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=-10.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 AEAD2C43467 for ; Thu, 8 Oct 2020 10:14:00 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (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 E8A8E2145D for ; Thu, 8 Oct 2020 10:13:59 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E8A8E2145D Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from bilbo.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 4C6Rr46NF2zDqWb for ; Thu, 8 Oct 2020 21:13:56 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=kernel.org (client-ip=198.145.29.99; helo=mail.kernel.org; envelope-from=cmarinas@kernel.org; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=fail (p=none dis=none) header.from=arm.com Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4C6RpC3J8XzDqBc for ; Thu, 8 Oct 2020 21:12:19 +1100 (AEDT) Received: from gaia (unknown [95.149.105.49]) (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 AE8312145D; Thu, 8 Oct 2020 10:12:12 +0000 (UTC) Date: Thu, 8 Oct 2020 11:12:10 +0100 From: Catalin Marinas To: Jann Horn Subject: Re: [PATCH 1/2] mm/mprotect: Call arch_validate_prot under mmap_lock and with length Message-ID: <20201008101209.GD7661@gaia> References: <20201007073932.865218-1-jannh@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201007073932.865218-1-jannh@google.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, Christoph Hellwig , linux-mm@kvack.org, Khalid Aziz , Paul Mackerras , sparclinux@vger.kernel.org, Anthony Yznaga , Andrew Morton , Will Deacon , "David S. Miller" , linux-arm-kernel@lists.infradead.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Wed, Oct 07, 2020 at 09:39:31AM +0200, Jann Horn wrote: > arch_validate_prot() is a hook that can validate whether a given set of > protection flags is valid in an mprotect() operation. It is given the set > of protection flags and the address being modified. > > However, the address being modified can currently not actually be used in > a meaningful way because: > > 1. Only the address is given, but not the length, and the operation can > span multiple VMAs. Therefore, the callee can't actually tell which > virtual address range, or which VMAs, are being targeted. > 2. The mmap_lock is not held, meaning that if the callee were to check > the VMA at @addr, that VMA would be unrelated to the one the > operation is performed on. > > Currently, custom arch_validate_prot() handlers are defined by > arm64, powerpc and sparc. > arm64 and powerpc don't care about the address range, they just check the > flags against CPU support masks. > sparc's arch_validate_prot() attempts to look at the VMA, but doesn't take > the mmap_lock. > > Change the function signature to also take a length, and move the > arch_validate_prot() call in mm/mprotect.c down into the locked region. For arm64 mte, I noticed the arch_validate_prot() issue with multiple vmas and addressed this in a different way: https://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git/commit/?h=for-next/mte&id=c462ac288f2c97e0c1d9ff6a65955317e799f958 https://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git/commit/?h=for-next/mte&id=0042090548740921951f31fc0c20dcdb96638cb0 Both patches queued for 5.10. Basically, arch_calc_vm_prot_bits() returns a VM_MTE if PROT_MTE has been requested. The newly introduced arch_validate_flags() will check the VM_MTE flag against what the system supports and this covers both mmap() and mprotect(). Note that arch_validate_prot() only handles the latter and I don't think it's sufficient for SPARC ADI. For arm64 MTE we definitely wanted mmap() flags to be validated. In addition, there's a new arch_calc_vm_flag_bits() which allows us to set a VM_MTE_ALLOWED on a vma if the conditions are right (MAP_ANONYMOUS or shmem_mmap(): https://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git/commit/?h=for-next/mte&id=b3fbbea4c00220f62e6f7e2514466e6ee81f7f60 -- Catalin