From patchwork Fri Nov 16 10:30:36 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Paul Mackerras X-Patchwork-Id: 998826 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=none (mailfrom) smtp.mailfrom=vger.kernel.org (client-ip=209.132.180.67; helo=vger.kernel.org; envelope-from=kvm-ppc-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dmarc=none (p=none dis=none) header.from=ozlabs.org Authentication-Results: ozlabs.org; dkim=pass (2048-bit key; secure) header.d=ozlabs.org header.i=@ozlabs.org header.b="W3m6tyEa"; dkim-atps=neutral Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 42xDyv4Hd9z9sCV for ; Fri, 16 Nov 2018 21:30:47 +1100 (AEDT) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727490AbeKPUma (ORCPT ); Fri, 16 Nov 2018 15:42:30 -0500 Received: from ozlabs.org ([203.11.71.1]:60811 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727454AbeKPUm3 (ORCPT ); Fri, 16 Nov 2018 15:42:29 -0500 Received: by ozlabs.org (Postfix, from userid 1003) id 42xDyq1wLMz9s8F; Fri, 16 Nov 2018 21:30:43 +1100 (AEDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ozlabs.org; s=201707; t=1542364243; bh=XoNS3hp87VxBj6GY6BSba3EbXqxJBffQyUYh6QWhBiI=; h=Date:From:To:Subject:From; b=W3m6tyEayxqFD4c4BOjZi+PFNyc9KOhfm+nT+WYPTWWOgiLOcyrniwRTTqtaQ8UIg JQ7ppIJbXFiuyfYle3EajP9QFduBnCgYmOr6fOqLLv2VLekOh4sMjvl04Xrb1mlQ0E MPEeHphXWl+z4C5pl3AFAm1G7cqnqJqvZkjPrGPAv3/Z6Fu+A3TCStju8+JXV4A91a g9J4SpBpnEIBER4JFyf46VfurCM7JqYH1mqZ5H4IF2+OZq7NTgpYdAum9r+WHkGLwm ZuTCRfyOsfginLiTQ7UO0yrgPYJkkyTW3x3WwxXY4EHb6Z7ME8QslTh8Ni1XGRxigE 3Sd1rTiy435rQ== Date: Fri, 16 Nov 2018 21:30:36 +1100 From: Paul Mackerras To: kvm-ppc@vger.kernel.org, kvm@vger.kernel.org, David Gibson Subject: [PATCH] KVM: PPC: Book3S HV: Fix race between kvm_unmap_hva_range and MMU mode switch Message-ID: <20181116103036.GA19018@blackberry> MIME-Version: 1.0 Content-Disposition: inline User-Agent: Mutt/1.5.24 (2015-08-30) Sender: kvm-ppc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm-ppc@vger.kernel.org Testing has revealed an occasional crash which appears to be caused by a race between kvmppc_switch_mmu_to_hpt and kvm_unmap_hva_range_hv. The symptom is a NULL pointer dereference in __find_linux_pte() called from kvm_unmap_radix() with kvm->arch.pgtable == NULL. Looking at kvmppc_switch_mmu_to_hpt(), it does indeed clear kvm->arch.pgtable (via kvmppc_free_radix()) before setting kvm->arch.radix to NULL, and there is nothing to prevent kvm_unmap_hva_range_hv() or the other MMU callback functions from being called concurrently with kvmppc_switch_mmu_to_hpt() or kvmppc_switch_mmu_to_radix(). This patch therefore adds calls to spin_lock/unlock on the kvm->mmu_lock around the assignments to kvm->arch.radix, and makes sure that the partition-scoped radix tree or HPT is only freed after changing kvm->arch.radix. This also takes the kvm->mmu_lock in kvmppc_rmap_reset() to make sure that the clearing of each rmap array (one per memslot) doesn't happen concurrently with use of the array in the kvm_unmap_hva_range_hv() or the other MMU callbacks. Signed-off-by: Paul Mackerras --- arch/powerpc/kvm/book3s_64_mmu_hv.c | 3 +++ arch/powerpc/kvm/book3s_hv.c | 17 +++++++++++------ 2 files changed, 14 insertions(+), 6 deletions(-) diff --git a/arch/powerpc/kvm/book3s_64_mmu_hv.c b/arch/powerpc/kvm/book3s_64_mmu_hv.c index c615617..a18afda 100644 --- a/arch/powerpc/kvm/book3s_64_mmu_hv.c +++ b/arch/powerpc/kvm/book3s_64_mmu_hv.c @@ -743,12 +743,15 @@ void kvmppc_rmap_reset(struct kvm *kvm) srcu_idx = srcu_read_lock(&kvm->srcu); slots = kvm_memslots(kvm); kvm_for_each_memslot(memslot, slots) { + /* Mutual exclusion with kvm_unmap_hva_range etc. */ + spin_lock(&kvm->mmu_lock); /* * This assumes it is acceptable to lose reference and * change bits across a reset. */ memset(memslot->arch.rmap, 0, memslot->npages * sizeof(*memslot->arch.rmap)); + spin_unlock(&kvm->mmu_lock); } srcu_read_unlock(&kvm->srcu, srcu_idx); } diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c index a56f841..ab43306 100644 --- a/arch/powerpc/kvm/book3s_hv.c +++ b/arch/powerpc/kvm/book3s_hv.c @@ -4532,12 +4532,15 @@ int kvmppc_switch_mmu_to_hpt(struct kvm *kvm) { if (nesting_enabled(kvm)) kvmhv_release_all_nested(kvm); + kvmppc_rmap_reset(kvm); + kvm->arch.process_table = 0; + /* Mutual exclusion with kvm_unmap_hva_range etc. */ + spin_lock(&kvm->mmu_lock); + kvm->arch.radix = 0; + spin_unlock(&kvm->mmu_lock); kvmppc_free_radix(kvm); kvmppc_update_lpcr(kvm, LPCR_VPM1, LPCR_VPM1 | LPCR_UPRT | LPCR_GTSE | LPCR_HR); - kvmppc_rmap_reset(kvm); - kvm->arch.radix = 0; - kvm->arch.process_table = 0; return 0; } @@ -4549,12 +4552,14 @@ int kvmppc_switch_mmu_to_radix(struct kvm *kvm) err = kvmppc_init_vm_radix(kvm); if (err) return err; - + kvmppc_rmap_reset(kvm); + /* Mutual exclusion with kvm_unmap_hva_range etc. */ + spin_lock(&kvm->mmu_lock); + kvm->arch.radix = 1; + spin_unlock(&kvm->mmu_lock); kvmppc_free_hpt(&kvm->arch.hpt); kvmppc_update_lpcr(kvm, LPCR_UPRT | LPCR_GTSE | LPCR_HR, LPCR_VPM1 | LPCR_UPRT | LPCR_GTSE | LPCR_HR); - kvmppc_rmap_reset(kvm); - kvm->arch.radix = 1; return 0; }