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=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,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 98C0FC43461 for ; Fri, 23 Apr 2021 00:07:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6004861008 for ; Fri, 23 Apr 2021 00:07:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240068AbhDWAHz (ORCPT ); Thu, 22 Apr 2021 20:07:55 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51042 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240041AbhDWAHx (ORCPT ); Thu, 22 Apr 2021 20:07:53 -0400 Received: from mail-qv1-xf30.google.com (mail-qv1-xf30.google.com [IPv6:2607:f8b0:4864:20::f30]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A4DCBC06174A; Thu, 22 Apr 2021 17:07:17 -0700 (PDT) Received: by mail-qv1-xf30.google.com with SMTP id dp18so18372366qvb.5; Thu, 22 Apr 2021 17:07:17 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=jms.id.au; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=JfM3d7LOiLS9qmGDziTRg1PSfPwhJZSu7g8WxAmeWYU=; b=CPLFUXiNh4B93n9Xa5TPQoafBuJO+Xzvo6rwK5wfYF3Lpx9T05KuYCVSKj9fJcrIJG QwBAnHWwPqlV2hBpDeOEawH0udkeNH6RtSJb4e89xjKokYFgoFRYLVkoio1Rg52snfp0 3b2R+eu7uryyY++tta636sg60TtoVc1+IKtRw= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=JfM3d7LOiLS9qmGDziTRg1PSfPwhJZSu7g8WxAmeWYU=; b=DnL8qseHJ68Mc8GZktbMoV0eoY5PURw0cH8/1simvNWvHe78O/v5D2nJUEalU/LEJ/ Ki5g3wAAoHRnryi1KN0/gI78x6hQbYRpLBSK2cBQXvij7SLS6rg05xJQKuU4YTe3/Ale ZoPpGB/KqOH6zm6qjQOvgF15W+RTdvsIpALgd6TF+LWuqqoD7AkUJc/WrAnY+WVB2V/G VfIk2fd7mZIHwf5TXhQtDvVw1XGeYwJncPfBO3Xs9Jdr4pFz/Nnn3xQ2pxXFeUnfq/XO RboAPqrbyHDJjFxTWNw98cwpRClRogEv0+Ib4XD3jp1kUFkVZ9DX84qHQpo5yNW1n/jG QcmQ== X-Gm-Message-State: AOAM531SiH2IwyfWtMaNX+WP5ntCaLeI+OorWAK2YX8MnibdgS2nDuui MQRaIilUepUM0SOx14jcpC4VDM8OeJtY6IzEHkQ= X-Google-Smtp-Source: ABdhPJwzrmIHJN3KSKdUfPi114SsARBXFjKZOnUsANQ2c4AII3cxjV1HF1foJ0rKi1mBguFhLOW4GX9GnFoT5okPR5s= X-Received: by 2002:a0c:eb06:: with SMTP id j6mr1253747qvp.10.1619136436827; Thu, 22 Apr 2021 17:07:16 -0700 (PDT) MIME-Version: 1.0 References: <59596244622c4a15ac8cc0747332d0be@AcuMS.aculab.com> In-Reply-To: <59596244622c4a15ac8cc0747332d0be@AcuMS.aculab.com> From: Joel Stanley Date: Fri, 23 Apr 2021 00:07:04 +0000 Message-ID: Subject: Re: [PATCH] soc: aspeed: fix a ternary sign expansion bug To: David Laight Cc: Dan Carpenter , Andrew Jeffery , "Chia-Wei, Wang" , Jae Hyun Yoo , John Wang , Brad Bishop , Patrick Venture , Benjamin Fair , Greg Kroah-Hartman , Robert Lippert , "linux-aspeed@lists.ozlabs.org" , "linux-kernel@vger.kernel.org" , "kernel-janitors@vger.kernel.org" Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 22 Apr 2021 at 16:21, David Laight wrote: > > From: Dan Carpenter > > Sent: 22 April 2021 10:12 > > > > The intent here was to return negative error codes but it actually > > returns positive values. The problem is that type promotion with > > ternary operations is quite complicated. > > > > "ret" is an int. "copied" is a u32. And the snoop_file_read() function > > returns long. What happens is that "ret" is cast to u32 and becomes > > positive then it's cast to long and it's still positive. > > > > Fix this by removing the ternary so that "ret" is type promoted directly > > to long. > > > > Fixes: 3772e5da4454 ("drivers/misc: Aspeed LPC snoop output using misc chardev") > > Signed-off-by: Dan Carpenter > > --- > > drivers/soc/aspeed/aspeed-lpc-snoop.c | 4 +++- > > 1 file changed, 3 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/soc/aspeed/aspeed-lpc-snoop.c b/drivers/soc/aspeed/aspeed-lpc-snoop.c > > index 210455efb321..eceeaf8dfbeb 100644 > > --- a/drivers/soc/aspeed/aspeed-lpc-snoop.c > > +++ b/drivers/soc/aspeed/aspeed-lpc-snoop.c > > @@ -94,8 +94,10 @@ static ssize_t snoop_file_read(struct file *file, char __user *buffer, > > return -EINTR; > > } > > ret = kfifo_to_user(&chan->fifo, buffer, count, &copied); > > + if (ret) > > + return ret; > > > > - return ret ? ret : copied; > > + return copied; > > I wonder if changing it to: > return ret ? ret + 0L : copied; > > Might make people think in the future and not convert it back > as an 'optimisation'. I think the change that Dan posted is clear. Thanks Dan! I'll get it queued up. Cheers, Joel