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=-11.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SIGNED_OFF_BY,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 4E5B9C4727F for ; Tue, 29 Sep 2020 08:05:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 18E212075F for ; Tue, 29 Sep 2020 08:05:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727721AbgI2IFC (ORCPT ); Tue, 29 Sep 2020 04:05:02 -0400 Received: from foss.arm.com ([217.140.110.172]:36732 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727709AbgI2IFB (ORCPT ); Tue, 29 Sep 2020 04:05:01 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id F14781063; Tue, 29 Sep 2020 01:05:00 -0700 (PDT) Received: from [10.163.73.175] (unknown [10.163.73.175]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 2601B3F73B; Tue, 29 Sep 2020 01:04:57 -0700 (PDT) Subject: Re: [PATCH] arm64/mm: Validate hotplug range before creating linear mapping To: Will Deacon Cc: linux-arm-kernel@lists.infradead.org, catalin.marinas@arm.com, Mark Rutland , Ard Biesheuvel , Steven Price , Robin Murphy , David Hildenbrand , Andrew Morton , linux-kernel@vger.kernel.org References: <1600332402-30123-1-git-send-email-anshuman.khandual@arm.com> <20200928203539.GA12218@willie-the-truck> From: Anshuman Khandual Message-ID: <09266aed-7eef-5b16-5d52-0dcb7dcb7246@arm.com> Date: Tue, 29 Sep 2020 13:34:24 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20200928203539.GA12218@willie-the-truck> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/29/2020 02:05 AM, Will Deacon wrote: > On Thu, Sep 17, 2020 at 02:16:42PM +0530, Anshuman Khandual wrote: >> During memory hotplug process, the linear mapping should not be created for >> a given memory range if that would fall outside the maximum allowed linear >> range. Else it might cause memory corruption in the kernel virtual space. >> >> Maximum linear mapping region is [PAGE_OFFSET..(PAGE_END -1)] accommodating >> both its ends but excluding PAGE_END. Max physical range that can be mapped >> inside this linear mapping range, must also be derived from its end points. >> >> When CONFIG_ARM64_VA_BITS_52 is enabled, PAGE_OFFSET is computed with the >> assumption of 52 bits virtual address space. However, if the CPU does not >> support 52 bits, then it falls back using 48 bits instead and the PAGE_END >> is updated to reflect this using the vabits_actual. As for PAGE_OFFSET, >> bits [51..48] are ignored by the MMU and remain unchanged, even though the >> effective start address of linear map is now slightly different. Hence, to >> reliably check the physical address range mapped by the linear map, the >> start address should be calculated using vabits_actual. This ensures that >> arch_add_memory() validates memory hot add range for its potential linear >> mapping requirement, before creating it with __create_pgd_mapping(). >> >> Cc: Catalin Marinas >> Cc: Will Deacon >> Cc: Mark Rutland >> Cc: Ard Biesheuvel >> Cc: Steven Price >> Cc: Robin Murphy >> Cc: David Hildenbrand >> Cc: Andrew Morton >> Cc: linux-arm-kernel@lists.infradead.org >> Cc: linux-kernel@vger.kernel.org >> Fixes: 4ab215061554 ("arm64: Add memory hotplug support") >> Signed-off-by: Anshuman Khandual >> --- >> arch/arm64/mm/mmu.c | 27 +++++++++++++++++++++++++++ >> 1 file changed, 27 insertions(+) >> >> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c >> index 75df62fea1b6..d59ffabb9c84 100644 >> --- a/arch/arm64/mm/mmu.c >> +++ b/arch/arm64/mm/mmu.c >> @@ -1433,11 +1433,38 @@ static void __remove_pgd_mapping(pgd_t *pgdir, unsigned long start, u64 size) >> free_empty_tables(start, end, PAGE_OFFSET, PAGE_END); >> } >> >> +static bool inside_linear_region(u64 start, u64 size) >> +{ >> + /* >> + * Linear mapping region is the range [PAGE_OFFSET..(PAGE_END - 1)] >> + * accommodating both its ends but excluding PAGE_END. Max physical >> + * range which can be mapped inside this linear mapping range, must >> + * also be derived from its end points. >> + * >> + * With CONFIG_ARM64_VA_BITS_52 enabled, PAGE_OFFSET is defined with >> + * the assumption of 52 bits virtual address space. However, if the >> + * CPU does not support 52 bits, it falls back using 48 bits and the >> + * PAGE_END is updated to reflect this using the vabits_actual. As >> + * for PAGE_OFFSET, bits [51..48] are ignored by the MMU and remain >> + * unchanged, even though the effective start address of linear map >> + * is now slightly different. Hence, to reliably check the physical >> + * address range mapped by the linear map, the start address should >> + * be calculated using vabits_actual. >> + */ >> + return ((start >= __pa(_PAGE_OFFSET(vabits_actual))) >> + && ((start + size) <= __pa(PAGE_END - 1))); >> +} > > Why isn't this implemented using the existing __is_lm_address()? Not sure, if I understood your suggestion here. The physical address range [start..start + size] needs to be checked against maximum physical range that can be represented inside effective boundaries for the linear mapping i.e [__pa(_PAGE_OFFSET(vabits_actual)..__pa(PAGE_END - 1)]. Are you suggesting [start..start + size] should be first be converted into a virtual address range and then checked against __is_lm_addresses() ? But is not deriving the physical range from from know limits of linear mapping much cleaner ?