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=-3.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 1EC11C35DF2 for ; Tue, 25 Feb 2020 05:13:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DC2B924682 for ; Tue, 25 Feb 2020 05:13:15 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b="LFrOdVRm" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726400AbgBYFNO (ORCPT ); Tue, 25 Feb 2020 00:13:14 -0500 Received: from mail-pl1-f195.google.com ([209.85.214.195]:43886 "EHLO mail-pl1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725788AbgBYFNO (ORCPT ); Tue, 25 Feb 2020 00:13:14 -0500 Received: by mail-pl1-f195.google.com with SMTP id p11so4987220plq.10 for ; Mon, 24 Feb 2020 21:13:14 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=CQB4rWAgQlshK2jar7JtwK95ipRQeMQdrfjF9c60b3Q=; b=LFrOdVRmnVadjqGd8oJrAQjMoolYjWN9vYwc3EwXw87IXTST26Jz+ZUqqf3Cwz9CoS 8nvpcKutc2DDmK9larltPBH0crdkmid8hDBB1a3PpJF4ipvEpIkrP1nwnZd6QtbZKUqw THv95WvZqUUgZ2hYd5vk1iRfZrXdVhQeyUBzQ= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=CQB4rWAgQlshK2jar7JtwK95ipRQeMQdrfjF9c60b3Q=; b=jecIb7LFddsCed11T4Tp3HXW5sQT9C/QtswUBnkOwJHb65cWnIg8t5K2MlrjFBqx5f 6K/Hkt4H1d6f7lFkAvaIDQdykJW2CqSUVT6V0XFraA0bHjJKU6h0ozmDQPI4bTunqqcg XrnHa7aPPCHOHqZTLd4k2qt/ZqLi+CcJnkOOAN8wdMm9hM7fxi+bUw5ujBKmelSIZypR XLZRou8oKa40vlSpxyTjOmBlDVUbpEAm/tzJCVVeLmwobAhmlIls1TOkYdGAVkuhqMin 2rnAnTn8cTeX+kk3cnFnE3l7qOAAM+CLBmce65dlahIkAJ01ABfTWfSgVhNiqnEP2jF0 dcpg== X-Gm-Message-State: APjAAAXgHwkYTR60b4EsXFA/H9DilNDRWy5ubTBqBxECRd5fx4cyIo6O jULEO2hqZup9JmLivZSRHZ1iag== X-Google-Smtp-Source: APXvYqyEp2DduArcsAfDzCxBtvCjTHJyL0Kka4MDfFR/IyZ8Q21kRRLDuvjt0qN6ORbpfkkeenKrsA== X-Received: by 2002:a17:90a:da03:: with SMTP id e3mr3139897pjv.57.1582607592644; Mon, 24 Feb 2020 21:13:12 -0800 (PST) Received: from www.outflux.net (smtp.outflux.net. [198.145.64.163]) by smtp.gmail.com with ESMTPSA id h13sm1274471pjc.9.2020.02.24.21.13.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 24 Feb 2020 21:13:11 -0800 (PST) From: Kees Cook To: Borislav Petkov Cc: Kees Cook , Hector Marco-Gisbert , Jason Gunthorpe , Catalin Marinas , Russell King , Will Deacon , Jann Horn , x86@kernel.org, linux-arm-kernel@lists.infradead.org, kernel-hardening@lists.openwall.com, linux-kernel@vger.kernel.org Subject: [PATCH v4 0/6] binfmt_elf: Update READ_IMPLIES_EXEC logic for modern CPUs Date: Mon, 24 Feb 2020 21:13:01 -0800 Message-Id: <20200225051307.6401-1-keescook@chromium.org> X-Mailer: git-send-email 2.20.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, This is a refresh of my earlier attempt to fix READ_IMPLIES_EXEC. I think it incorporates the feedback from v2 (there are no code changes between v3 and v4; I've just added Reviews/Acks and directed at Boris, as it seems Ingo is busy). The selftest from v3 has been remove from v4, as I will land it separately via Shuah's selftest tree. This series is for x86, arm, and arm64; I'd like it to go via -tip, though, just to keep this change together with the selftest. To that end, I'd like to collect Acks from the respective architecture maintainers. (Note that most other architectures don't suffer from this problem. e.g. powerpc's behavior appears to already be correct. MIPS may need adjusting but the history of CPU features and toolchain behavior is very unclear to me.) Repeating the commit log from later in the series: The READ_IMPLIES_EXEC work-around was designed for old toolchains that lacked the ELF PT_GNU_STACK marking under the assumption that toolchains that couldn't specify executable permission flags for the stack may not know how to do it correctly for any memory region. This logic is sensible for having ancient binaries coexist in a system with possibly NX memory, but was implemented in a way that equated having a PT_GNU_STACK marked executable as being as "broken" as lacking the PT_GNU_STACK marking entirely. Things like unmarked assembly and stack trampolines may cause PT_GNU_STACK to need an executable bit, but they do not imply all mappings must be executable. This confusion has led to situations where modern programs with explicitly marked executable stack are forced into the READ_IMPLIES_EXEC state when no such thing is needed. (And leads to unexpected failures when mmap()ing regions of device driver memory that wish to disallow VM_EXEC[1].) In looking for other reasons for the READ_IMPLIES_EXEC behavior, Jann Horn noted that glibc thread stacks have always been marked RWX (until 2003 when they started tracking the PT_GNU_STACK flag instead[2]). And musl doesn't support executable stacks at all[3]. As such, no breakage for multithreaded applications is expected from this change. [1] https://lkml.kernel.org/r/20190418055759.GA3155@mellanox.com [2] https://sourceware.org/git/?p=glibc.git;a=commitdiff;h=54ee14b3882 [3] https://lkml.kernel.org/r/20190423192534.GN23599@brightrain.aerifal.cx -Kees v4: - split selftest into separate series to go via Shuah's tree - add Reviews/Acks v3: https://lore.kernel.org/lkml/20200210193049.64362-1-keescook@chromium.org v2: https://lore.kernel.org/lkml/20190424203408.GA11386@beast/ v1: https://lore.kernel.org/lkml/20190423181210.GA2443@beast/ Kees Cook (6): x86/elf: Add table to document READ_IMPLIES_EXEC x86/elf: Split READ_IMPLIES_EXEC from executable GNU_STACK x86/elf: Disable automatic READ_IMPLIES_EXEC for 64-bit address spaces arm32/64, elf: Add tables to document READ_IMPLIES_EXEC arm32/64, elf: Split READ_IMPLIES_EXEC from executable GNU_STACK arm64, elf: Disable automatic READ_IMPLIES_EXEC for 64-bit address spaces arch/arm/kernel/elf.c | 27 +++++++++++++++++++++++---- arch/arm64/include/asm/elf.h | 23 ++++++++++++++++++++++- arch/x86/include/asm/elf.h | 22 +++++++++++++++++++++- fs/compat_binfmt_elf.c | 5 +++++ 4 files changed, 71 insertions(+), 6 deletions(-) -- 2.20.1 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=-3.