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=-11.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS 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 53831C10DCE for ; Thu, 12 Mar 2020 08:38:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2D5262071C for ; Thu, 12 Mar 2020 08:38:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1584002311; bh=TvHiGwGWurgZI4HBsFz8pMvqF9U/hb0Mngs6Rrzd0Yw=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=qr+6qmmqW1Vk91UIVISmirBzWjRZUOJQXh0y1vKFbg/JbUhfUD/f6YZUC13txm5Pa QPj/Gycs9Qd2K5Gd0PHR776mBvz4OouQiIpVG7vI44AB8GX/SMJjIj+t1JCVnBZauM iOwkLbMdzrMrv1euFbm/aFN2e3Cc8FtvondIiOMs= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726438AbgCLIia (ORCPT ); Thu, 12 Mar 2020 04:38:30 -0400 Received: from mail.kernel.org ([198.145.29.99]:34238 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725980AbgCLIia (ORCPT ); Thu, 12 Mar 2020 04:38:30 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 32B52206B7; Thu, 12 Mar 2020 08:38:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1584002309; bh=TvHiGwGWurgZI4HBsFz8pMvqF9U/hb0Mngs6Rrzd0Yw=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=zKoxiAKAKTCPplcpVK1o1C4vmN+1clen7KXyFIDA9rH6Y8azesemubnwsuw4diBeh 40RyXpaihlEIjcfIgWzabMHIolFqrCxzU+QaEce6VEPqXR2hMHNY41i6yHE68bDwYp iLApSy5cCxt6rDgajJOx+V7frpFGbCZHl7jaFd58= Date: Thu, 12 Mar 2020 09:38:27 +0100 From: Greg KH To: Anthony Mallet Cc: Oliver Neukum , linux-usb@vger.kernel.org Subject: Re: [PATCH v3 2/2] USB: cdc-acm: fix rounding error in TIOCSSERIAL Message-ID: <20200312083827.GA102663@kroah.com> References: <20200310101027.32152-1-anthony.mallet@laas.fr> <20200310101027.32152-2-anthony.mallet@laas.fr> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200310101027.32152-2-anthony.mallet@laas.fr> Sender: linux-usb-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org On Tue, Mar 10, 2020 at 11:10:27AM +0100, Anthony Mallet wrote: > Quoting the bug reporter: > > By default, tty_port_init() initializes those parameters to a multiple > of HZ. For instance in line 69 of tty_port.c: > port->close_delay = (50 * HZ) / 100; > https://github.com/torvalds/linux/blob/master/drivers/tty/tty_port.c#L69 > > With e.g. CONFIG_HZ = 250 (as this is the case for Ubuntu 18.04 > linux-image-4.15.0-37-generic), the default setting for close_delay is > thus 125. > > When ioctl(fd, TIOCGSERIAL, &s) is executed, the setting returned in > user space is '12' (125/10). When ioctl(fd, TIOCSSERIAL, &s) is then > executed with the same setting '12', the value is interpreted as '120' > which is different from the current setting and a EPERM error may be > raised by set_serial_info() if !CAP_SYS_ADMIN. > https://github.com/torvalds/linux/blob/master/drivers/usb/class/cdc-acm.c#L919 > > Fixes: ba2d8ce9db0a6 ("cdc-acm: implement TIOCSSERIAL to avoid blocking close(2)") > Signed-off-by: Anthony Mallet > Cc: stable > --- > Changed in v2: fix typo (extra closing brace) > Changed in v3: version this patch series > --- > drivers/usb/class/cdc-acm.c | 27 +++++++++++++++++---------- > 1 file changed, 17 insertions(+), 10 deletions(-) > > diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c > index da619176deca..a41a3d27016c 100644 > --- a/drivers/usb/class/cdc-acm.c > +++ b/drivers/usb/class/cdc-acm.c > @@ -907,6 +907,7 @@ static int set_serial_info(struct tty_struct *tty, struct serial_struct *ss) > { > struct acm *acm = tty->driver_data; > unsigned int closing_wait, close_delay; > + unsigned int old_closing_wait, old_close_delay; > int retval = 0; > > close_delay = msecs_to_jiffies(ss->close_delay * 10); > @@ -914,19 +915,24 @@ static int set_serial_info(struct tty_struct *tty, struct serial_struct *ss) > ASYNC_CLOSING_WAIT_NONE : > msecs_to_jiffies(ss->closing_wait * 10); > > + /* we must redo the rounding here, so that the values match */ > + old_close_delay = jiffies_to_msecs(acm->port.close_delay) / 10; > + old_closing_wait = acm->port.closing_wait == ASYNC_CLOSING_WAIT_NONE ? > + ASYNC_CLOSING_WAIT_NONE : > + jiffies_to_msecs(acm->port.closing_wait) / 10; > + > mutex_lock(&acm->port.mutex); > > - if (!capable(CAP_SYS_ADMIN)) { > - if ((close_delay != acm->port.close_delay) || > - (closing_wait != acm->port.closing_wait)) > + if ((ss->close_delay != old_close_delay) || > + (ss->closing_wait != old_closing_wait)) { > + if (!capable(CAP_SYS_ADMIN)) > retval = -EPERM; > - else > - retval = -EOPNOTSUPP; > - } else { > - acm->port.close_delay = close_delay; > - acm->port.closing_wait = closing_wait; > - } > + else { > + acm->port.close_delay = close_delay; > + acm->port.closing_wait = closing_wait; > + } > + } else > + retval = -EOPNOTSUPP; > > mutex_unlock(&acm->port.mutex); > return retval; > -- > 2.17.1 > This patch doesn't apply to my usb-linus branch at all. What tree/branch did you make it against? thanks, greg k-h