From patchwork Fri Aug 12 15:27:45 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Catalin Marinas X-Patchwork-Id: 9277291 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 CEFE560752 for ; Fri, 12 Aug 2016 15:28:52 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id C16AE28A52 for ; Fri, 12 Aug 2016 15:28:52 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id B5BB428A57; Fri, 12 Aug 2016 15:28:52 +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, RCVD_IN_DNSWL_MED autolearn=ham version=3.3.1 Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.wl.linuxfoundation.org (Postfix) with SMTP id C995A28A52 for ; Fri, 12 Aug 2016 15:28:51 +0000 (UTC) Received: (qmail 1831 invoked by uid 550); 12 Aug 2016 15:28:32 -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: Reply-To: kernel-hardening@lists.openwall.com Delivered-To: mailing list kernel-hardening@lists.openwall.com Received: (qmail 32400 invoked from network); 12 Aug 2016 15:28:22 -0000 From: Catalin Marinas To: linux-arm-kernel@lists.infradead.org Cc: kernel-hardening@lists.openwall.com, Julien Grall , Will Deacon , James Morse , Kees Cook Date: Fri, 12 Aug 2016 16:27:45 +0100 Message-Id: <1471015666-23125-7-git-send-email-catalin.marinas@arm.com> X-Mailer: git-send-email 2.1.4 In-Reply-To: <1471015666-23125-1-git-send-email-catalin.marinas@arm.com> References: <1471015666-23125-1-git-send-email-catalin.marinas@arm.com> Subject: [kernel-hardening] [PATCH 6/7] arm64: xen: Enable user access before a privcmd hvc call X-Virus-Scanned: ClamAV using ClamSMTP Privcmd calls are issued by the userspace. The kernel needs to enable access to TTBR0_EL1 as the hypervisor would issue stage 1 translations to user memory via AT instructions. Since AT instructions are not affected by the PAN bit (ARMv8.1), we only need the explicit uaccess_enable/disable if the TTBR0 PAN option is enabled. Cc: Julien Grall Cc: Will Deacon Cc: James Morse Cc: Kees Cook Signed-off-by: Catalin Marinas Reviewed-by: Julien Grall Acked-by: Stefano Stabellini --- arch/arm64/xen/hypercall.S | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) diff --git a/arch/arm64/xen/hypercall.S b/arch/arm64/xen/hypercall.S index 329c8027b0a9..4c509f4f4dcc 100644 --- a/arch/arm64/xen/hypercall.S +++ b/arch/arm64/xen/hypercall.S @@ -91,6 +91,24 @@ ENTRY(privcmd_call) mov x2, x3 mov x3, x4 mov x4, x5 +#ifdef CONFIG_ARM64_TTBR0_PAN + /* + * Privcmd calls are issued by the userspace. The kernel needs to + * enable access to TTBR0_EL1 as the hypervisor would issue stage 1 + * translations to user memory via AT instructions. Since AT + * instructions are not affected by the PAN bit (ARMv8.1), we only + * need the explicit uaccess_enable/disable if the TTBR0 PAN option is + * enabled. + */ + uaccess_enable x6, x7, x8 +#endif hvc XEN_IMM + +#ifdef CONFIG_ARM64_TTBR0_PAN + /* + * Disable userspace access from kernel once the hyp call completed. + */ + uaccess_disable x6 +#endif ret ENDPROC(privcmd_call);