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=-10.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham 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 44A66C43387 for ; Mon, 7 Jan 2019 12:41:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 14C5721855 for ; Mon, 7 Jan 2019 12:41:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1546864902; bh=tAbwMxcGkArG8wGT2odcNUqXpcapeF0Vf9JKPKjhACU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=07akRqzda2dgZoWE3J36f2YaoM1rQ19TqoVE2qBbdBF3QFb0lbdZOwHg0F4o7ipmN vu6yZioCW1U5XgaZ56vQxivBAseyAIIUEssNlqC3XBtj7TTiFAXdikBKRh48vq8TW4 NdXugPC3KqcPqvx0cHnR0AWBqlSb0/NkCPJeXx8c= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726827AbfAGMlk (ORCPT ); Mon, 7 Jan 2019 07:41:40 -0500 Received: from mail.kernel.org ([198.145.29.99]:56860 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727277AbfAGMle (ORCPT ); Mon, 7 Jan 2019 07:41:34 -0500 Received: from localhost (5356596B.cm-6-7b.dynamic.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 43DB52183E; Mon, 7 Jan 2019 12:41:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1546864892; bh=tAbwMxcGkArG8wGT2odcNUqXpcapeF0Vf9JKPKjhACU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Vqvx9AIBrqA43/BbQq696+VHS6agx1LR1ZdgUAhzjljkSkleGMM2xV0Q1H5n1/1tN BMam+ygFA5szAShPP5ayMIrXFu09La0jC8RFAfVRKepDf6Tnv9mkjX85min6wG6iAD e20tkH/dP108KhPJzKfFzJm3nAujf/GvYHdPUOqg= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Paul Mackerras Subject: [PATCH 4.20 058/145] KVM: PPC: Book3S HV: Fix race between kvm_unmap_hva_range and MMU mode switch Date: Mon, 7 Jan 2019 13:31:35 +0100 Message-Id: <20190107104444.886183565@linuxfoundation.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190107104437.308206189@linuxfoundation.org> References: <20190107104437.308206189@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review X-Patchwork-Hint: ignore MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 4.20-stable review patch. If anyone has any objections, please let me know. ------------------ From: Paul Mackerras commit 234ff0b729ad882d20f7996591a964965647addf upstream. 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. Fixes: 18c3640cefc7 ("KVM: PPC: Book3S HV: Add infrastructure for running HPT guests on radix host") Cc: stable@vger.kernel.org # v4.15+ Signed-off-by: Paul Mackerras Signed-off-by: Greg Kroah-Hartman --- arch/powerpc/kvm/book3s_64_mmu_hv.c | 3 +++ arch/powerpc/kvm/book3s_hv.c | 17 +++++++++++------ 2 files changed, 14 insertions(+), 6 deletions(-) --- 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); } --- 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 { 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 kv 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; }