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 000A3C2BA4C for ; Wed, 26 Jan 2022 13:52:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234796AbiAZNwW (ORCPT ); Wed, 26 Jan 2022 08:52:22 -0500 Received: from ams.source.kernel.org ([145.40.68.75]:32884 "EHLO ams.source.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241646AbiAZNwU (ORCPT ); Wed, 26 Jan 2022 08:52:20 -0500 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 73D4CB80AAD; Wed, 26 Jan 2022 13:52:19 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id DE873C340E3; Wed, 26 Jan 2022 13:52:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1643205138; bh=uSJ0ZOYPJyZVA9tbsTEE513frvV72L1M7icrS+I9sCE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=jUnY4yyhJOcYsw/W5FB8+xAOimFoR4ygkcucYYqX49TyQUAHBvSUPzjuoiXk+LHt+ gBUc3ZdfFA1Ex40FmjJP8sGfgHuIgAIzFeLr6N0r/YKD7InsK/DkDuV12rH8hyWj/G B+YL6RMbt2a3de9S8nFQtuIdQe7LZ4t2j2WB0whY= Date: Wed, 26 Jan 2022 14:52:15 +0100 From: Greg KH To: daniel.starke@siemens.com Cc: linux-serial@vger.kernel.org, jirislaby@kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH v2 1/1] tty: n_gsm: fix SW flow control encoding/handling Message-ID: References: <20220120101857.2509-1-daniel.starke@siemens.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220120101857.2509-1-daniel.starke@siemens.com> Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On Thu, Jan 20, 2022 at 02:18:57AM -0800, daniel.starke@siemens.com wrote: > n_gsm is based on the 3GPP 07.010 and its newer version is the 3GPP 27.010. > See https://portal.3gpp.org/desktopmodules/Specifications/SpecificationDetails.aspx?specificationId=1516 > The changes from 07.010 to 27.010 are non-functional. Therefore, I refer to > the newer 27.010 here. Chapter 5.2.7.3 states that DC1 (XON) and DC3 (XOFF) > are the control characters defined in ISO/IEC 646. These shall be quoted if > seen in the data stream to avoid interpretation as flow control characters. > > ISO/IEC 646 refers to the set of ISO standards described as the ISO > 7-bit coded character set for information interchange. Its final version > is also known as ITU T.50. > See https://www.itu.int/rec/T-REC-T.50-199209-I/en > > To abide the standard it is needed to quote DC1 and DC3 correctly if these > are seen as data bytes and not as control characters. The current > implementation already tries to enforce this but fails to catch all > defined cases. 3GPP 27.010 chapter 5.2.7.3 clearly states that the most > significant bit shall be ignored for DC1 and DC3 handling. The current > implementation handles only the case with the most significant bit set 0. > Cases in which DC1 and DC3 have the most significant bit set 1 are left > unhandled. > > This patch fixes this by masking the data bytes with ISO_IEC_646_MASK (only > the 7 least significant bits set 1) before comparing them with XON > (a.k.a. DC1) and XOFF (a.k.a. DC3) when testing which byte values need > quotation via byte stuffing. > > Fixes: e1eaea46bb40 (tty: n_gsm line discipline, 2010-03-26) Nit, no need for a date here, our tools get mad about stuff like this. Look at the proper format for "Fixes:" line in the documentation. thanks, greg k-h