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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 40ECACCA47C for ; Mon, 13 Jun 2022 11:49:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1355576AbiFMLto (ORCPT ); Mon, 13 Jun 2022 07:49:44 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41660 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1357579AbiFMLqY (ORCPT ); Mon, 13 Jun 2022 07:46:24 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7B97D26103; Mon, 13 Jun 2022 03:52:52 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 81AEDB80E93; Mon, 13 Jun 2022 10:52:50 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id CCC6FC34114; Mon, 13 Jun 2022 10:52:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1655117569; bh=8YH6x0Tqyp6rJkWOfjcRIC8Y6lDqvyPZclzyU51XQPY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=rysj93qJET1Pb9U3VUuDsCpyODl88gbeKjgKV00zyaFiRn9yKGn+A3R1aulDdPlkI 13mG7y1w+q4qdLFzP6Nxl+uzhZbJ1u1OxwcZPR3bZCOJtq+ahtJ1pFZbL6pse1alKm kdmWrpRvtow6leceEAufXWF04w95+ZRgtukh+mgw= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Ammar Faizi , Borislav Petkov , Sasha Levin Subject: [PATCH 4.19 063/287] x86/delay: Fix the wrong asm constraint in delay_loop() Date: Mon, 13 Jun 2022 12:08:07 +0200 Message-Id: <20220613094925.781139943@linuxfoundation.org> X-Mailer: git-send-email 2.36.1 In-Reply-To: <20220613094923.832156175@linuxfoundation.org> References: <20220613094923.832156175@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Ammar Faizi [ Upstream commit b86eb74098a92afd789da02699b4b0dd3f73b889 ] The asm constraint does not reflect the fact that the asm statement can modify the value of the local variable loops. Which it does. Specifying the wrong constraint may lead to undefined behavior, it may clobber random stuff (e.g. local variable, important temporary value in regs, etc.). This is especially dangerous when the compiler decides to inline the function and since it doesn't know that the value gets modified, it might decide to use it from a register directly without reloading it. Change the constraint to "+a" to denote that the first argument is an input and an output argument. [ bp: Fix typo, massage commit message. ] Fixes: e01b70ef3eb3 ("x86: fix bug in arch/i386/lib/delay.c file, delay_loop function") Signed-off-by: Ammar Faizi Signed-off-by: Borislav Petkov Link: https://lore.kernel.org/r/20220329104705.65256-2-ammarfaizi2@gnuweeb.org Signed-off-by: Sasha Levin --- arch/x86/lib/delay.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/x86/lib/delay.c b/arch/x86/lib/delay.c index 614c2c6b1959..68ca883abfdb 100644 --- a/arch/x86/lib/delay.c +++ b/arch/x86/lib/delay.c @@ -43,8 +43,8 @@ static void delay_loop(unsigned long loops) " jnz 2b \n" "3: dec %0 \n" - : /* we don't need output */ - :"a" (loops) + : "+a" (loops) + : ); } -- 2.35.1