From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755356AbbICTb3 (ORCPT ); Thu, 3 Sep 2015 15:31:29 -0400 Received: from terminus.zytor.com ([198.137.202.10]:43571 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752810AbbICTb1 (ORCPT ); Thu, 3 Sep 2015 15:31:27 -0400 Date: Thu, 3 Sep 2015 12:30:47 -0700 From: tip-bot for Thomas Gleixner Message-ID: Cc: bp@alien8.de, mingo@kernel.org, rjones@redhat.com, hpa@zytor.com, tglx@linutronix.de, linux-kernel@vger.kernel.org, cebbert.lkml@gmail.com Reply-To: mingo@kernel.org, rjones@redhat.com, bp@alien8.de, cebbert.lkml@gmail.com, linux-kernel@vger.kernel.org, hpa@zytor.com, tglx@linutronix.de In-Reply-To: References: To: linux-tip-commits@vger.kernel.org Subject: [tip:x86/urgent] x86/alternatives: Make optimize_nops() interrupt safe and synced Git-Commit-ID: 66c117d7fa2ae429911e60d84bf31a90b2b96189 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 66c117d7fa2ae429911e60d84bf31a90b2b96189 Gitweb: http://git.kernel.org/tip/66c117d7fa2ae429911e60d84bf31a90b2b96189 Author: Thomas Gleixner AuthorDate: Thu, 3 Sep 2015 12:34:55 +0200 Committer: Thomas Gleixner CommitDate: Thu, 3 Sep 2015 21:27:47 +0200 x86/alternatives: Make optimize_nops() interrupt safe and synced Richard reported the following crash: [ 0.036000] BUG: unable to handle kernel paging request at 55501e06 [ 0.036000] IP: [] common_interrupt+0xb/0x38 [ 0.036000] Call Trace: [ 0.036000] [] ? add_nops+0x90/0xa0 [ 0.036000] [] apply_alternatives+0x274/0x630 Chuck decoded: " 0: 8d 90 90 83 04 24 lea 0x24048390(%eax),%edx 6: 80 fc 0f cmp $0xf,%ah 9: a8 0f test $0xf,%al >> b: a0 06 1e 50 55 mov 0x55501e06,%al 10: 57 push %edi 11: 56 push %esi Interrupt 0x30 occurred while the alternatives code was replacing the initial 0x90,0x90,0x90 NOPs (from the ASM_CLAC macro) with the optimized version, 0x8d,0x76,0x00. Only the first byte has been replaced so far, and it makes a mess out of the insn decoding." optimize_nops() is buggy in two aspects: - It's not disabling interrupts across the modification - It's lacking a sync_core() call Add both. Fixes: 4fd4b6e5537c 'x86/alternatives: Use optimized NOPs for padding' Reported-and-tested-by: "Richard W.M. Jones" Signed-off-by: Thomas Gleixner Cc: Richard W.M. Jones Cc: Chuck Ebbert Cc: Borislav Petkov Cc: stable@vger.kernel.org Link: http://lkml.kernel.org/r/alpine.DEB.2.11.1509031232340.15006@nanos Signed-off-by: Thomas Gleixner --- arch/x86/kernel/alternative.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c index c42827e..25f9093 100644 --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -338,10 +338,15 @@ done: static void __init_or_module optimize_nops(struct alt_instr *a, u8 *instr) { + unsigned long flags; + if (instr[0] != 0x90) return; + local_irq_save(flags); add_nops(instr + (a->instrlen - a->padlen), a->padlen); + sync_core(); + local_irq_restore(flags); DUMP_BYTES(instr, a->instrlen, "%p: [%d:%d) optimized NOPs: ", instr, a->instrlen - a->padlen, a->padlen);