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 X-Spam-Level: X-Spam-Status: No, score=-16.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 65E46C1B0E3 for ; Thu, 10 Dec 2020 18:54:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 39D7B23D56 for ; Thu, 10 Dec 2020 18:54:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2393172AbgLJSvA (ORCPT ); Thu, 10 Dec 2020 13:51:00 -0500 Received: from mail.kernel.org ([198.145.29.99]:39508 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389254AbgLJOb6 (ORCPT ); Thu, 10 Dec 2020 09:31:58 -0500 From: Greg Kroah-Hartman Authentication-Results: mail.kernel.org; dkim=permerror (bad message/signature format) To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Shisong Qin , Samuel Thibault Subject: [PATCH 4.14 21/31] speakup: Reject setting the speakup line discipline outside of speakup Date: Thu, 10 Dec 2020 15:26:58 +0100 Message-Id: <20201210142603.152343956@linuxfoundation.org> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20201210142602.099683598@linuxfoundation.org> References: <20201210142602.099683598@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: Samuel Thibault commit f0992098cadb4c9c6a00703b66cafe604e178fea upstream. Speakup exposing a line discipline allows userland to try to use it, while it is deemed to be useless, and thus uselessly exposes potential bugs. One of them is simply that in such a case if the line sends data, spk_ttyio_receive_buf2 is called and crashes since spk_ttyio_synth is NULL. This change restricts the use of the speakup line discipline to speakup drivers, thus avoiding such kind of issues altogether. Cc: stable@vger.kernel.org Reported-by: Shisong Qin Signed-off-by: Samuel Thibault Tested-by: Shisong Qin Link: https://lore.kernel.org/r/20201129193523.hm3f6n5xrn6fiyyc@function Signed-off-by: Greg Kroah-Hartman --- drivers/staging/speakup/spk_ttyio.c | 38 +++++++++++++++++++++--------------- 1 file changed, 23 insertions(+), 15 deletions(-) --- a/drivers/staging/speakup/spk_ttyio.c +++ b/drivers/staging/speakup/spk_ttyio.c @@ -46,28 +46,20 @@ static int spk_ttyio_ldisc_open(struct t { struct spk_ldisc_data *ldisc_data; + if (tty != speakup_tty) + /* Somebody tried to use this line discipline outside speakup */ + return -ENODEV; + if (tty->ops->write == NULL) return -EOPNOTSUPP; - mutex_lock(&speakup_tty_mutex); - if (speakup_tty) { - mutex_unlock(&speakup_tty_mutex); - return -EBUSY; - } - speakup_tty = tty; - ldisc_data = kmalloc(sizeof(struct spk_ldisc_data), GFP_KERNEL); - if (!ldisc_data) { - speakup_tty = NULL; - mutex_unlock(&speakup_tty_mutex); - pr_err("speakup: Failed to allocate ldisc_data.\n"); + if (!ldisc_data) return -ENOMEM; - } sema_init(&ldisc_data->sem, 0); ldisc_data->buf_free = true; - speakup_tty->disc_data = ldisc_data; - mutex_unlock(&speakup_tty_mutex); + tty->disc_data = ldisc_data; return 0; } @@ -184,9 +176,25 @@ static int spk_ttyio_initialise_ldisc(st tty_unlock(tty); + mutex_lock(&speakup_tty_mutex); + speakup_tty = tty; ret = tty_set_ldisc(tty, N_SPEAKUP); if (ret) - pr_err("speakup: Failed to set N_SPEAKUP on tty\n"); + speakup_tty = NULL; + mutex_unlock(&speakup_tty_mutex); + + if (!ret) + /* Success */ + return 0; + + pr_err("speakup: Failed to set N_SPEAKUP on tty\n"); + + tty_lock(tty); + if (tty->ops->close) + tty->ops->close(tty, NULL); + tty_unlock(tty); + + tty_kclose(tty); return ret; }