From nobody Sun Dec 14 08:04:12 2025 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 09A2CC00140 for ; Mon, 15 Aug 2022 19:34:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233119AbiHOTeP (ORCPT ); Mon, 15 Aug 2022 15:34:15 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37306 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1345012AbiHOT1g (ORCPT ); Mon, 15 Aug 2022 15:27:36 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E08405B7BB; Mon, 15 Aug 2022 11:43:27 -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 4E7BDB810A1; Mon, 15 Aug 2022 18:43:26 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A7B91C433D7; Mon, 15 Aug 2022 18:43:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1660589005; bh=zn8xdHTvk6cuJwKCSSmY3TtG/YeiFQm5hr60CWdFPHE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=s7cYMpN7gBW0ieJ+1vFETmF9JwOv+FhGYTxFQZTmE4ahPzGbYcFxatlel9uaR4xdl EEspreW4e2B6VMsthf7bdAKqCCXdNuzHrkER5d1SZ+jIgbZPSmKaMN6iiQx9xqBh8a I8IbBxMt4MVUsYNTamfaWnaoKoUkB6MSNMlGoVSs= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Daniel Starke , Sasha Levin Subject: [PATCH 5.15 583/779] tty: n_gsm: fix user open not possible at responder until initiator open Date: Mon, 15 Aug 2022 20:03:47 +0200 Message-Id: <20220815180402.254233998@linuxfoundation.org> X-Mailer: git-send-email 2.37.2 In-Reply-To: <20220815180337.130757997@linuxfoundation.org> References: <20220815180337.130757997@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" From: Daniel Starke [ Upstream commit ac77f0077c3265197d378158c85a55eee6d21508 ] 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") Signed-off-by: Daniel Starke Link: https://lore.kernel.org/r/20220701061652.39604-1-daniel.starke@siemen= s.com Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin --- drivers/tty/n_gsm.c | 31 +++++++++++++++++++++++++++++-- 1 file changed, 29 insertions(+), 2 deletions(-) diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c index f86c5ebfcf91..36d5afa25fbb 100644 --- a/drivers/tty/n_gsm.c +++ b/drivers/tty/n_gsm.c @@ -1524,6 +1524,8 @@ static void gsm_dlci_close(struct gsm_dlci *dlci) if (debug & 8) pr_debug("DLCI %d goes closed.\n", dlci->addr); dlci->state =3D DLCI_CLOSED; + /* Prevent us from sending data before the link is up again */ + dlci->constipated =3D true; if (dlci->addr !=3D 0) { tty_port_tty_hangup(&dlci->port, false); spin_lock_irqsave(&dlci->lock, flags); @@ -1553,6 +1555,7 @@ static void gsm_dlci_open(struct gsm_dlci *dlci) del_timer(&dlci->t1); /* This will let a tty open continue */ dlci->state =3D DLCI_OPEN; + dlci->constipated =3D false; if (debug & 8) pr_debug("DLCI %d goes open.\n", dlci->addr); /* Send current modem state */ @@ -1633,6 +1636,25 @@ static void gsm_dlci_begin_open(struct gsm_dlci *dlc= i) mod_timer(&dlci->t1, jiffies + gsm->t1 * HZ / 100); } =20 +/** + * gsm_dlci_set_opening - change state to opening + * @dlci: DLCI to open + * + * Change internal state to wait for DLCI open from initiator side. + * We set off timers and responses upon reception of an SABM. + */ +static void gsm_dlci_set_opening(struct gsm_dlci *dlci) +{ + switch (dlci->state) { + case DLCI_CLOSED: + case DLCI_CLOSING: + dlci->state =3D DLCI_OPENING; + break; + default: + break; + } +} + /** * gsm_dlci_begin_close - start channel open procedure * @dlci: DLCI to open @@ -1776,10 +1798,13 @@ static struct gsm_dlci *gsm_dlci_alloc(struct gsm_m= ux *gsm, int addr) dlci->addr =3D addr; dlci->adaption =3D gsm->adaption; dlci->state =3D DLCI_CLOSED; - if (addr) + if (addr) { dlci->data =3D gsm_dlci_data; - else + /* Prevent us from sending data before the link is up */ + dlci->constipated =3D true; + } else { dlci->data =3D gsm_dlci_command; + } gsm->dlci[addr] =3D dlci; return dlci; } @@ -3226,6 +3251,8 @@ static int gsmtty_open(struct tty_struct *tty, struct= file *filp) /* Start sending off SABM messages */ if (gsm->initiator) gsm_dlci_begin_open(dlci); + else + gsm_dlci_set_opening(dlci); /* And wait for virtual carrier */ return tty_port_block_til_ready(port, tty, filp); } --=20 2.35.1