From patchwork Fri Nov 17 18:22:01 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Will Deacon X-Patchwork-Id: 10063237 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 790C16023A for ; Fri, 17 Nov 2017 18:27:10 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 69F232A78F for ; Fri, 17 Nov 2017 18:27:10 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 5E7E72ACC6; Fri, 17 Nov 2017 18:27:10 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.2 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,RCVD_IN_DNSWL_MED autolearn=ham version=3.3.1 Received: from bombadil.infradead.org (bombadil.infradead.org [65.50.211.133]) (using TLSv1.2 with cipher AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id E97242A78F for ; Fri, 17 Nov 2017 18:27:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:MIME-Version:Cc:List-Subscribe: List-Help:List-Post:List-Archive:List-Unsubscribe:List-Id:References: In-Reply-To:Message-Id:Date:Subject:To:From:Reply-To:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Owner; bh=A2g2HKi6yqTYxgNlgVgpxnQ0xhzl4g5Fm9wZIOlgmwc=; b=oxSGYknDHAxUsNFVQvB1LiF/lL Lyt86Lm5db26IZDbIvu12nXd28XBmFQ4i0oiU9kbwAq/36yNmn/qjXZo6LR2A6xMH0FTtUw+TEimz 5uGntxHmKlIJ9nmD1XUNxdV2GiHzcI1nzQFCm5u0tA1HM3B3BreHNIwnBkdRN0OG7RyQGdMs+2vsi av/uAgWPXbS0rTUV1ig+XupLHnWIc1J5XVNmghC0zgx7F0Nj4eio6LkIHdpOII8jDu1UR8lKXcJEl ZARZnHvwI4xISqH5lvRdqziRnPYZpjdlLh+bgsN1a6KIJ+s1pqUcsag+aZ9g5SsCzTps0lZgChXrp ziD+muqw==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.87 #1 (Red Hat Linux)) id 1eFlM4-0002yz-VB; Fri, 17 Nov 2017 18:27:09 +0000 Received: from foss.arm.com ([217.140.101.70]) by bombadil.infradead.org with esmtp (Exim 4.87 #1 (Red Hat Linux)) id 1eFlI3-0005vY-FF for linux-arm-kernel@lists.infradead.org; Fri, 17 Nov 2017 18:23:01 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id E1EE61AC1; Fri, 17 Nov 2017 10:21:55 -0800 (PST) Received: from edgewater-inn.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.72.51.249]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id B37463F599; Fri, 17 Nov 2017 10:21:55 -0800 (PST) Received: by edgewater-inn.cambridge.arm.com (Postfix, from userid 1000) id 03F941AE17F5; Fri, 17 Nov 2017 18:22:03 +0000 (GMT) From: Will Deacon To: linux-arm-kernel@lists.infradead.org Subject: [PATCH 18/18] arm64: Kconfig: Add CONFIG_UNMAP_KERNEL_AT_EL0 Date: Fri, 17 Nov 2017 18:22:01 +0000 Message-Id: <1510942921-12564-19-git-send-email-will.deacon@arm.com> X-Mailer: git-send-email 2.1.4 In-Reply-To: <1510942921-12564-1-git-send-email-will.deacon@arm.com> References: <1510942921-12564-1-git-send-email-will.deacon@arm.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20171117_102259_780778_4CB5067D X-CRM114-Status: UNSURE ( 9.97 ) X-CRM114-Notice: Please train this message. X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: mark.rutland@arm.com, keescook@chromium.org, ard.biesheuvel@linaro.org, catalin.marinas@arm.com, dave.hansen@linux.intel.com, sboyd@codeaurora.org, linux-kernel@vger.kernel.org, Will Deacon MIME-Version: 1.0 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Virus-Scanned: ClamAV using ClamSMTP Add a Kconfig entry to control use of the entry trampoline, which allows us to unmap the kernel whilst running in userspace and improve the robustness of KASLR. Signed-off-by: Will Deacon --- arch/arm64/Kconfig | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index f0fcbfc2262e..f99ffb88843a 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -796,6 +796,19 @@ config FORCE_MAX_ZONEORDER However for 4K, we choose a higher default value, 11 as opposed to 10, giving us 4M allocations matching the default size used by generic code. +config UNMAP_KERNEL_AT_EL0 + bool "Unmap kernel when running in userspace (aka \"KAISER\")" + default y + help + Some attacks against KASLR make use of the timing difference between + a permission fault which could arise from a page table entry that is + present in the TLB, and a translation fault which always requires a + page table walk. This option defends against these attacks by unmapping + the kernel whilst running in userspace, therefore forcing translation + faults for all of kernel space. + + If unsure, say Y. + menuconfig ARMV8_DEPRECATED bool "Emulate deprecated/obsolete ARMv8 instructions" depends on COMPAT