From patchwork Tue Feb 25 05:13:01 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kees Cook X-Patchwork-Id: 11402513 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id D0E8614BC for ; Tue, 25 Feb 2020 05:13:47 +0000 (UTC) Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.kernel.org (Postfix) with SMTP id 3881724683 for ; Tue, 25 Feb 2020 05:13:47 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b="LFrOdVRm" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3881724683 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=chromium.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kernel-hardening-return-17900-patchwork-kernel-hardening=patchwork.kernel.org@lists.openwall.com Received: (qmail 7500 invoked by uid 550); 25 Feb 2020 05:13:27 -0000 Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Delivered-To: mailing list kernel-hardening@lists.openwall.com Received: (qmail 7360 invoked from network); 25 Feb 2020 05:13:25 -0000 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=d7eBVkZfRqZ9EInwh3OLHlmLZtMSSsJ/o42DIk8oZMxhnySsiAk/40BJKdER9eY3fe rli4eZ/QnaGBuYBU+IWXNVTB53qA7Vee9Bt/2HA1Km9R+b0nS04PZPg/MUwsDRYIqQ6y lK44GsmoduO1B9VR8gmks6/FyYk+U/Kt/3gElBj03urdU0302+D+36ZzCAuGzrFYGi6U PlYGOOgIFjF/5Zkz9I5jCXlEZ83f/w3q9tGsx8ClE/l8kw1Zr7lPM7Rxr7nKT3aombuT b5L/DzX+Ppt6RPMu7K2m52dsUevXjHGY96KQbaIuyKce8iPb/h28GmVp1XJTYHRq4m/f xglw== X-Gm-Message-State: APjAAAXvwB0paMsMSotgI/SEj8YsND45vVwL52xiByxLuElEOXPWqTAi j9hGYkFEztfvbY65cpEqMhlyWg== 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) 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 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(-)