From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-12.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 10397C072B5 for ; Fri, 24 May 2019 08:00:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CCE4620879 for ; Fri, 24 May 2019 08:00:09 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=zytor.com header.i=@zytor.com header.b="vl27+EdK" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389246AbfEXIAJ (ORCPT ); Fri, 24 May 2019 04:00:09 -0400 Received: from terminus.zytor.com ([198.137.202.136]:34235 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388996AbfEXIAI (ORCPT ); Fri, 24 May 2019 04:00:08 -0400 Received: from terminus.zytor.com (localhost [127.0.0.1]) by terminus.zytor.com (8.15.2/8.15.2) with ESMTPS id x4O7xOm5115005 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NO); Fri, 24 May 2019 00:59:24 -0700 DKIM-Filter: OpenDKIM Filter v2.11.0 terminus.zytor.com x4O7xOm5115005 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zytor.com; s=2019051801; t=1558684764; bh=gR+sVOfv9g9vi8Nv64InJyGxDz7fDw8ERv85hAVYXQM=; h=Date:From:Cc:Reply-To:In-Reply-To:References:To:Subject:From; b=vl27+EdKwkCt1uJzIw81rFHxSzKLBrXtPvlzcQqMpU7k4gV+1BYK6s3ATZBRrKu00 7SbMQ2Yzz6ZqG5QNfSGXuABEuRsd+LpY6BsMJjkkPKunoTqx7v10YG7SfDuQbsR/d3 dFzdfmK/Mm+eqxQZI0mQFRdrfw9CUd6VB5O/nZeiBFD80wAwWtcZUIoNjZywd8em8/ ooW/q2X5Hbh123QICvlbr7FwGHoNj6Bebr6SqtvJqkeQXgPYnYCd4hVbStQb8YgH30 xQL2ATxHti+1kuzdhwTwmM+Xfs3peWwcrcULISqpa3/H+Ju6fjT5Zyz1j8KWYNCuEh vpuRKiBULN8XQ== Received: (from tipbot@localhost) by terminus.zytor.com (8.15.2/8.15.2/Submit) id x4O7xN0J115002; Fri, 24 May 2019 00:59:23 -0700 Date: Fri, 24 May 2019 00:59:23 -0700 X-Authentication-Warning: terminus.zytor.com: tipbot set sender to tipbot@zytor.com using -f From: tip-bot for Ingo Molnar Message-ID: Cc: mingo@kernel.org, brgerst@gmail.com, jgross@suse.com, hpa@zytor.com, peterz@infradead.org, bp@alien8.de, tglx@linutronix.de, dvlasenk@redhat.com, linux-kernel@vger.kernel.org, luto@kernel.org, torvalds@linux-foundation.org Reply-To: mingo@kernel.org, brgerst@gmail.com, jgross@suse.com, hpa@zytor.com, peterz@infradead.org, bp@alien8.de, tglx@linutronix.de, dvlasenk@redhat.com, linux-kernel@vger.kernel.org, luto@kernel.org, torvalds@linux-foundation.org In-Reply-To: <20190425095039.GC115378@gmail.com> References: <20190425095039.GC115378@gmail.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:x86/paravirt] x86/paravirt: Detect over-sized patching bugs in paravirt_patch_call() Git-Commit-ID: 11e86dc7f2746210f9c7dc10deaa7658f8dc8350 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 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 11e86dc7f2746210f9c7dc10deaa7658f8dc8350 Gitweb: https://git.kernel.org/tip/11e86dc7f2746210f9c7dc10deaa7658f8dc8350 Author: Ingo Molnar AuthorDate: Thu, 25 Apr 2019 11:50:39 +0200 Committer: Ingo Molnar CommitDate: Thu, 25 Apr 2019 12:00:44 +0200 x86/paravirt: Detect over-sized patching bugs in paravirt_patch_call() paravirt_patch_call() currently handles patching failures inconsistently: we generate a warning in the retpoline case, but don't in other cases where we might end up with a non-working kernel as well. So just convert it all to a BUG_ON(), these patching calls are *not* supposed to fail, and if they do we want to know it immediately. This also makes the kernel smaller and removes an #ifdef ugly. I tried it with a richly paravirt-enabled kernel and no patching bugs were detected. Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Juergen Gross Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/20190425095039.GC115378@gmail.com Signed-off-by: Ingo Molnar --- arch/x86/kernel/paravirt.c | 16 ++++++++-------- 1 file changed, 8 insertions(+), 8 deletions(-) diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c index 7f9121f2fdac..544d386ded45 100644 --- a/arch/x86/kernel/paravirt.c +++ b/arch/x86/kernel/paravirt.c @@ -73,21 +73,21 @@ struct branch { static unsigned paravirt_patch_call(void *insnbuf, const void *target, unsigned long addr, unsigned len) { + const int call_len = 5; struct branch *b = insnbuf; - unsigned long delta = (unsigned long)target - (addr+5); + unsigned long delta = (unsigned long)target - (addr+call_len); - if (len < 5) { -#ifdef CONFIG_RETPOLINE - WARN_ONCE(1, "Failing to patch indirect CALL in %ps\n", (void *)addr); -#endif - return len; /* call too long for patch site */ + if (len < call_len) { + pr_warn("paravirt: Failed to patch indirect CALL at %ps\n", (void *)addr); + /* Kernel might not be viable if patching fails, bail out: */ + BUG_ON(1); } b->opcode = 0xe8; /* call */ b->delta = delta; - BUILD_BUG_ON(sizeof(*b) != 5); + BUILD_BUG_ON(sizeof(*b) != call_len); - return 5; + return call_len; } #ifdef CONFIG_PARAVIRT_XXL