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=-13.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 A5093C433ED for ; Thu, 22 Apr 2021 16:21:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 714FB61405 for ; Thu, 22 Apr 2021 16:21:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236616AbhDVQWY convert rfc822-to-8bit (ORCPT ); Thu, 22 Apr 2021 12:22:24 -0400 Received: from eu-smtp-delivery-151.mimecast.com ([185.58.85.151]:47292 "EHLO eu-smtp-delivery-151.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236236AbhDVQWT (ORCPT ); Thu, 22 Apr 2021 12:22:19 -0400 Received: from AcuMS.aculab.com (156.67.243.121 [156.67.243.121]) (Using TLS) by relay.mimecast.com with ESMTP id uk-mta-270-mhKvP-dDOsuLyQ0QyQj3_Q-1; Thu, 22 Apr 2021 17:21:41 +0100 X-MC-Unique: mhKvP-dDOsuLyQ0QyQj3_Q-1 Received: from AcuMS.Aculab.com (fd9f:af1c:a25b:0:994c:f5c2:35d6:9b65) by AcuMS.aculab.com (fd9f:af1c:a25b:0:994c:f5c2:35d6:9b65) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Thu, 22 Apr 2021 17:21:40 +0100 Received: from AcuMS.Aculab.com ([fe80::994c:f5c2:35d6:9b65]) by AcuMS.aculab.com ([fe80::994c:f5c2:35d6:9b65%12]) with mapi id 15.00.1497.015; Thu, 22 Apr 2021 17:21:40 +0100 From: David Laight To: 'Dan Carpenter' , Joel Stanley CC: 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" Subject: RE: [PATCH] soc: aspeed: fix a ternary sign expansion bug Thread-Topic: [PATCH] soc: aspeed: fix a ternary sign expansion bug Thread-Index: AQHXN1ec+IlNNgnl7EGootyN/jCOrarAtu4w Date: Thu, 22 Apr 2021 16:21:40 +0000 Message-ID: <59596244622c4a15ac8cc0747332d0be@AcuMS.aculab.com> References: In-Reply-To: Accept-Language: en-GB, en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.107] MIME-Version: 1.0 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=C51A453 smtp.mailfrom=david.laight@aculab.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: aculab.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 much prefer adding 0 to a cast to fix integer types. In can go less wrong! IMHO there are far too many casts in the kernel sources. Especially the ones that are only there to appease sparse. A functional notation for those would remove some of the potential problems. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)