Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932353AbcLGHKV (ORCPT ); Wed, 7 Dec 2016 02:10:21 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:58418 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932329AbcLGHKN (ORCPT ); Wed, 7 Dec 2016 02:10:13 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Tony Thompson , Vladimir Murzin , James Morse , Will Deacon Subject: [PATCH 4.8 34/35] arm64: mm: Set PSTATE.PAN from the cpu_enable_pan() call Date: Wed, 7 Dec 2016 08:08:50 +0100 Message-Id: <20161207070724.113125260@linuxfoundation.org> X-Mailer: git-send-email 2.10.2 In-Reply-To: <20161207070722.410336250@linuxfoundation.org> References: <20161207070722.410336250@linuxfoundation.org> User-Agent: quilt/0.65 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1843 Lines: 59 4.8-stable review patch. If anyone has any objections, please let me know. ------------------ From: James Morse commit 7209c868600bd8926e37c10b9aae83124ccc1dd8 upstream. Commit 338d4f49d6f7 ("arm64: kernel: Add support for Privileged Access Never") enabled PAN by enabling the 'SPAN' feature-bit in SCTLR_EL1. This means the PSTATE.PAN bit won't be set until the next return to the kernel from userspace. On a preemptible kernel we may schedule work that accesses userspace on a CPU before it has done this. Now that cpufeature enable() calls are scheduled via stop_machine(), we can set PSTATE.PAN from the cpu_enable_pan() call. Add WARN_ON_ONCE(in_interrupt()) to check the PSTATE value we updated is not immediately discarded. Reported-by: Tony Thompson Reported-by: Vladimir Murzin Signed-off-by: James Morse [will: fixed typo in comment] Signed-off-by: Will Deacon Signed-off-by: Greg Kroah-Hartman --- arch/arm64/mm/fault.c | 9 +++++++++ 1 file changed, 9 insertions(+) --- a/arch/arm64/mm/fault.c +++ b/arch/arm64/mm/fault.c @@ -29,7 +29,9 @@ #include #include #include +#include +#include #include #include #include @@ -673,7 +675,14 @@ NOKPROBE_SYMBOL(do_debug_exception); #ifdef CONFIG_ARM64_PAN int cpu_enable_pan(void *__unused) { + /* + * We modify PSTATE. This won't work from irq context as the PSTATE + * is discarded once we return from the exception. + */ + WARN_ON_ONCE(in_interrupt()); + config_sctlr_el1(SCTLR_EL1_SPAN, 0); + asm(SET_PSTATE_PAN(1)); return 0; } #endif /* CONFIG_ARM64_PAN */