From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:41004 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753223AbbJMWCy (ORCPT ); Tue, 13 Oct 2015 18:02:54 -0400 Subject: Patch "x86/nmi/64: Fix a paravirt stack-clobbering bug in the NMI code" has been added to the 4.1-stable tree To: luto@kernel.org, gregkh@linuxfoundation.org, sasha.levin@oracle.com, tglx@linutronix.de Cc: , From: Date: Tue, 13 Oct 2015 15:02:52 -0700 Message-ID: <1444773772106202@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 x86/nmi/64: Fix a paravirt stack-clobbering bug in the NMI code to the 4.1-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: x86-nmi-64-fix-a-paravirt-stack-clobbering-bug-in-the-nmi-code.patch and it can be found in the queue-4.1 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let know about it. >>From 83c133cf11fb0e68a51681447e372489f052d40e Mon Sep 17 00:00:00 2001 From: Andy Lutomirski Date: Sun, 20 Sep 2015 16:32:05 -0700 Subject: x86/nmi/64: Fix a paravirt stack-clobbering bug in the NMI code From: Andy Lutomirski commit 83c133cf11fb0e68a51681447e372489f052d40e upstream. The NMI entry code that switches to the normal kernel stack needs to be very careful not to clobber any extra stack slots on the NMI stack. The code is fine under the assumption that SWAPGS is just a normal instruction, but that assumption isn't really true. Use SWAPGS_UNSAFE_STACK instead. This is part of a fix for some random crashes that Sasha saw. Fixes: 9b6e6a8334d5 ("x86/nmi/64: Switch stacks on userspace NMI entry") Reported-and-tested-by: Sasha Levin Signed-off-by: Andy Lutomirski Link: http://lkml.kernel.org/r/974bc40edffdb5c2950a5c4977f821a446b76178.1442791737.git.luto@kernel.org Signed-off-by: Thomas Gleixner Signed-off-by: Greg Kroah-Hartman --- arch/x86/kernel/entry_64.S | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) --- a/arch/x86/kernel/entry_64.S +++ b/arch/x86/kernel/entry_64.S @@ -1456,9 +1456,12 @@ ENTRY(nmi) * we don't want to enable interrupts, because then we'll end * up in an awkward situation in which IRQs are on but NMIs * are off. + * + * We also must not push anything to the stack before switching + * stacks lest we corrupt the "NMI executing" variable. */ - SWAPGS + SWAPGS_UNSAFE_STACK cld movq %rsp, %rdx movq PER_CPU_VAR(kernel_stack), %rsp Patches currently in stable-queue which might be from luto@kernel.org are queue-4.1/x86-paravirt-replace-the-paravirt-nop-with-a-bona-fide-empty-function.patch queue-4.1/x86-nmi-64-fix-a-paravirt-stack-clobbering-bug-in-the-nmi-code.patch