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 AF308C433F5 for ; Thu, 19 May 2022 16:17:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241906AbiESQRm (ORCPT ); Thu, 19 May 2022 12:17:42 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43998 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232987AbiESQRd (ORCPT ); Thu, 19 May 2022 12:17:33 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D5F03D0289; Thu, 19 May 2022 09:17:31 -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 8F899B8266C; Thu, 19 May 2022 16:17:30 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id D80B3C385AA; Thu, 19 May 2022 16:17:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1652977049; bh=U5yzL+CNoWVKrDgGlCP/DCVT+PIEOgDIgx3wiuOFGFM=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=LmkJc7DkBLA8Qi9GHuf+MM9b5EhJ2jIlhirBdaKWAyiWrfYywDdkgNDbMbJdlH4cb 6g0LYLYPPm9WepowDFrdWTv3R/CdQXr4z3T+08Bj0z5rRSbYuqqSAOoHx1bhUwC6r9 mirodZrKFOp3SITLWSeMwy1i3bYddIHct0nJo2Qw= Date: Thu, 19 May 2022 18:17:26 +0200 From: Greg KH To: "D. Starke" Cc: linux-serial@vger.kernel.org, jirislaby@kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 1/9] tty: n_gsm: fix user open not possible at responder until initiator open Message-ID: References: <20220519070757.2096-1-daniel.starke@siemens.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220519070757.2096-1-daniel.starke@siemens.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, May 19, 2022 at 09:07:49AM +0200, D. Starke wrote: > From: Daniel Starke > > After setting up the control channel on both sides the responder side may > want to open a virtual tty to listen on until the initiator starts an > application on a user channel. The current implementation allows the > open() but no other operation, like termios. These fail with EINVAL. > The responder sided application has no means to detect an open by the > initiator sided application this way. And the initiator sided applications > usually expect the responder sided application to listen on the user > channel upon open. > Set the user channel into half-open state on responder side once a user > application opens the virtual tty to allow IO operations on it. > Furthermore, keep the user channel constipated until the initiator side > opens it to give the responder sided application the chance to detect the > new connection and to avoid data loss if the responder sided application > starts sending before the user channel is open. > > Fixes: e1eaea46bb40 ("tty: n_gsm line discipline") > Cc: stable@vger.kernel.org > Signed-off-by: Daniel Starke > --- > drivers/tty/n_gsm.c | 31 +++++++++++++++++++++++++++++-- > 1 file changed, 29 insertions(+), 2 deletions(-) > > This commit was not changed as there have been no comments on it in v1. > > Link: https://lore.kernel.org/all/20220506144725.1946-1-daniel.starke@siemens.com/ > > diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c > index fd8b86dde525..08fea3e7674d 100644 > --- a/drivers/tty/n_gsm.c > +++ b/drivers/tty/n_gsm.c > @@ -1493,6 +1493,8 @@ static void gsm_dlci_close(struct gsm_dlci *dlci) > if (debug & 8) > pr_debug("DLCI %d goes closed.\n", dlci->addr); > dlci->state = DLCI_CLOSED; > + /* Prevent us from sending data before the link is up again */ > + dlci->constipated = true; > if (dlci->addr != 0) { > tty_port_tty_hangup(&dlci->port, false); > spin_lock_irqsave(&dlci->lock, flags); > @@ -1522,6 +1524,7 @@ static void gsm_dlci_open(struct gsm_dlci *dlci) > del_timer(&dlci->t1); > /* This will let a tty open continue */ > dlci->state = DLCI_OPEN; > + dlci->constipated = false; > if (debug & 8) > pr_debug("DLCI %d goes open.\n", dlci->addr); > /* Send current modem state */ > @@ -1602,6 +1605,25 @@ static void gsm_dlci_begin_open(struct gsm_dlci *dlci) > mod_timer(&dlci->t1, jiffies + gsm->t1 * HZ / 100); > } > > +/** > + * gsm_dlci_wait_open - wait for channel open procedure > + * @dlci: DLCI to open > + * > + * Wait for a DLCI opening from the other side. Asynchronously wait until > + * we get a SABM and set off timers and the responses. > + */ > +static void gsm_dlci_wait_open(struct gsm_dlci *dlci) > +{ > + switch (dlci->state) { > + case DLCI_CLOSED: > + case DLCI_CLOSING: > + dlci->state = DLCI_OPENING; > + break; > + default: > + break; > + } > +} The documentation for this function is odd, you are not waiting for anything. You are just changing the state. This makes no sense as-is, sorry. greg k-h