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=-8.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,UNPARSEABLE_RELAY,URIBL_BLOCKED, USER_AGENT_MUTT autolearn=ham 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 5645AC43381 for ; Fri, 29 Mar 2019 07:44:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 21F382183E for ; Fri, 29 Mar 2019 07:44:06 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="SNYSLf2m" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728978AbfC2HoE (ORCPT ); Fri, 29 Mar 2019 03:44:04 -0400 Received: from userp2130.oracle.com ([156.151.31.86]:43226 "EHLO userp2130.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728887AbfC2HoE (ORCPT ); Fri, 29 Mar 2019 03:44:04 -0400 Received: from pps.filterd (userp2130.oracle.com [127.0.0.1]) by userp2130.oracle.com (8.16.0.27/8.16.0.27) with SMTP id x2T7dgVV061754; Fri, 29 Mar 2019 07:43:57 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=date : from : to : cc : subject : message-id : references : mime-version : content-type : in-reply-to; s=corp-2018-07-02; bh=sKbpvAUcu6hVFSeuXJXcTusJNjVorQXuArSHdPGJITQ=; b=SNYSLf2mmxdaN5x3+OGOs8JVjg8oJXJaRbLW8VWrWf4bzJJ70qhF+K9VGh1OjzIBaTQp XkUaHChEsV5/leZSA9Z7cv8bYHjK3EpfRWJISmObH3GujdROLqIgY0Nk4nIY1w8cowUI j1Yw/L4FuO7Ex9X5Fg4wNKTr2upB1yvBNV0gbc1PvGfAVAVH06Bt6mq0f9WKtbfXDnFl Oz9AG9y+/EsxTffig55kO/ddqY93vL6ibCcGet/+br/9Z37eBGBb3YxuIkGt6hfROnpB GLozqlhhxhxNfxr9y8j9hGRHfXqH1ax3Wtdvu47knENA2PcMea6TbHXnEpAGouRRf8ZD hg== Received: from userv0022.oracle.com (userv0022.oracle.com [156.151.31.74]) by userp2130.oracle.com with ESMTP id 2re6g1js6x-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 29 Mar 2019 07:43:57 +0000 Received: from aserv0122.oracle.com (aserv0122.oracle.com [141.146.126.236]) by userv0022.oracle.com (8.14.4/8.14.4) with ESMTP id x2T7hulU007509 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 29 Mar 2019 07:43:57 GMT Received: from abhmp0011.oracle.com (abhmp0011.oracle.com [141.146.116.17]) by aserv0122.oracle.com (8.14.4/8.14.4) with ESMTP id x2T7htpX031965; Fri, 29 Mar 2019 07:43:55 GMT Received: from kadam (/41.202.241.10) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Fri, 29 Mar 2019 00:43:54 -0700 Date: Fri, 29 Mar 2019 10:43:41 +0300 From: Dan Carpenter To: Colin King Cc: Greg Kroah-Hartman , Jiri Slaby , kernel-janitors@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] n_tty: check for negative and zero space return from tty_write_room Message-ID: <20190329074341.GW32590@kadam> References: <20190328171005.5822-1-colin.king@canonical.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190328171005.5822-1-colin.king@canonical.com> User-Agent: Mutt/1.9.4 (2018-02-28) X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=9210 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1903290057 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Mar 28, 2019 at 05:10:05PM +0000, Colin King wrote: > From: Colin Ian King > > The return from tty_write_room could potentially be negative if > a tty write_room driver returns an error number (not that any seem > to do). Rather than just check for a zero return, also check for > a -ve return. This avoids the unsigned nr being set to a large unsigned > value on the assignment from variable space and can lead to overflowing > the buffer buf. Better to be safe than assume all write_room > implementations in tty drivers are going to do the right thing. > > Signed-off-by: Colin Ian King > --- > drivers/tty/n_tty.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c > index 9cdb0fa3c4bf..66630787fbf9 100644 > --- a/drivers/tty/n_tty.c > +++ b/drivers/tty/n_tty.c > @@ -550,7 +550,7 @@ static ssize_t process_output_block(struct tty_struct *tty, > mutex_lock(&ldata->output_lock); > > space = tty_write_room(tty); > - if (!space) { > + if (space <= 0) { > mutex_unlock(&ldata->output_lock); > return 0; Instead of zero we should probably return "space" to preserve the error code. regards, dan carpenter