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 185CDC433EF for ; Wed, 4 May 2022 17:51:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1359654AbiEDRxf (ORCPT ); Wed, 4 May 2022 13:53:35 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55862 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1357929AbiEDRP1 (ORCPT ); Wed, 4 May 2022 13:15:27 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 92D8D56211; Wed, 4 May 2022 09:59:09 -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 dfw.source.kernel.org (Postfix) with ESMTPS id 59A9D6190E; Wed, 4 May 2022 16:59:09 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id AA1CEC385AA; Wed, 4 May 2022 16:59:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1651683548; bh=HmBIuhYSeuWE0pstQGhhP7R7GI28r+JeJNOKFNikFL4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=JzKYmye5gc1ud00CEzVo6OngZd5YH2rJ14E2ssOXvBSyi0LschbZheLiSAQ3o1FOd nOYv573nJtufMgRJmxsxYVmSm9GmTQgbN+CVG0UN5QMrY0PV1G4jM8P0RYFlajwDmE m7llCcz7/1ODOO5iTOROX3zfK3e4OtsDxUPXbo/0= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Daniel Starke Subject: [PATCH 5.17 202/225] tty: n_gsm: fix restart handling via CLD command Date: Wed, 4 May 2022 18:47:20 +0200 Message-Id: <20220504153128.173897412@linuxfoundation.org> X-Mailer: git-send-email 2.36.0 In-Reply-To: <20220504153110.096069935@linuxfoundation.org> References: <20220504153110.096069935@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Daniel Starke commit aa371e96f05dcb36a88298f5cb70aa7234d5e8b8 upstream. 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 5.8.2 states that both sides will revert to the non-multiplexed mode via a close-down message (CLD). The usual program flow is as following: - start multiplex mode by sending AT+CMUX to the mobile - establish the control channel (DLCI 0) - establish user channels (DLCI >0) - terminate user channels - send close-down message (CLD) - revert to AT protocol (i.e. leave multiplexed mode) The AT protocol is out of scope of the n_gsm driver. However, gsm_disconnect() sends CLD if gsm_config() detects that the requested parameters require the mux protocol to restart. The next immediate action is to start the mux protocol by opening DLCI 0 again. Any responder side which handles CLD commands correctly forces us to fail at this point because AT+CMUX needs to be sent to the mobile to start the mux again. Therefore, remove the CLD command in this phase and keep both sides in multiplexed mode. Remove the gsm_disconnect() function as it become unnecessary and merge the remaining parts into gsm_cleanup_mux() to handle the termination order and locking correctly. Fixes: 71e077915396 ("tty: n_gsm: do not send/receive in ldisc close path") Cc: stable@vger.kernel.org Signed-off-by: Daniel Starke Link: https://lore.kernel.org/r/20220414094225.4527-2-daniel.starke@siemens.com Signed-off-by: Greg Kroah-Hartman --- drivers/tty/n_gsm.c | 68 +++++++++++++++------------------------------------- 1 file changed, 20 insertions(+), 48 deletions(-) --- a/drivers/tty/n_gsm.c +++ b/drivers/tty/n_gsm.c @@ -2106,49 +2106,35 @@ static void gsm_error(struct gsm_mux *gs gsm->io_error++; } -static int gsm_disconnect(struct gsm_mux *gsm) -{ - struct gsm_dlci *dlci = gsm->dlci[0]; - struct gsm_control *gc; - - if (!dlci) - return 0; - - /* In theory disconnecting DLCI 0 is sufficient but for some - modems this is apparently not the case. */ - gc = gsm_control_send(gsm, CMD_CLD, NULL, 0); - if (gc) - gsm_control_wait(gsm, gc); - - del_timer_sync(&gsm->t2_timer); - /* Now we are sure T2 has stopped */ - - gsm_dlci_begin_close(dlci); - wait_event_interruptible(gsm->event, - dlci->state == DLCI_CLOSED); - - if (signal_pending(current)) - return -EINTR; - - return 0; -} - /** * gsm_cleanup_mux - generic GSM protocol cleanup * @gsm: our mux + * @disc: disconnect link? * * Clean up the bits of the mux which are the same for all framing * protocols. Remove the mux from the mux table, stop all the timers * and then shut down each device hanging up the channels as we go. */ -static void gsm_cleanup_mux(struct gsm_mux *gsm) +static void gsm_cleanup_mux(struct gsm_mux *gsm, bool disc) { int i; struct gsm_dlci *dlci = gsm->dlci[0]; struct gsm_msg *txq, *ntxq; gsm->dead = true; + mutex_lock(&gsm->mutex); + + if (dlci) { + if (disc && dlci->state != DLCI_CLOSED) { + gsm_dlci_begin_close(dlci); + wait_event(gsm->event, dlci->state == DLCI_CLOSED); + } + dlci->dead = true; + } + + /* Finish outstanding timers, making sure they are done */ + del_timer_sync(&gsm->t2_timer); spin_lock(&gsm_mux_lock); for (i = 0; i < MAX_MUX; i++) { @@ -2162,13 +2148,7 @@ static void gsm_cleanup_mux(struct gsm_m if (i == MAX_MUX) return; - del_timer_sync(&gsm->t2_timer); - /* Now we are sure T2 has stopped */ - if (dlci) - dlci->dead = true; - /* Free up any link layer users */ - mutex_lock(&gsm->mutex); for (i = 0; i < NUM_DLCI; i++) if (gsm->dlci[i]) gsm_dlci_release(gsm->dlci[i]); @@ -2370,19 +2350,11 @@ static int gsm_config(struct gsm_mux *gs /* * Close down what is needed, restart and initiate the new - * configuration + * configuration. On the first time there is no DLCI[0] + * and closing or cleaning up is not necessary. */ - - if (need_close || need_restart) { - int ret; - - ret = gsm_disconnect(gsm); - - if (ret) - return ret; - } - if (need_restart) - gsm_cleanup_mux(gsm); + if (need_close || need_restart) + gsm_cleanup_mux(gsm, true); gsm->initiator = c->initiator; gsm->mru = c->mru; @@ -2494,7 +2466,7 @@ static void gsmld_detach_gsm(struct tty_ for (i = 1; i < NUM_DLCI; i++) tty_unregister_device(gsm_tty_driver, base + i); } - gsm_cleanup_mux(gsm); + gsm_cleanup_mux(gsm, false); tty_kref_put(gsm->tty); gsm->tty = NULL; } @@ -2597,7 +2569,7 @@ static int gsmld_open(struct tty_struct ret = gsmld_attach_gsm(tty, gsm); if (ret != 0) { - gsm_cleanup_mux(gsm); + gsm_cleanup_mux(gsm, false); mux_put(gsm); } return ret;