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 5CDBFCCA487 for ; Mon, 13 Jun 2022 11:09:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1352137AbiFMLJZ (ORCPT ); Mon, 13 Jun 2022 07:09:25 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45184 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1351764AbiFMLE7 (ORCPT ); Mon, 13 Jun 2022 07:04:59 -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 C5FD327CC5; Mon, 13 Jun 2022 03:33:58 -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 6AD1BB80E94; Mon, 13 Jun 2022 10:33:58 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id C27FBC34114; Mon, 13 Jun 2022 10:33:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1655116437; bh=902gFoAgWWQFr8ZEXLjOR7pDD0ubzAz8YbNtrMgiSvY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=NMDGzP7m3kzHAmY7/QAAi1X61HIKMdz+PlpcYvw3ZE/7h3nOTaSTMssZFzyhveazS kUgwQJ4zYp1d8PFsU+Neqk0BSzp9thuqrkAKJfKIEs5ZjysNfDDesbSviLdJbcWtn5 B3jSMvDnatwX1/N4xN1jPipxdw7cQ0UAhPfcihik= 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 5.4 086/411] x86/delay: Fix the wrong asm constraint in delay_loop() Date: Mon, 13 Jun 2022 12:05:59 +0200 Message-Id: <20220613094931.259536438@linuxfoundation.org> X-Mailer: git-send-email 2.36.1 In-Reply-To: <20220613094928.482772422@linuxfoundation.org> References: <20220613094928.482772422@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 c126571e5e2e..3d1cfad36ba2 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