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=-5.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 BBC56C48BDF for ; Tue, 15 Jun 2021 19:45:57 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 73DC961166 for ; Tue, 15 Jun 2021 19:45:57 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 73DC961166 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=SwvQFcdZDywF0Na6BlNqeBRcz+Aq4cZ7MB7slUYUBCs=; b=0mMB0A/KJBReDU dh6CBZHap/n2abHRKRGqvqc0AYUMOKhMa+KboXh9Pt3uzEMeKIsGN7Xt5P4HXx0NFiyMSqiHAiDXo psvzmVBXhGp7sX8fC7BtM4B2wN5MHncliRYstTMNykaTTgfpwv8sLQJ/NrGnrOId5OmLtVhe2xh9n BxBhTFXVldK7s93CLMyX1M6SkTQoOA9wva9K4eGDqjlioSK8Zfm6gZhbnhW9QFAsTVZpiUzQAyM37 1UzDiyyBIKzScfXUjTOCFWNnUwy5wiQd7WIUTwDp9Iq02gcxvTDvsSN0GLwPOtOIes3vrI6rO+qvF uCor9u0hDCWNhDTVTwtg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1ltEya-002Xqw-MG; Tue, 15 Jun 2021 19:43:57 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1ltAuH-000w0E-2Z for linux-arm-kernel@lists.infradead.org; Tue, 15 Jun 2021 15:23:15 +0000 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 E7EE9D6E; Tue, 15 Jun 2021 08:23:09 -0700 (PDT) Received: from arm.com (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id B17323F70D; Tue, 15 Jun 2021 08:23:08 -0700 (PDT) Date: Tue, 15 Jun 2021 16:22:06 +0100 From: Dave Martin To: Jeremy Linton Cc: Mark Brown , Catalin Marinas , Will Deacon , linux-arch@vger.kernel.org, Yu-cheng Yu , libc-alpha@sourceware.org, Szabolcs Nagy , linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH v2 0/3] arm64: Enable BTI for the executable as well as the interpreter Message-ID: <20210615152203.GR4187@arm.com> References: <20210604112450.13344-1-broonie@kernel.org> <43e67d7b-aab9-db1f-f74b-a87ba7442d47@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <43e67d7b-aab9-db1f-f74b-a87ba7442d47@arm.com> User-Agent: Mutt/1.5.23 (2014-03-12) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210615_082313_254546_FAF879CF X-CRM114-Status: GOOD ( 27.40 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, Jun 10, 2021 at 11:28:12AM -0500, Jeremy Linton via Libc-alpha wrote: > Hi, > > On 6/4/21 6:24 AM, Mark Brown wrote: > >Deployments of BTI on arm64 have run into issues interacting with > >systemd's MemoryDenyWriteExecute feature. Currently for dynamically > >linked executables the kernel will only handle architecture specific > >properties like BTI for the interpreter, the expectation is that the > >interpreter will then handle any properties on the main executable. > >For BTI this means remapping the executable segments PROT_EXEC | > >PROT_BTI. > > > >This interacts poorly with MemoryDenyWriteExecute since that is > >implemented using a seccomp filter which prevents setting PROT_EXEC on > >already mapped memory and lacks the context to be able to detect that > >memory is already mapped with PROT_EXEC. This series resolves this by > >handling the BTI property for both the interpreter and the main > >executable. > > I've got a Fedora34 system booting in qemu or a model with BTI enabled. On > that system I took the systemd-resolved executable, which is one of the > services with MDWE enabled, and replaced a number of the bti's with nops. I > expect the service to continue to work with the fedora or mainline 5.13 > kernel and it does. If instead I boot with MDWE=no for the service, it > should fail to start given either of those kernels, and it does. > > Thus, I expect that with his patch applied to 5.13 the service will fail to > start regardless of the state of MDWE, but it seems to continue starting > when I set MDWE=yes. Same behavior with v1 FWTW. > > Of course, there is a good chance I've messed something up or i'm missing > something. I should really validate the /lib/ld-linux behavior itself too. I > guess this could just as well be a glibc issue (f34 has glibc 2.33-5 which > appears to have the re-mmap on failure patch). Either way, systemd-resolved > is a LSB PIE, with /lib/ld-linux as its interpreter. I've not dug too deep > into debugging this, cause I've got a couple other things I need to deal > with in the next couple days, and I strongly dislike booting a full > debug+system on the model. chuckle, sorry... [...] If the failure we're trying to detect is that BTI is undesirably left off for the main executable, surely replacing BTIs with NOPs will make no differenece? The behaviour with PROT_BTI clear is strictly more permissive than with PROT_BTI set, so I'm not sure we can test the behaviour this way. Maybe I'm missing sometihng / confused myself somewhere. Looking at /proc//maps after the process starts up may be a more reliable approach, so see what the actual prot value is on the main executable's text pages. Cheers ---Dave _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel