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 29B11C433F5 for ; Thu, 19 May 2022 07:10:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229598AbiESHKa (ORCPT ); Thu, 19 May 2022 03:10:30 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39272 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234540AbiESHJ0 (ORCPT ); Thu, 19 May 2022 03:09:26 -0400 Received: from mta-65-225.siemens.flowmailer.net (mta-65-225.siemens.flowmailer.net [185.136.65.225]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 987D1BA541 for ; Thu, 19 May 2022 00:09:24 -0700 (PDT) Received: by mta-65-225.siemens.flowmailer.net with ESMTPSA id 20220519070924e22288415dd2e655ba for ; Thu, 19 May 2022 09:09:24 +0200 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; s=fm1; d=siemens.com; i=daniel.starke@siemens.com; h=Date:From:Subject:To:Message-ID:MIME-Version:Content-Type:Content-Transfer-Encoding:Cc:References:In-Reply-To; bh=nqoNi8RvH8jFm/9BUGmPRREecUmmOw+Z6oka13L341g=; b=c2x674HTjv0Jcr6ksQjsNaHxn1qdXMlvDirbRsxrQfYaBomRKa01KkrPyuSiSjiwPzUHm/ hhhm+OabeG3YliIA6MANSsHYnIzaBFfbKN1rw2X/evccG6vxd7jDYyPw2yDGzQVDxvvnfGJm adIdZ7OicIkSabjSi8pJQmbRi0OeU=; From: "D. Starke" To: linux-serial@vger.kernel.org, gregkh@linuxfoundation.org, jirislaby@kernel.org Cc: linux-kernel@vger.kernel.org, Daniel Starke Subject: [PATCH v2 9/9] tty: n_gsm: fix race condition in gsmld_write() Date: Thu, 19 May 2022 09:07:57 +0200 Message-Id: <20220519070757.2096-9-daniel.starke@siemens.com> In-Reply-To: <20220519070757.2096-1-daniel.starke@siemens.com> References: <20220519070757.2096-1-daniel.starke@siemens.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Flowmailer-Platform: Siemens Feedback-ID: 519:519-314044:519-21489:flowmailer Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Daniel Starke The function may be used by the user directly and also by the n_gsm internal functions. They can lead into a race condition which results in interleaved frames if both are writing at the same time. The receiving side is not able to decode those interleaved frames correctly. Add a lock around the low side tty write to avoid race conditions and frame interleaving between user originated writes and n_gsm writes. Fixes: e1eaea46bb40 ("tty: n_gsm line discipline") Cc: stable@vger.kernel.org Signed-off-by: Daniel Starke --- drivers/tty/n_gsm.c | 21 +++++++++++++++++---- 1 file changed, 17 insertions(+), 4 deletions(-) See patch 6 regarding changes since to v1. diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c index cc349f5a37fb..640c0f0aa7b1 100644 --- a/drivers/tty/n_gsm.c +++ b/drivers/tty/n_gsm.c @@ -2999,11 +2999,24 @@ static ssize_t gsmld_read(struct tty_struct *tty, struct file *file, static ssize_t gsmld_write(struct tty_struct *tty, struct file *file, const unsigned char *buf, size_t nr) { - int space = tty_write_room(tty); + struct gsm_mux *gsm = tty->disc_data; + unsigned long flags; + int space; + int ret; + + if (!gsm) + return -ENODEV; + + ret = -ENOBUFS; + spin_lock_irqsave(&gsm->tx_lock, flags); + space = tty_write_room(tty); if (space >= nr) - return tty->ops->write(tty, buf, nr); - set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags); - return -ENOBUFS; + ret = tty->ops->write(tty, buf, nr); + else + set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags); + spin_unlock_irqrestore(&gsm->tx_lock, flags); + + return ret; } /** -- 2.34.1