From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:48124 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760313AbcLBRKn (ORCPT ); Fri, 2 Dec 2016 12:10:43 -0500 Subject: Patch "x86/traps: Ignore high word of regs->cs in early_fixup_exception()" has been added to the 4.4-stable tree To: luto@kernel.org, gregkh@linuxfoundation.org, hpa@zytor.com, tedheadster@gmail.com Cc: , From: Date: Fri, 02 Dec 2016 18:10:42 +0100 Message-ID: <148069864283254@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/traps: Ignore high word of regs->cs in early_fixup_exception() 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: x86-traps-ignore-high-word-of-regs-cs-in-early_fixup_exception.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 fc0e81b2bea0ebceb71889b61d2240856141c9ee Mon Sep 17 00:00:00 2001 From: Andy Lutomirski Date: Sat, 19 Nov 2016 18:42:40 -0800 Subject: x86/traps: Ignore high word of regs->cs in early_fixup_exception() From: Andy Lutomirski commit fc0e81b2bea0ebceb71889b61d2240856141c9ee upstream. On the 80486 DX, it seems that some exceptions may leave garbage in the high bits of CS. This causes sporadic failures in which early_fixup_exception() refuses to fix up an exception. As far as I can tell, this has been buggy for a long time, but the problem seems to have been exacerbated by commits: 1e02ce4cccdc ("x86: Store a per-cpu shadow copy of CR4") e1bfc11c5a6f ("x86/init: Fix cr4_init_shadow() on CR4-less machines") This appears to have broken for as long as we've had early exception handling. [ This backport should apply to kernels from 3.4 - 4.5. ] Fixes: 4c5023a3fa2e ("x86-32: Handle exception table entries during early boot") Cc: H. Peter Anvin Reported-by: Matthew Whitehead Signed-off-by: Andy Lutomirski Signed-off-by: Greg Kroah-Hartman --- arch/x86/kernel/head_32.S | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/arch/x86/kernel/head_32.S +++ b/arch/x86/kernel/head_32.S @@ -571,7 +571,7 @@ early_idt_handler_common: movl %eax,%ds movl %eax,%es - cmpl $(__KERNEL_CS),32(%esp) + cmpw $(__KERNEL_CS),32(%esp) jne 10f leal 28(%esp),%eax # Pointer to %eip Patches currently in stable-queue which might be from luto@kernel.org are queue-4.4/x86-traps-ignore-high-word-of-regs-cs-in-early_fixup_exception.patch