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_GIT 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 E791AC35DF5 for ; 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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id h13sm1274471pjc.9.2020.02.24.21.13.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 24 Feb 2020 21:13:11 -0800 (PST) From: Kees Cook To: Borislav Petkov Subject: [PATCH v4 0/6] binfmt_elf: Update READ_IMPLIES_EXEC logic for modern CPUs Date: Mon, 24 Feb 2020 21:13:01 -0800 Message-Id: <20200225051307.6401-1-keescook@chromium.org> X-Mailer: git-send-email 2.20.1 MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200224_211314_690437_9BDC01AF X-CRM114-Status: GOOD ( 12.56 ) 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: Kees Cook , Jann Horn , Catalin Marinas , x86@kernel.org, Hector Marco-Gisbert , Russell King , linux-kernel@vger.kernel.org, Jason Gunthorpe , kernel-hardening@lists.openwall.com, Will Deacon , linux-arm-kernel@lists.infradead.org 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 Hi, This is a refresh of my earlier attempt to fix READ_IMPLIES_EXEC. I think it incorporates the feedback from v2 (there are no code changes between v3 and v4; I've just added Reviews/Acks and directed at Boris, as it seems Ingo is busy). The selftest from v3 has been remove from v4, as I will land it separately via Shuah's selftest tree. This series is for x86, arm, and arm64; I'd like it to go via -tip, though, just to keep this change together with the selftest. To that end, I'd like to collect Acks from the respective architecture maintainers. (Note that most other architectures don't suffer from this problem. e.g. powerpc's behavior appears to already be correct. MIPS may need adjusting but the history of CPU features and toolchain behavior is very unclear to me.) Repeating the commit log from later in the series: The READ_IMPLIES_EXEC work-around was designed for old toolchains that lacked the ELF PT_GNU_STACK marking under the assumption that toolchains that couldn't specify executable permission flags for the stack may not know how to do it correctly for any memory region. This logic is sensible for having ancient binaries coexist in a system with possibly NX memory, but was implemented in a way that equated having a PT_GNU_STACK marked executable as being as "broken" as lacking the PT_GNU_STACK marking entirely. Things like unmarked assembly and stack trampolines may cause PT_GNU_STACK to need an executable bit, but they do not imply all mappings must be executable. This confusion has led to situations where modern programs with explicitly marked executable stack are forced into the READ_IMPLIES_EXEC state when no such thing is needed. (And leads to unexpected failures when mmap()ing regions of device driver memory that wish to disallow VM_EXEC[1].) In looking for other reasons for the READ_IMPLIES_EXEC behavior, Jann Horn noted that glibc thread stacks have always been marked RWX (until 2003 when they started tracking the PT_GNU_STACK flag instead[2]). And musl doesn't support executable stacks at all[3]. As such, no breakage for multithreaded applications is expected from this change. [1] https://lkml.kernel.org/r/20190418055759.GA3155@mellanox.com [2] https://sourceware.org/git/?p=glibc.git;a=commitdiff;h=54ee14b3882 [3] https://lkml.kernel.org/r/20190423192534.GN23599@brightrain.aerifal.cx -Kees v4: - split selftest into separate series to go via Shuah's tree - add Reviews/Acks v3: https://lore.kernel.org/lkml/20200210193049.64362-1-keescook@chromium.org v2: https://lore.kernel.org/lkml/20190424203408.GA11386@beast/ v1: https://lore.kernel.org/lkml/20190423181210.GA2443@beast/ Kees Cook (6): x86/elf: Add table to document READ_IMPLIES_EXEC x86/elf: Split READ_IMPLIES_EXEC from executable GNU_STACK x86/elf: Disable automatic READ_IMPLIES_EXEC for 64-bit address spaces arm32/64, elf: Add tables to document READ_IMPLIES_EXEC arm32/64, elf: Split READ_IMPLIES_EXEC from executable GNU_STACK arm64, elf: Disable automatic READ_IMPLIES_EXEC for 64-bit address spaces arch/arm/kernel/elf.c | 27 +++++++++++++++++++++++---- arch/arm64/include/asm/elf.h | 23 ++++++++++++++++++++++- arch/x86/include/asm/elf.h | 22 +++++++++++++++++++++- fs/compat_binfmt_elf.c | 5 +++++ 4 files changed, 71 insertions(+), 6 deletions(-) -- 2.20.1 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel