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=-19.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 C2CF8C64E8A for ; Mon, 30 Nov 2020 13:22:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6C7D8207BC for ; Mon, 30 Nov 2020 13:22:37 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="o1NC+rnv" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725939AbgK3NWV (ORCPT ); Mon, 30 Nov 2020 08:22:21 -0500 Received: from mail.kernel.org ([198.145.29.99]:55260 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725861AbgK3NWV (ORCPT ); Mon, 30 Nov 2020 08:22:21 -0500 Received: from willie-the-truck (236.31.169.217.in-addr.arpa [217.169.31.236]) (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 48334206F9; Mon, 30 Nov 2020 13:21:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1606742500; bh=gp/c1E7Z/fJDz9MSxVD5z46kbUzUAVwzY3qc3WzdfAw=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=o1NC+rnv0ct8v2OvLOXV/3bHWyPXa1peKB6ER4KOtm7UqFOxIhAhpuXKIqRi8NAdb pMM18yWdbu20bY679BQLRr69tRIT6UVJcvY88CM9WJMv+7OOV9XyoGeBE+KcYXYU2j WId7gM2IrW69ZGYIT4hh3nForfeKOmmxKV7nqxWg= Date: Mon, 30 Nov 2020 13:21:33 +0000 From: Will Deacon To: Yanan Wang Cc: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Marc Zyngier , Catalin Marinas , James Morse , Julien Thierry , Suzuki K Poulose , Gavin Shan , Quentin Perret , wanghaibin.wang@huawei.com, yezengruan@huawei.com, zhukeqian1@huawei.com, yuzenghui@huawei.com, jiangkunkun@huawei.com, wangjingyi11@huawei.com, lushenming@huawei.com Subject: Re: [RFC PATCH 1/3] KVM: arm64: Fix possible memory leak in kvm stage2 Message-ID: <20201130132133.GA24837@willie-the-truck> References: <20201130121847.91808-1-wangyanan55@huawei.com> <20201130121847.91808-2-wangyanan55@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201130121847.91808-2-wangyanan55@huawei.com> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Nov 30, 2020 at 08:18:45PM +0800, Yanan Wang wrote: > When installing a new leaf pte onto an invalid ptep, we need to get_page(ptep). > When just updating a valid leaf ptep, we shouldn't get_page(ptep). > Incorrect page_count of translation tables might lead to memory leak, > when unmapping a stage 2 memory range. Did you find this by inspection, or did you hit this in practice? I'd be interested to see the backtrace for mapping over an existing mapping. > Signed-off-by: Yanan Wang > --- > arch/arm64/kvm/hyp/pgtable.c | 7 ++++--- > 1 file changed, 4 insertions(+), 3 deletions(-) > > diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c > index 0271b4a3b9fe..696b6aa83faf 100644 > --- a/arch/arm64/kvm/hyp/pgtable.c > +++ b/arch/arm64/kvm/hyp/pgtable.c > @@ -186,6 +186,7 @@ static bool kvm_set_valid_leaf_pte(kvm_pte_t *ptep, u64 pa, kvm_pte_t attr, > return old == pte; > > smp_store_release(ptep, pte); > + get_page(virt_to_page(ptep)); This is also used for the hypervisor stage-1 page-table, so I'd prefer to leave this function as-is. > return true; > } > > @@ -476,6 +477,7 @@ static bool stage2_map_walker_try_leaf(u64 addr, u64 end, u32 level, > /* There's an existing valid leaf entry, so perform break-before-make */ > kvm_set_invalid_pte(ptep); > kvm_call_hyp(__kvm_tlb_flush_vmid_ipa, data->mmu, addr, level); > + put_page(virt_to_page(ptep)); > kvm_set_valid_leaf_pte(ptep, phys, data->attr, level); > out: > data->phys += granule; Isn't this hunk alone sufficient to solve the problem? Will