From patchwork Mon Feb 28 17:25:07 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 547066 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 7BE43C43219 for ; Mon, 28 Feb 2022 17:55:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239272AbiB1Rzw (ORCPT ); Mon, 28 Feb 2022 12:55:52 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51172 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240599AbiB1RyZ (ORCPT ); Mon, 28 Feb 2022 12:54:25 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2E03998F46; Mon, 28 Feb 2022 09:42:34 -0800 (PST) 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 ABD18B815B3; Mon, 28 Feb 2022 17:42:32 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0EE97C340E7; Mon, 28 Feb 2022 17:42:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1646070151; bh=leDzcSYyD19gQUJdRqvf6Ehk5Ueop+kOP2W9my9OZK8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=QUfY/H/7WBlVfGbjZM4Q1Nx7BZa9TkyFoOhP3fGswn5McrtE3kWYnLIvXLoow9P+p Hkqw56HZGD8Zi8iX5NdWOzUsqDiTLjLQA3k+NYUGRFjhfZXmzk+exkET9ZPEahmAoG gdSISfAkw5XZj81HMLHsERJ5HK7p/YjRq6UuwrNA= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Daniel Starke Subject: [PATCH 5.15 133/139] tty: n_gsm: fix deadlock in gsmtty_open() Date: Mon, 28 Feb 2022 18:25:07 +0100 Message-Id: <20220228172401.655465894@linuxfoundation.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220228172347.614588246@linuxfoundation.org> References: <20220228172347.614588246@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: daniel.starke@siemens.com commit a2ab75b8e76e455af7867e3835fd9cdf386b508f upstream. In the current implementation the user may open a virtual tty which then could fail to establish the underlying DLCI. The function gsmtty_open() gets stuck in tty_port_block_til_ready() while waiting for a carrier rise. This happens if the remote side fails to acknowledge the link establishment request in time or completely. At some point gsm_dlci_close() is called to abort the link establishment attempt. The function tries to inform the associated virtual tty by performing a hangup. But the blocking loop within tty_port_block_til_ready() is not informed about this event. The patch proposed here fixes this by resetting the initialization state of the virtual tty to ensure the loop exits and triggering it to make tty_port_block_til_ready() return. Fixes: e1eaea46bb40 ("tty: n_gsm line discipline") Cc: stable@vger.kernel.org Signed-off-by: Daniel Starke Link: https://lore.kernel.org/r/20220218073123.2121-7-daniel.starke@siemens.com Signed-off-by: Greg Kroah-Hartman --- drivers/tty/n_gsm.c | 3 +++ 1 file changed, 3 insertions(+) --- a/drivers/tty/n_gsm.c +++ b/drivers/tty/n_gsm.c @@ -1431,6 +1431,9 @@ static void gsm_dlci_close(struct gsm_dl if (dlci->addr != 0) { tty_port_tty_hangup(&dlci->port, false); kfifo_reset(&dlci->fifo); + /* Ensure that gsmtty_open() can return. */ + tty_port_set_initialized(&dlci->port, 0); + wake_up_interruptible(&dlci->port.open_wait); } else dlci->gsm->dead = true; wake_up(&dlci->gsm->event);