From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:33292 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752560AbcLFUbZ (ORCPT ); Tue, 6 Dec 2016 15:31:25 -0500 Subject: Patch "arm64: mm: Set PSTATE.PAN from the cpu_enable_pan() call" has been added to the 4.4-stable tree To: james.morse@arm.com, anthony.thompson@arm.com, gregkh@linuxfoundation.org, vladimir.murzin@arm.com, will.deacon@arm.com Cc: , From: Date: Tue, 06 Dec 2016 21:23:27 +0100 Message-ID: <1481055807155179@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: This is a note to let you know that I've just added the patch titled arm64: mm: Set PSTATE.PAN from the cpu_enable_pan() call to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: arm64-mm-set-pstate.pan-from-the-cpu_enable_pan-call.patch and it can be found in the queue-4.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let know about it. >>From 7209c868600bd8926e37c10b9aae83124ccc1dd8 Mon Sep 17 00:00:00 2001 From: James Morse Date: Tue, 18 Oct 2016 11:27:47 +0100 Subject: arm64: mm: Set PSTATE.PAN from the cpu_enable_pan() call 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 @@ -608,7 +610,14 @@ asmlinkage int __exception do_debug_exce #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 */ Patches currently in stable-queue which might be from james.morse@arm.com are queue-4.4/arm64-mm-set-pstate.pan-from-the-cpu_enable_pan-call.patch queue-4.4/arm64-suspend-reconfigure-pstate-after-resume-from-idle.patch queue-4.4/arm64-cpufeature-schedule-enable-calls-instead-of-calling-them-via-ipi.patch