Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935107AbcLMT62 (ORCPT ); Tue, 13 Dec 2016 14:58:28 -0500 Received: from mx2.suse.de ([195.135.220.15]:54234 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S935243AbcLMTxR (ORCPT ); Tue, 13 Dec 2016 14:53:17 -0500 X-Amavis-Alert: BAD HEADER SECTION, Duplicate header field: "References" From: Jiri Slaby To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Andy Lutomirski , "H . Peter Anvin" , Jiri Slaby Subject: [PATCH 3.12 20/38] x86/traps: Ignore high word of regs->cs in early_fixup_exception() Date: Tue, 13 Dec 2016 20:52:46 +0100 Message-Id: X-Mailer: git-send-email 2.11.0 In-Reply-To: <15034b96ec06ee859b67c6cd4e3be569a4ef286b.1481658746.git.jslaby@suse.cz> References: <15034b96ec06ee859b67c6cd4e3be569a4ef286b.1481658746.git.jslaby@suse.cz> In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1495 Lines: 47 From: Andy Lutomirski 3.12-stable review patch. If anyone has any objections, please let me know. =============== 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: Jiri Slaby --- 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 30a2aa3782fa..879e67acf463 100644 --- a/arch/x86/kernel/head_32.S +++ b/arch/x86/kernel/head_32.S @@ -564,7 +564,7 @@ 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 -- 2.11.0