From patchwork Tue Sep 13 17:46:36 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Catalin Marinas X-Patchwork-Id: 9329671 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 42378607FD for ; Tue, 13 Sep 2016 17:47:40 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 3511F29510 for ; Tue, 13 Sep 2016 17:47:40 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 25FA32951E; Tue, 13 Sep 2016 17:47:40 +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 2A6A629510 for ; Tue, 13 Sep 2016 17:47:38 +0000 (UTC) Received: (qmail 7196 invoked by uid 550); 13 Sep 2016 17:47:19 -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 5628 invoked from network); 13 Sep 2016 17:47:14 -0000 From: Catalin Marinas To: linux-arm-kernel@lists.infradead.org Cc: Will Deacon , James Morse , Kees Cook , Mark Rutland , Ard Biesheuvel , AKASHI Takahiro , kernel-hardening@lists.openwall.com Date: Tue, 13 Sep 2016 18:46:36 +0100 Message-Id: <1473788797-10879-7-git-send-email-catalin.marinas@arm.com> X-Mailer: git-send-email 2.1.4 In-Reply-To: <1473788797-10879-1-git-send-email-catalin.marinas@arm.com> References: <1473788797-10879-1-git-send-email-catalin.marinas@arm.com> Subject: [kernel-hardening] [PATCH v3 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. Reviewed-by: Julien Grall Acked-by: Stefano Stabellini Cc: Will Deacon Cc: James Morse Cc: Kees Cook Cc: Mark Rutland Signed-off-by: Catalin Marinas --- arch/arm64/xen/hypercall.S | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) diff --git a/arch/arm64/xen/hypercall.S b/arch/arm64/xen/hypercall.S index 329c8027b0a9..a23b2e8f2647 100644 --- a/arch/arm64/xen/hypercall.S +++ b/arch/arm64/xen/hypercall.S @@ -49,6 +49,7 @@ #include #include +#include #include @@ -91,6 +92,24 @@ ENTRY(privcmd_call) mov x2, x3 mov x3, x4 mov x4, x5 +#ifdef CONFIG_ARM64_SW_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 emulation + * is enabled (it implies that hardware UAO and PAN disabled). + */ + uaccess_enable_not_uao x6, x7 +#endif hvc XEN_IMM + +#ifdef CONFIG_ARM64_SW_TTBR0_PAN + /* + * Disable userspace access from kernel once the hyp call completed. + */ + uaccess_disable_not_uao x6 +#endif ret ENDPROC(privcmd_call);