm/mmu.c +++ b/virt/kvm/arm/mmu.c @@ -861,6 +861,10 @@ static pud_t *stage2_get_pud(struct kvm *kvm, struct kvm_mmu_memory_cache *cache pgd_t *pgd; pud_t *pud; + /* Do we clash with kvm_free_stage2_pgd()? */ + if (!kvm->arch.pgd) + return NULL; + pgd = kvm->arch.pgd + stage2_pgd_index(addr); if (WARN_ON(stage2_pgd_none(*pgd))) { if (!cache)