From patchwork Fri Sep 11 16:25:59 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Julien Grall X-Patchwork-Id: 7162551 Return-Path: X-Original-To: patchwork-linux-arm@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork1.web.kernel.org (Postfix) with ESMTP id 6FD359F380 for ; Fri, 11 Sep 2015 16:44:29 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 82BE5206D7 for ; Fri, 11 Sep 2015 16:44:28 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.9]) (using TLSv1.2 with cipher AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 97A63206BD for ; Fri, 11 Sep 2015 16:44:27 +0000 (UTC) Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1ZaRPB-00027R-MM; Fri, 11 Sep 2015 16:42:29 +0000 Received: from smtp02.citrix.com ([66.165.176.63]) by bombadil.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1ZaRP5-0001Yz-Sr for linux-arm-kernel@lists.infradead.org; Fri, 11 Sep 2015 16:42:25 +0000 X-IronPort-AV: E=Sophos;i="5.17,511,1437436800"; d="scan'208";a="303033082" From: Julien Grall To: Subject: [PATCH v2] arm/xen: Enable user access to the kernel before issuing a privcmd call Date: Fri, 11 Sep 2015 17:25:59 +0100 Message-ID: <1441988759-4572-1-git-send-email-julien.grall@citrix.com> X-Mailer: git-send-email 2.1.4 MIME-Version: 1.0 X-DLP: MIA2 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20150911_094224_229434_27E6F8E6 X-CRM114-Status: GOOD ( 13.08 ) X-Spam-Score: -4.2 (----) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Russell King , ian.campbell@citrix.com, stefano.stabellini@eu.citrix.com, Riku Voipio , linux-kernel@vger.kernel.org, Julien Grall , linux-arm-kernel@lists.infradead.org Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Spam-Status: No, score=-4.2 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_MED, T_RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP When Xen is copying data to/from the guest it will check if the kernel has the right to do the access. If not, the hypercall will return an error. After the commit a5e090acbf545c0a3b04080f8a488b17ec41fe02 "ARM: software-based privileged-no-access support", the kernel can't access any longer the user space by default. This will result to fail on every hypercall made by the userspace (i.e via privcmd). We have to enable the userspace access and then restore the correct permission every time the privcmd is used to made an hypercall. I didn't find generic helpers to do a these operations, so the change is only arm32 specific. Reported-by: Riku Voipio Signed-off-by: Julien Grall Acked-by: Russell King Acked-by: Stefano Stabellini --- Cc: Stefano Stabellini Cc: Russell King Changes in v2: - Directly enable/disable the user space access in assembly - Typoes ARM64 doesn't seem to have priviledge no-access support yet so there is nothing to do for now. I haven't look x86 at all. --- arch/arm/xen/hypercall.S | 15 +++++++++++++++ 1 file changed, 15 insertions(+) diff --git a/arch/arm/xen/hypercall.S b/arch/arm/xen/hypercall.S index f00e080..10fd99c 100644 --- a/arch/arm/xen/hypercall.S +++ b/arch/arm/xen/hypercall.S @@ -98,8 +98,23 @@ ENTRY(privcmd_call) mov r1, r2 mov r2, r3 ldr r3, [sp, #8] + /* + * Privcmd calls are issued by the userspace. We need to allow the + * kernel to access the userspace memory before issuing the hypercall. + */ + uaccess_enable r4 + + /* r4 is loaded now as we use it as scratch register before */ ldr r4, [sp, #4] __HVC(XEN_IMM) + + /* + * Disable userspace access from kernel. This is fine to do it + * unconditionally as no set_fs(KERNEL_DS)/set_fs(get_ds()) is + * called before. + */ + uaccess_disable r4 + ldm sp!, {r4} ret lr ENDPROC(privcmd_call);