From patchwork Mon Feb 10 19:30:43 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Kees Cook X-Patchwork-Id: 11374007 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 8F70A1395 for ; Mon, 10 Feb 2020 19:31:27 +0000 (UTC) Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.kernel.org (Postfix) with SMTP id EC84A20661 for ; Mon, 10 Feb 2020 19:31:25 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b="hvrKfX5Y" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org EC84A20661 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-17762-patchwork-kernel-hardening=patchwork.kernel.org@lists.openwall.com Received: (qmail 11850 invoked by uid 550); 10 Feb 2020 19:31:12 -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 11811 invoked from network); 10 Feb 2020 19:31:12 -0000 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=6noGYPwM3SA0qSn1DjhC04WI3GU5Jbgm29601EFLQxY=; b=hvrKfX5YTyjWi1ypYrma3QUvOIzzwx5eP1e5SWnVM7fYdEB7cTXp0VLscQZXxlorII KASkYlwnUbwRoj+rvzhAZPJR542QwWgAtt0bf9LEgpg4gV9JV9tO3B0r5MmgGnJbfqjc KS/hLBOlgW90PWNOGQmPIgcyzMg0ZELj7LhF8= 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=6noGYPwM3SA0qSn1DjhC04WI3GU5Jbgm29601EFLQxY=; b=Yn8xH3qLHmJSLF5Lig8emJqvKrKUJDHhgpRhR10VF5PFPt7knJyzHwUtBK8t8pBMo/ hB13B8L1lw2gKd1QKvNaxyty8k1CnrXep2e3s2OZMOwqc27ED5l+i/cZkUZwD1VjPRSS Eg1diN4EOPyeApw4z3FFJlf5m1xZfUGOcvAlWb7n/r3+avvJwOv6Tns69lIRCRvMlP3q iCWMNbU3rse5QmKyxZxvjeTLxLIyidnUh612rAC44avcuMs2e1CLK56Qx6BphijoBlj6 w0wKeDj5QjbF7zx5EHgh7LMg/0f+MyRznB+QPVsQp6EsEKlJccJkg7dAIz8y09ifhavu LLZA== X-Gm-Message-State: APjAAAU3DDOsmqTzotPMJ+KuoT2VMWHBAy2nKDti8+0CrJtWsmImgnrd g08QLAEN1dWmsZVh/yuR2rATtQ== X-Google-Smtp-Source: APXvYqzRvao2CNFFWbyoxZWSuc7lKKPgMkVudeHRv3oBDW5/WpFR518lDppuCkgzALOGlW3N5WFORw== X-Received: by 2002:a9d:6289:: with SMTP id x9mr2292404otk.8.1581363059840; Mon, 10 Feb 2020 11:30:59 -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 1/7] x86/elf: Add table to document READ_IMPLIES_EXEC Date: Mon, 10 Feb 2020 11:30:43 -0800 Message-Id: <20200210193049.64362-2-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 Add a table to document the current behavior of READ_IMPLIES_EXEC in preparation for changing the behavior. Signed-off-by: Kees Cook --- arch/x86/include/asm/elf.h | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) diff --git a/arch/x86/include/asm/elf.h b/arch/x86/include/asm/elf.h index 69c0f892e310..733f69c2b053 100644 --- a/arch/x86/include/asm/elf.h +++ b/arch/x86/include/asm/elf.h @@ -281,6 +281,25 @@ extern u32 elf_hwcap2; /* * An executable for which elf_read_implies_exec() returns TRUE will * have the READ_IMPLIES_EXEC personality flag set automatically. + * + * The decision process for determining the results are: + * + *              CPU: | lacks NX*  | has NX, ia32     | has NX, x86_64 | + * ELF:              |            |                  |                | + * -------------------------------|------------------|----------------| + * missing GNU_STACK | exec-all   | exec-all         | exec-all       | + * GNU_STACK == RWX  | exec-all   | exec-all         | exec-all       | + * GNU_STACK == RW   | exec-none  | 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. + * + * *this column has no architectural effect: NX markings are ignored by + * hardware, but may have behavioral effects when "wants X" collides with + * "cannot be X" constraints in memory permission flags, as in + * https://lkml.kernel.org/r/20190418055759.GA3155@mellanox.com + * */ #define elf_read_implies_exec(ex, executable_stack) \ (executable_stack != EXSTACK_DISABLE_X)