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=-17.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS, 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 F24F9C433B4 for ; Wed, 12 May 2021 22:23:44 +0000 (UTC) Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id B55EC61413 for ; Wed, 12 May 2021 22:23:44 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B55EC61413 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=xen.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from list by lists.xenproject.org with outflank-mailman.126452.238049 (Exim 4.92) (envelope-from ) id 1lgxGJ-0000bv-Rc; Wed, 12 May 2021 22:23:27 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 126452.238049; Wed, 12 May 2021 22:23:27 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1lgxGJ-0000bo-O9; Wed, 12 May 2021 22:23:27 +0000 Received: by outflank-mailman (input) for mailman id 126452; Wed, 12 May 2021 22:23:26 +0000 Received: from mail.xenproject.org ([104.130.215.37]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1lgxGI-0000bi-To for xen-devel@lists.xenproject.org; Wed, 12 May 2021 22:23:26 +0000 Received: from xenbits.xenproject.org ([104.239.192.120]) by mail.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1lgxGH-0004l2-K6; Wed, 12 May 2021 22:23:25 +0000 Received: from [54.239.6.185] (helo=a483e7b01a66.ant.amazon.com) by xenbits.xenproject.org with esmtpsa (TLS1.3:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.92) (envelope-from ) id 1lgxGH-0006mh-EF; Wed, 12 May 2021 22:23:25 +0000 X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=xen.org; s=20200302mail; h=Content-Transfer-Encoding:Content-Type:In-Reply-To: MIME-Version:Date:Message-ID:From:References:Cc:To:Subject; bh=YgBQnV6iBVWQl1Jac0X4gn8+2SozyVSztoo5d0oWYGY=; b=gGmZAku2Z5rMgcH4WZGsorB3fr Ej7wMoaF9xdx07kzZ9v9dYkCyNujdifinwxvtSn8Ot35lofHLGn81T+Q4vlV1PAAjkYSP5e5FPjlQ lu8Hxsvyha3npIz+1SpTR4zzsRr4JVh0GrEJXg+PLYmkKZTpYXj2vqHM1uRn1gWuDkV8=; Subject: Re: [PATCH RFCv2 08/15] xen/arm32: mm: Check if the virtual address is shared before updating it To: Stefano Stabellini Cc: xen-devel@lists.xenproject.org, Wei.Chen@arm.com, Henry.Wang@arm.com, Penny.Zheng@arm.com, Bertrand.Marquis@arm.com, Julien Grall , Volodymyr Babchuk References: <20210425201318.15447-1-julien@xen.org> <20210425201318.15447-9-julien@xen.org> From: Julien Grall Message-ID: Date: Wed, 12 May 2021 23:23:23 +0100 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.10.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-GB Content-Transfer-Encoding: 7bit Hi Stefano, On 12/05/2021 23:00, Stefano Stabellini wrote: > On Sun, 25 Apr 2021, Julien Grall wrote: >> From: Julien Grall >> >> Only the first 2GB of the virtual address space is shared between all >> the page-tables on Arm32. >> >> There is a long outstanding TODO in xen_pt_update() stating that the >> function is can only work with shared mapping. Nobody has ever called > ^ remove > >> the function with private mapping, however as we add more callers >> there is a risk to mess things up. >> >> Introduce a new define to mark the ened of the shared mappings and use > ^end > >> it in xen_pt_update() to verify if the address is correct. >> >> Note that on Arm64, all the mappings are shared. Some compiler may >> complain about an always true check, so the new define is not introduced >> for arm64 and the code is protected with an #ifdef. > > On arm64 we could maybe define SHARED_VIRT_END to an arbitrarely large > value, such as: > > #define SHARED_VIRT_END (1UL<<48) > > or: > > #define SHARED_VIRT_END DIRECTMAP_VIRT_END > > ? I thought about it but I didn't want to define to a random value... I felt not define it was better. > > >> Signed-off-by: Julien Grall >> >> --- >> Changes in v2: >> - New patch >> --- >> xen/arch/arm/mm.c | 11 +++++++++-- >> xen/include/asm-arm/config.h | 4 ++++ >> 2 files changed, 13 insertions(+), 2 deletions(-) >> >> diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c >> index 8fac24d80086..5c17cafff847 100644 >> --- a/xen/arch/arm/mm.c >> +++ b/xen/arch/arm/mm.c >> @@ -1275,11 +1275,18 @@ static int xen_pt_update(unsigned long virt, >> * For arm32, page-tables are different on each CPUs. Yet, they share >> * some common mappings. It is assumed that only common mappings >> * will be modified with this function. >> - * >> - * XXX: Add a check. >> */ >> const mfn_t root = virt_to_mfn(THIS_CPU_PGTABLE); >> >> +#ifdef SHARED_VIRT_END >> + if ( virt > SHARED_VIRT_END || >> + (SHARED_VIRT_END - virt) < nr_mfns ) > > The following would be sufficient, right? > > if ( virt + nr_mfns > SHARED_VIRT_END ) This would not protect against an overflow. So I think it is best if we keep my version. Cheers, -- Julien Grall