From patchwork Fri Mar 27 06:48:14 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kees Cook X-Patchwork-Id: 11461767 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 E05ED1668 for ; Fri, 27 Mar 2020 06:48:59 +0000 (UTC) Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.kernel.org (Postfix) with SMTP id 48DA720717 for ; Fri, 27 Mar 2020 06:48:59 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b="I5pLNO+f" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 48DA720717 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-18250-patchwork-kernel-hardening=patchwork.kernel.org@lists.openwall.com Received: (qmail 26312 invoked by uid 550); 27 Mar 2020 06:48:39 -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 26157 invoked from network); 27 Mar 2020 06:48:38 -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=e2pldkrhAni9nq8EyiG2WO78f/APBgebCGeZjhrmshQ=; b=I5pLNO+fPogPHiacztpG1HxVvtnTLCdqXJT+PYXFAYy2wxLIwXNdmFqAS1I1f0M/jk i7aiI8cdZcbouxeLQbQqZcLjULDiMw3oqCK7zfUVhtO0VEAHkOFMQ2tOJkveDwz0wuv6 pOsphc56mqYDnuZStj5ScZg0AFgtI8LBlfI3I= 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=e2pldkrhAni9nq8EyiG2WO78f/APBgebCGeZjhrmshQ=; b=GxeKuVKqHysqGKcDrDKsthJWzam7HR5m8pbaRrXYCymAgnDn8W3Za/jGWkUm/V8X5o qcLCy+uOAFbYwe5xN4DF/1QM0SgMH9CMdL8eAoCzGCHPdeDhoVICgOAF/Z5lVS4r4Ptd XhkfqD1E+Z4+v1HweajoEwO80QCcc2COPWBCcwfwCdnbh49/NaOXnbNSEklg8Ek1pCoW qnW2HGeX3A1Ru9UOG/eN0xG+TXaek6XE7/VFS+4IlUbbX3Y2eYYkb07I3X9SeKup6TZT kPlYxXuufdJ8I/ppFG79LG0sXYlHnNZvknCX8hZSaqGXOu3frPUmA4P5JO70jLQLLKQv Wyvw== X-Gm-Message-State: ANhLgQ0GGljeg/yVY9oWvhzxuKIXRzCqcawcna1mCuPd+pWKwzSa4NdP tWLPkscS+QlgwjD1HQpvfuuieQ== X-Google-Smtp-Source: ADFU+vu33/tER7UbAE9saaXS5jjv8U5NDlXNrJgfePpmE/SLJRv4FbdKQSggX0D5kcr6Hk9V6uB9jw== X-Received: by 2002:a17:90a:bf18:: with SMTP id c24mr4158631pjs.125.1585291706174; Thu, 26 Mar 2020 23:48:26 -0700 (PDT) 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 v5 0/6] binfmt_elf: Update READ_IMPLIES_EXEC logic for modern CPUs Date: Thu, 26 Mar 2020 23:48:14 -0700 Message-Id: <20200327064820.12602-1-keescook@chromium.org> X-Mailer: git-send-email 2.20.1 MIME-Version: 1.0 Hi, This continues my attempt to fix READ_IMPLIES_EXEC. :) This series is for x86, arm, and arm64; I'd like it to go via -tip, though, just to keep these changes together, as they're related. (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 Thanks! -Kees v5: - re-align tables and use full name of PT_GNU_STACK (bp) v4: https://lore.kernel.org/lkml/20200225051307.6401-1-keescook@chromium.org 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 PT_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 PT_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(-)