From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.kernel.org ([198.145.29.136]:60788 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752872AbcK3Uh6 (ORCPT ); Wed, 30 Nov 2016 15:37:58 -0500 From: Andy Lutomirski To: stable@vger.kernel.org Cc: Matthew Whitehead , Greg KH , Andy Lutomirski , "H . Peter Anvin" Subject: [PATCH BACKPORT 3.4 - 4.5] x86/traps: Ignore high word of regs->cs in early_idt_handler_common Date: Wed, 30 Nov 2016 12:37:53 -0800 Message-Id: Sender: stable-owner@vger.kernel.org List-ID: This is a backport of: commit cb32c69920e58a1a58e7b5cad975038a69c0ce7d 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 commit 1e02ce4cccdc ("x86: Store a per-cpu shadow copy of CR4") and commit 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 Cc: stable@vger.kernel.org Reported-by: Matthew Whitehead Signed-off-by: Andy Lutomirski --- arch/x86/kernel/head_32.S | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/kernel/head_32.S b/arch/x86/kernel/head_32.S index af1112980dd4..99373aa0762a 100644 --- 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 -- 2.9.3