From patchwork Thu Apr 16 11:24:30 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mark Brown X-Patchwork-Id: 227949 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=-10.1 required=3.0 tests=DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable 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 0851BC2BB55 for ; Thu, 16 Apr 2020 11:25:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C2C0221841 for ; Thu, 16 Apr 2020 11:25:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1587036357; bh=wCkxcDbz5xirgIfchefcfaOqkTclgC7v7IQAWBE+wHA=; h=From:To:Cc:Subject:Date:List-ID:From; b=RIWuEEOmDkfHo5gRBhjLX36gvrjWLfhQDGBOiIk+WxFViGjZD0VarRlOmijV9vA5+ 2Col8353Y0GwtT6FerTfrvheaHL1FeFlMJge5H2dm6dwpvoDCSBJYGQe060edFK8xn tA9CCHCuS+yOrezK/P1zq3c2OKDI83IleFJdktKw= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2632937AbgDPLZu (ORCPT ); Thu, 16 Apr 2020 07:25:50 -0400 Received: from mail.kernel.org ([198.145.29.99]:51068 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2633052AbgDPLZm (ORCPT ); Thu, 16 Apr 2020 07:25:42 -0400 Received: from localhost (fw-tnat.cambridge.arm.com [217.140.96.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id A6D5F21D7F; Thu, 16 Apr 2020 11:25:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1587036342; bh=wCkxcDbz5xirgIfchefcfaOqkTclgC7v7IQAWBE+wHA=; h=From:To:Cc:Subject:Date:From; b=a3qrk9JHogGqtwuY+xnShuARonqZlEi1RWr6VSTITPvJSd0TOTKyZPg/+mWutHW22 Qad9z+CS/uYO0ptdC+XUF2jbyp48zfQw6zLeoBDlXDY25EkVggcV3XZX2Ta+FfGI7U VCP2sWVMgIczYJcMxZo7IZfYelZ3r0J5kNt1tQZ8= From: Mark Brown To: stable@vger.kernel.org, gregkh@linuxfoundation.org Cc: linux-arm-kernel@lists.infradead.org, Mark Brown , Szabolcs Nagy , Catalin Marinas Subject: [PATCH 5.6] arm64: Always force a branch protection mode when the compiler has one Date: Thu, 16 Apr 2020 12:24:30 +0100 Message-Id: <20200416112430.1256-1-broonie@kernel.org> X-Mailer: git-send-email 2.20.1 MIME-Version: 1.0 Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org Compilers with branch protection support can be configured to enable it by default, it is likely that distributions will do this as part of deploying branch protection system wide. As well as the slight overhead from having some extra NOPs for unused branch protection features this can cause more serious problems when the kernel is providing pointer authentication to userspace but not built for pointer authentication itself. In that case our switching of keys for userspace can affect the kernel unexpectedly, causing pointer authentication instructions in the kernel to corrupt addresses. To ensure that we get consistent and reliable behaviour always explicitly initialise the branch protection mode, ensuring that the kernel is built the same way regardless of the compiler defaults. [This is a reworked version of b8fdef311a0bd9223f1075 ("arm64: Always force a branch protection mode when the compiler has one") for backport. Kernels prior to 74afda4016a7 ("arm64: compile the kernel with ptrauth return address signing") don't have any Makefile machinery for forcing on pointer auth but still have issues if the compiler defaults it on so need this reworked version. -- broonie] Fixes: 7503197562567 (arm64: add basic pointer authentication support) Reported-by: Szabolcs Nagy Signed-off-by: Mark Brown Cc: stable@vger.kernel.org [catalin.marinas@arm.com: remove Kconfig option in favour of Makefile check] Signed-off-by: Catalin Marinas --- arch/arm64/Makefile | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile index dca1a97751ab..4e6ce2d9196e 100644 --- a/arch/arm64/Makefile +++ b/arch/arm64/Makefile @@ -65,6 +65,10 @@ stack_protector_prepare: prepare0 include/generated/asm-offsets.h)) endif +# Ensure that if the compiler supports branch protection we default it +# off. +KBUILD_CFLAGS += $(call cc-option,-mbranch-protection=none) + ifeq ($(CONFIG_CPU_BIG_ENDIAN), y) KBUILD_CPPFLAGS += -mbig-endian CHECKFLAGS += -D__AARCH64EB__