From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:42570 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754485AbbJRCa4 (ORCPT ); Sat, 17 Oct 2015 22:30:56 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Thomas Gleixner , "Richard W.M. Jones" , Chuck Ebbert , Borislav Petkov Subject: [PATCH 4.1 039/202] x86/alternatives: Make optimize_nops() interrupt safe and synced Date: Sat, 17 Oct 2015 18:57:02 -0700 Message-Id: <20151018014903.765998745@linuxfoundation.org> In-Reply-To: <20151018014901.946875729@linuxfoundation.org> References: <20151018014901.946875729@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Sender: stable-owner@vger.kernel.org List-ID: 4.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Thomas Gleixner commit 66c117d7fa2ae429911e60d84bf31a90b2b96189 upstream. 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 Link: http://lkml.kernel.org/r/alpine.DEB.2.11.1509031232340.15006@nanos Signed-off-by: Thomas Gleixner Signed-off-by: Greg Kroah-Hartman --- arch/x86/kernel/alternative.c | 5 +++++ 1 file changed, 5 insertions(+) --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -325,10 +325,15 @@ 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);