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=-8.2 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_MUTT 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 36259C31E45 for ; Thu, 13 Jun 2019 11:18:53 +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 02B2E20B7C for ; Thu, 13 Jun 2019 11:18:53 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="kRd/NURZ" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 02B2E20B7C Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-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.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject: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=WoeTd4lNMX2r5S6lcxxWZoh32WxSLc3+M7LOcUpbN1M=; b=kRd/NURZ6x+nS9 3rtYtMyOL+BhqNvDl1DoVq+FTA8cJ0aRG3bxAj7+sL7oz9sXsVKljKXmJ9uqG18Rxv+hxhpt60Sbj I0twB3jPbkdrI0Upr9mB/8Gpb0Kt4Z0Fpd8PWgchDctT+zRogogiBmzjz8Rx0fckjXqUeTV0d1I4O PSQY/0ZsaSVqKEZgXlypsOjaO0HKnJ4oLI9utKvLPJMzwEY10YYBlP8irT1PjSzeyESWxJsdZWvih AHYbzx/bJqCenI3EuqvCUzQ/gkiE37X6lUPXQ4gnaD/uhWl23yIi3ezpO9hKX6cJmOjet1QvmRoyU M8mjN+DcYRvEskfC8YbA==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1hbNkp-000559-2o; Thu, 13 Jun 2019 11:18:51 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1hbNj9-0003Hb-Bw for linux-arm-kernel@lists.infradead.org; Thu, 13 Jun 2019 11:17:09 +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 68C33367; Thu, 13 Jun 2019 04:17:06 -0700 (PDT) Received: from e103592.cambridge.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 11EDF3F694; Thu, 13 Jun 2019 04:18:44 -0700 (PDT) Date: Thu, 13 Jun 2019 12:16:59 +0100 From: Dave Martin To: Andrey Konovalov Subject: Re: [PATCH v17 03/15] arm64: Introduce prctl() options to control the tagged user addresses ABI Message-ID: <20190613111659.GX28398@e103592.cambridge.arm.com> References: MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: 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-20190613_041707_532568_427FFAF6 X-CRM114-Status: GOOD ( 25.11 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , kvm@vger.kernel.org, Christian Koenig , Szabolcs Nagy , Catalin Marinas , Will Deacon , dri-devel@lists.freedesktop.org, Kostya Serebryany , Khalid Aziz , Lee Smith , linux-kselftest@vger.kernel.org, Vincenzo Frascino , Jacob Bramley , Leon Romanovsky , linux-rdma@vger.kernel.org, amd-gfx@lists.freedesktop.org, Christoph Hellwig , Jason Gunthorpe , Dmitry Vyukov , Evgeniy Stepanov , linux-media@vger.kernel.org, Kees Cook , Ruben Ayrapetyan , Kevin Brodsky , Alex Williamson , Mauro Carvalho Chehab , linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, Greg Kroah-Hartman , Felix Kuehling , linux-kernel@vger.kernel.org, Jens Wiklander , Ramana Radhakrishnan , Alexander Deucher , Andrew Morton , enh , Robin Murphy , Yishai Hadas , Luc Van Oostenryck Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, Jun 12, 2019 at 01:43:20PM +0200, Andrey Konovalov wrote: > From: Catalin Marinas > > It is not desirable to relax the ABI to allow tagged user addresses into > the kernel indiscriminately. This patch introduces a prctl() interface > for enabling or disabling the tagged ABI with a global sysctl control > for preventing applications from enabling the relaxed ABI (meant for > testing user-space prctl() return error checking without reconfiguring > the kernel). The ABI properties are inherited by threads of the same > application and fork()'ed children but cleared on execve(). > > The PR_SET_TAGGED_ADDR_CTRL will be expanded in the future to handle > MTE-specific settings like imprecise vs precise exceptions. > > Signed-off-by: Catalin Marinas > --- > arch/arm64/include/asm/processor.h | 6 +++ > arch/arm64/include/asm/thread_info.h | 1 + > arch/arm64/include/asm/uaccess.h | 3 +- > arch/arm64/kernel/process.c | 67 ++++++++++++++++++++++++++++ > include/uapi/linux/prctl.h | 5 +++ > kernel/sys.c | 16 +++++++ > 6 files changed, 97 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h > index fcd0e691b1ea..fee457456aa8 100644 > --- a/arch/arm64/include/asm/processor.h > +++ b/arch/arm64/include/asm/processor.h > @@ -307,6 +307,12 @@ extern void __init minsigstksz_setup(void); > /* PR_PAC_RESET_KEYS prctl */ > #define PAC_RESET_KEYS(tsk, arg) ptrauth_prctl_reset_keys(tsk, arg) > > +/* PR_TAGGED_ADDR prctl */ (A couple of comments I missed in my last reply:) Name mismatch? > +long set_tagged_addr_ctrl(unsigned long arg); > +long get_tagged_addr_ctrl(void); > +#define SET_TAGGED_ADDR_CTRL(arg) set_tagged_addr_ctrl(arg) > +#define GET_TAGGED_ADDR_CTRL() get_tagged_addr_ctrl() > + [...] > diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c > index 3767fb21a5b8..69d0be1fc708 100644 > --- a/arch/arm64/kernel/process.c > +++ b/arch/arm64/kernel/process.c > @@ -30,6 +30,7 @@ > #include > #include > #include > +#include > #include > #include > #include > @@ -323,6 +324,7 @@ void flush_thread(void) > fpsimd_flush_thread(); > tls_thread_flush(); > flush_ptrace_hw_breakpoint(current); > + clear_thread_flag(TIF_TAGGED_ADDR); > } > > void release_thread(struct task_struct *dead_task) > @@ -552,3 +554,68 @@ void arch_setup_new_exec(void) > > ptrauth_thread_init_user(current); > } > + > +/* > + * Control the relaxed ABI allowing tagged user addresses into the kernel. > + */ > +static unsigned int tagged_addr_prctl_allowed = 1; > + > +long set_tagged_addr_ctrl(unsigned long arg) > +{ > + if (!tagged_addr_prctl_allowed) > + return -EINVAL; So, tagging can actually be locked on by having a process enable it and then some possibly unrelated process clearing tagged_addr_prctl_allowed. That feels a bit weird. Do we want to allow a process that has tagging on to be able to turn it off at all? Possibly things like CRIU might want to do that. > + if (is_compat_task()) > + return -EINVAL; > + if (arg & ~PR_TAGGED_ADDR_ENABLE) > + return -EINVAL; How do we expect this argument to be extended in the future? I'm wondering whether this is really a bitmask or an enum, or a mixture of the two. Maybe it doesn't matter. > + > + if (arg & PR_TAGGED_ADDR_ENABLE) > + set_thread_flag(TIF_TAGGED_ADDR); > + else > + clear_thread_flag(TIF_TAGGED_ADDR); I think update_thread_flag() could be used here. [...] Cheers ---Dave _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel