From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Cyrus-Session-Id: sloti22d1t05-3369064-1520824139-2-7923106054296696221 X-Sieve: CMU Sieve 3.0 X-Spam-known-sender: no X-Spam-score: 0.0 X-Spam-hits: BAYES_00 -1.9, HEADER_FROM_DIFFERENT_DOMAINS 0.25, ME_NOAUTH 0.01, RCVD_IN_DNSWL_HI -5, T_RP_MATCHES_RCVD -0.01, LANGUAGES en, BAYES_USED global, SA_VERSION 3.4.0 X-Spam-source: IP='209.132.180.67', Host='vger.kernel.org', Country='CN', FromHeader='uk', MailFrom='org' X-Spam-charsets: plain='UTF-8' X-Resolved-to: greg@kroah.com X-Delivered-to: greg@kroah.com X-Mail-from: stable-owner@vger.kernel.org ARC-Seal: i=1; a=rsa-sha256; cv=none; d=messagingengine.com; s=arctest; t=1520824138; b=B819BV5AvjRgS3bswzgyhJGsEsSPDnxecI+5X8MVISEH5hC XtXcJ2uHUvpr790gIJZEVl6pTKxiI5Z3KbrF7AunPwvweBme7eZI4ldSeIFSNdNO I5jwcnbCY4Qwe8mP+KHTvKWEf6h9r/tJwnB/aDAiF3BjgGAFcqq5qupydxT44OHQ dGmobTiTU7keGo974KypkhIRTufJAvvN3F7vB7srE8DrTgHkX4UY8+fZt1WgQp3j fwFg5uEm351SmGISWPEybFDwLmDhE9xHwEK7AHS1a019tJvr89AoMdo2ZZUah9Yz bAAImPaDujks01Jq+9ySQE1vjwhjFjiiHhbZDnQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=content-type:content-transfer-encoding :mime-version:from:to:cc:date:message-id:subject:in-reply-to :sender:list-id; s=arctest; t=1520824138; bh=d+x761UanbI0Ekw/eIF 22Srdby8EdD6sTOTrE1aW3Yw=; b=oYvGTawPmTJX/1+5bn7MSAovy7SNxNM1+J/ NzOJ2lgo/qDYNHMVuf8L4T3HEeSm0kOGyfhaSWzQ43arXbR41TKhh+mKVpRSbDCU oRjdJ6lKYZCcbJqMWRNPmxqoZrvgNP9gXejpuQoUPunWYBMZlcda8rV7HVP5dDZh z4M7v5+LBsEOYAPSH/H3TiG+0spg39ijeRFROtp7MqCm5n4sZbcz063AJY+CdYDm sdazyS63o+YdFRcH/nYgLHX+CWHqo4pFpTjC2MzaB9QzEmNJqHLRr+vp/d7k85RL +rJUZu8xi46hIU69vsj4kg/cKI3h80IGNvCQufTcTM6FympEH9g== ARC-Authentication-Results: i=1; mx4.messagingengine.com; arc=none (no signatures found); dkim=none (no signatures found); dmarc=none (p=none,has-list-id=yes,d=none) header.from=decadent.org.uk; iprev=pass policy.iprev=209.132.180.67 (vger.kernel.org); spf=none smtp.mailfrom=stable-owner@vger.kernel.org smtp.helo=vger.kernel.org; x-aligned-from=fail; x-category=clean score=-100 state=0; x-ptr=pass x-ptr-helo=vger.kernel.org x-ptr-lookup=vger.kernel.org; x-return-mx=pass smtp.domain=vger.kernel.org smtp.result=pass smtp_org.domain=kernel.org smtp_org.result=pass smtp_is_org_domain=no header.domain=decadent.org.uk header.result=pass header_is_org_domain=yes Authentication-Results: mx4.messagingengine.com; arc=none (no signatures found); dkim=none (no signatures found); dmarc=none (p=none,has-list-id=yes,d=none) header.from=decadent.org.uk; iprev=pass policy.iprev=209.132.180.67 (vger.kernel.org); spf=none smtp.mailfrom=stable-owner@vger.kernel.org smtp.helo=vger.kernel.org; x-aligned-from=fail; x-category=clean score=-100 state=0; x-ptr=pass x-ptr-helo=vger.kernel.org x-ptr-lookup=vger.kernel.org; x-return-mx=pass smtp.domain=vger.kernel.org smtp.result=pass smtp_org.domain=kernel.org smtp_org.result=pass smtp_is_org_domain=no header.domain=decadent.org.uk header.result=pass header_is_org_domain=yes Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932821AbeCLDIC (ORCPT ); Sun, 11 Mar 2018 23:08:02 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:41510 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932781AbeCLDHv (ORCPT ); Sun, 11 Mar 2018 23:07:51 -0400 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Borislav Petkov" , "Linus Torvalds" , "H. Peter Anvin" , "Andy Lutomirski" , "Denys Vlasenko" , "Thomas Gleixner" , "Ingo Molnar" , "Borislav Petkov" , "Brian Gerst" Date: Mon, 12 Mar 2018 03:06:12 +0000 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.16 13/76] x86/alternatives: Guard NOPs optimization In-Reply-To: X-SA-Exim-Connect-IP: 2a02:8011:400e:2:6f00:88c8:c921:d332 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: stable-owner@vger.kernel.org X-Mailing-List: stable@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: 3.16.56-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Borislav Petkov commit 69df353ff305805fc16082d0c5bfa6e20fa8b863 upstream. Take a look at the first instruction byte before optimizing the NOP - there might be something else there already, like the ALTERNATIVE_2() in rdtsc_barrier() which NOPs out on AMD even though we just patched in an MFENCE. This happens because the alternatives sees X86_FEATURE_MFENCE_RDTSC, AMD CPUs set it, we patch in the MFENCE and right afterwards it sees X86_FEATURE_LFENCE_RDTSC which AMD CPUs don't set and we blindly optimize the NOP. Checking whether at least the first byte is 0x90 prevents that. Signed-off-by: Borislav Petkov Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1428181662-18020-1-git-send-email-bp@alien8.de Signed-off-by: Ingo Molnar Signed-off-by: Ben Hutchings --- arch/x86/kernel/alternative.c | 3 +++ 1 file changed, 3 insertions(+) --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -325,6 +325,9 @@ done: static void __init_or_module optimize_nops(struct alt_instr *a, u8 *instr) { + if (instr[0] != 0x90) + return; + add_nops(instr + (a->instrlen - a->padlen), a->padlen); DUMP_BYTES(instr, a->instrlen, "%p: [%d:%d) optimized NOPs: ",