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=-9.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham 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 73E72C35254 for ; Mon, 10 Feb 2020 19:31:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 413F920838 for ; Mon, 10 Feb 2020 19:31:13 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b="PoL0XhCM" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727828AbgBJTbM (ORCPT ); Mon, 10 Feb 2020 14:31:12 -0500 Received: from mail-oi1-f193.google.com ([209.85.167.193]:47031 "EHLO mail-oi1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727641AbgBJTbF (ORCPT ); Mon, 10 Feb 2020 14:31:05 -0500 Received: by mail-oi1-f193.google.com with SMTP id a22so10291165oid.13 for ; Mon, 10 Feb 2020 11:31:04 -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:in-reply-to:references :mime-version:content-transfer-encoding; bh=vV+4L9n935hAwwy1rny/bKPJmpM6IQkGJafPemnuM6M=; b=PoL0XhCMF5RYylDc0l4IgFMeB8xwO+uVffzPYfytDnFxlYeMxyX/mZuQokiRqvLpeB 3BSmLKsw8Mn0fTOGDf5FiPjNmXvq0HmdnXXBN/WXOAJCOAtbktliwg0Ij4BFjNLNEwz1 LFDL39Nbv292S1gxIrW8F3TJd9vj+dby5RYxI= 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:in-reply-to :references:mime-version:content-transfer-encoding; bh=vV+4L9n935hAwwy1rny/bKPJmpM6IQkGJafPemnuM6M=; b=YGCvyxBG0TaDQJyVO0Xm38DHTqMZqZ5PqGIpiu2sUYuJhrW+7xV5NNG7OC8ZvuPCry 77GV7g/uVXJxp2LsXiKkGp1d628qNxczDpwa9scz/2N0NVA52oPUISTaSgdWL1D5r7Pk 0F7K7wL39f1Q6HVrC2VG9j490bVVz+ub53edAGp/Qve3RtrffgvZSvo3tsrk50FJVDc8 HuhJheP0cpiHNW37hRA/oMuorTnbkaiikeziDUZm2xM2SLQHdFMwoFJ0ofzEP4wVKSN6 wNpHKkdo69zDnuV5fpkQISPzLiunVuaytcHuugugP0bLqZ8JAxkI7UFUAwr/hR4BIRtw /nGg== X-Gm-Message-State: APjAAAW8K0Eh2vV8iRI/dWTHeE4rEjDIrGGUjzvPl/ikghS8ZtAFAkjl Jwpg4rlteDVxL1J5BKCczLNPmw== X-Google-Smtp-Source: APXvYqxxYA/0/Zbqi4Hv0JHtPdrzzbONYFkwCVp0/iu2hk9k8CQImN2sdfiTosdmQZKPTHVPQ7l30Q== X-Received: by 2002:aca:5083:: with SMTP id e125mr424241oib.96.1581363063722; Mon, 10 Feb 2020 11:31:03 -0800 (PST) Received: from www.outflux.net (smtp.outflux.net. [198.145.64.163]) by smtp.gmail.com with ESMTPSA id f1sm370846otq.4.2020.02.10.11.31.00 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 10 Feb 2020 11:31:02 -0800 (PST) From: Kees Cook To: Ingo Molnar Cc: Kees Cook , Hector Marco-Gisbert , Catalin Marinas , Will Deacon , Jason Gunthorpe , Jann Horn , Russell King , x86@kernel.org, kernel-hardening@lists.openwall.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: [PATCH v3 5/7] arm32/64, elf: Split READ_IMPLIES_EXEC from executable GNU_STACK Date: Mon, 10 Feb 2020 11:30:47 -0800 Message-Id: <20200210193049.64362-6-keescook@chromium.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200210193049.64362-1-keescook@chromium.org> References: <20200210193049.64362-1-keescook@chromium.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. This changes arm32 and arm64 compat together, to keep behavior the same. [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 Suggested-by: Hector Marco-Gisbert Signed-off-by: Kees Cook --- arch/arm/kernel/elf.c | 5 +++-- arch/arm64/include/asm/elf.h | 5 +++-- 2 files changed, 6 insertions(+), 4 deletions(-) diff --git a/arch/arm/kernel/elf.c b/arch/arm/kernel/elf.c index 2f69cf978fe3..6965a673a141 100644 --- a/arch/arm/kernel/elf.c +++ b/arch/arm/kernel/elf.c @@ -87,12 +87,13 @@ EXPORT_SYMBOL(elf_set_personality); * ELF:              |            |           | * -------------------------------|------------| * missing GNU_STACK | exec-all   | exec-all  | - * GNU_STACK == RWX  | exec-all   | exec-all  | + * GNU_STACK == RWX  | exec-all   | exec-stack | * GNU_STACK == RW   | exec-all  | exec-none | * * exec-all : all PROT_READ user mappings are executable, except when * backed by files on a noexec-filesystem. * exec-none : only PROT_EXEC user mappings are executable. + * exec-stack: only the stack and PROT_EXEC user mappings are executable. * * *this column has no architectural effect: NX markings are ignored by * hardware, but may have behavioral effects when "wants X" collides with @@ -102,7 +103,7 @@ EXPORT_SYMBOL(elf_set_personality); */ int arm_elf_read_implies_exec(int executable_stack) { - if (executable_stack != EXSTACK_DISABLE_X) + if (executable_stack == EXSTACK_DEFAULT) return 1; if (cpu_architecture() < CPU_ARCH_ARMv6) return 1; diff --git a/arch/arm64/include/asm/elf.h b/arch/arm64/include/asm/elf.h index 7fc779e3f1ec..03ada29984a7 100644 --- a/arch/arm64/include/asm/elf.h +++ b/arch/arm64/include/asm/elf.h @@ -106,17 +106,18 @@ * ELF:              |            |            | * -------------------------------|------------| * missing GNU_STACK | exec-all   | exec-all   | - * GNU_STACK == RWX  | exec-all   | exec-all   | + * GNU_STACK == RWX  | exec-stack | exec-stack | * GNU_STACK == RW   | exec-none | exec-none | * * exec-all : all PROT_READ user mappings are executable, except when * backed by files on a noexec-filesystem. * exec-none : only PROT_EXEC user mappings are executable. + * exec-stack: only the stack and PROT_EXEC user mappings are executable. * * *all arm64 CPUs support NX, so there is no "lacks NX" column. * */ -#define elf_read_implies_exec(ex,stk) (stk != EXSTACK_DISABLE_X) +#define elf_read_implies_exec(ex,stk) (stk == EXSTACK_DEFAULT) #define CORE_DUMP_USE_REGSET #define ELF_EXEC_PAGESIZE PAGE_SIZE -- 2.20.1