From patchwork Fri Oct 11 00:06:09 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kees Cook X-Patchwork-Id: 11184683 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 9BCF11575 for ; Fri, 11 Oct 2019 00:13:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7B94C21929 for ; Fri, 11 Oct 2019 00:13:23 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b="TKF/H7IX" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727593AbfJKANX (ORCPT ); Thu, 10 Oct 2019 20:13:23 -0400 Received: from mail-pf1-f195.google.com ([209.85.210.195]:44085 "EHLO mail-pf1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727688AbfJKANB (ORCPT ); Thu, 10 Oct 2019 20:13:01 -0400 Received: by mail-pf1-f195.google.com with SMTP id q21so4931421pfn.11 for ; Thu, 10 Oct 2019 17:13:01 -0700 (PDT) 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; bh=Wn91QvvOWXGcdAukdBFPOsAS+V9wjbJFfxE/dszqFsM=; b=TKF/H7IXE7UJDzb3rMUleub9owN4KR+Kc5MridCe/6j0nlzZqoEI/zttKy0QHihDrJ 2ZeHmtUNHexo6bQLRtT0gDvTipRD0K5TGW8Q7FVWpvhcmLBUGnPT1TySO+nYDUITKTZu 3WNoDW0bVMFt0uCMT6eBCSnH00RkY54ViUTLk= 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; bh=Wn91QvvOWXGcdAukdBFPOsAS+V9wjbJFfxE/dszqFsM=; b=XXYmnvcTRBr4gEHdiQN0CNcVY8iSmXw2mRgQifeNHMypTP4cUJV/YaB+KyKs3UvE0I i2YOekezCVIvEkNesV0CDfYDuBkUhCHubpQ9y3+JtPqoKmO4Eh7n6VAib5eAFkbuxR0G dYoHcHIw4xiZ8SzqY8fATfEV9kv2FjVpbKRxtksL1ENJySGV5dKwnicsWWbykoG2w8YS Eq5d/bfTwycCML703B/h4Je2LUyZCsJjQ429fAKoNt9yyGP8idMdzEptJNG3a8w5eV16 CkVMWaMfuzr5NAz6TA+4SC1arX3tHR/vNfbj1SA3ERZ4pdNQU9xodwSuLUVBFwPolLJh bsvg== X-Gm-Message-State: APjAAAWIyHrBVBV9NPZNM4z8g17rqBwJFH7FgGht7j2wBogTOE2H3eGL CpRk22IdNM0XMgaPhJQwoGUOUA== X-Google-Smtp-Source: APXvYqwhzx8QmNWMryCruzS69inQpCD817u3s0gzfMeJwk1Bb2iOQgca7Hto534MUkNuyGvUJAkyfA== X-Received: by 2002:a17:90a:ff0f:: with SMTP id ce15mr14913883pjb.14.1570752780484; Thu, 10 Oct 2019 17:13:00 -0700 (PDT) Received: from www.outflux.net (smtp.outflux.net. [198.145.64.163]) by smtp.gmail.com with ESMTPSA id y144sm7993803pfb.188.2019.10.10.17.12.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 10 Oct 2019 17:12:56 -0700 (PDT) From: Kees Cook To: Borislav Petkov Cc: Kees Cook , Rick Edgecombe , Dave Hansen , Andy Lutomirski , Arnd Bergmann , Michael Ellerman , Heiko Carstens , Will Deacon , linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, linux-alpha@vger.kernel.org, linux-ia64@vger.kernel.org, linux-s390@vger.kernel.org, linux-c6x-dev@linux-c6x.org, Yoshinori Sato , Michal Simek , linux-parisc@vger.kernel.org, linux-xtensa@linux-xtensa.org, x86@kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v2 29/29] x86: Use INT3 instead of NOP for linker fill bytes Date: Thu, 10 Oct 2019 17:06:09 -0700 Message-Id: <20191011000609.29728-30-keescook@chromium.org> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20191011000609.29728-1-keescook@chromium.org> References: <20191011000609.29728-1-keescook@chromium.org> Sender: linux-parisc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-parisc@vger.kernel.org Instead of using 0x90 (NOP) to fill bytes between functions, which makes it easier to sloppily target functions in function pointer overwrite attacks, fill with 0xCC (INT3) to force a trap. Also drop the space between "=" and the value to better match the binutils documentation https://sourceware.org/binutils/docs/ld/Output-Section-Fill.html#Output-Section-Fill Example "objdump -d" before: ... ffffffff810001e0 : ffffffff810001e0: 48 8b 25 e1 b1 51 01 mov 0x151b1e1(%rip),%rsp # ffffffff8251b3c8 ffffffff810001e7: e9 d5 fe ff ff jmpq ffffffff810000c1 ffffffff810001ec: 90 nop ffffffff810001ed: 90 nop ffffffff810001ee: 90 nop ffffffff810001ef: 90 nop ffffffff810001f0 <__startup_64>: ... After: ... ffffffff810001e0 : ffffffff810001e0: 48 8b 25 41 79 53 01 mov 0x1537941(%rip),%rsp # ffffffff82537b28 ffffffff810001e7: e9 d5 fe ff ff jmpq ffffffff810000c1 ffffffff810001ec: cc int3 ffffffff810001ed: cc int3 ffffffff810001ee: cc int3 ffffffff810001ef: cc int3 ffffffff810001f0 <__startup_64>: ... Signed-off-by: Kees Cook --- arch/x86/kernel/vmlinux.lds.S | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S index b06d6e1188de..3a1a819da137 100644 --- a/arch/x86/kernel/vmlinux.lds.S +++ b/arch/x86/kernel/vmlinux.lds.S @@ -144,7 +144,7 @@ SECTIONS *(.text.__x86.indirect_thunk) __indirect_thunk_end = .; #endif - } :text = 0x9090 + } :text =0xcccc /* End of text section, which should occupy whole number of pages */ _etext = .;