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 1CEBAC433EF for ; Mon, 13 Jun 2022 10:18:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242063AbiFMKSA (ORCPT ); Mon, 13 Jun 2022 06:18:00 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57734 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241683AbiFMKRc (ORCPT ); Mon, 13 Jun 2022 06:17:32 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 88EAC1FCED; Mon, 13 Jun 2022 03:15:39 -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 0B855B80E92; Mon, 13 Jun 2022 10:15:34 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 76300C34114; Mon, 13 Jun 2022 10:15:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1655115332; bh=9fM207ThNnSdzxF2rwXN/zW9jb0LrWT0dcV66EEyAQs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=gMO3ne67dtM+co9vdgi1kzjYaReMj4EMdfiN4pAoBikkmmO+vmg6GwLpnN2BSSDrJ uMpAHignzsb4Nv7N2rSVNf6WjuOsYItVd+mbFcnQ6tcEB4E+IbcBOlLDbEyJT4OpYa Sijg8WOEOv5VU6wqHObmL+7K0opGjrL0G6X2mBk0= 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 4.9 038/167] x86/delay: Fix the wrong asm constraint in delay_loop() Date: Mon, 13 Jun 2022 12:08:32 +0200 Message-Id: <20220613094849.810646269@linuxfoundation.org> X-Mailer: git-send-email 2.36.1 In-Reply-To: <20220613094840.720778945@linuxfoundation.org> References: <20220613094840.720778945@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: linux-kernel@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 71a3759a2d4e..60cc4f222cbf 100644 --- a/arch/x86/lib/delay.c +++ b/arch/x86/lib/delay.c @@ -42,8 +42,8 @@ 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