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=-14.8 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,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 2A483C43331 for ; Wed, 1 Apr 2020 16:30:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id F04D9215A4 for ; Wed, 1 Apr 2020 16:30:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1585758633; bh=Mb0hvmbgez7y+paqjQ0qHPTlmbJ48sqndd0cHkzkev0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=PsAJ9JLE3TvOSc4jxqnWQakCgHVgwGZgyTO60tVnvX9LHJfZLVGRXISTHBsxsmdSq iBQPhTMsYzxZWKBcY+w6wLJs1mdPf2fh7QRP79mjXJjcjkLwr4boRFRz0onFMDrwy9 tBMRrKTVzUiuGvx3jTWFliXPPHKg9VxkrPy3RiyM= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387423AbgDAQac (ORCPT ); Wed, 1 Apr 2020 12:30:32 -0400 Received: from mail.kernel.org ([198.145.29.99]:56322 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732683AbgDAQa1 (ORCPT ); Wed, 1 Apr 2020 12:30:27 -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 D15FC215A4; Wed, 1 Apr 2020 16:30:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1585758625; bh=Mb0hvmbgez7y+paqjQ0qHPTlmbJ48sqndd0cHkzkev0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=DC2OcyTsx9NDU64P8M/ANLC/4vFLI7ii7GrRNVc3DfSRfaBnwK5J2t1pdiJQmd4kF TDt3UVu+uuUREf4RAm3ktC5L3ON2sk9RXkYTCLrP0PWecWy2u2d+ttPafgfxq74jbX O5zpw++reABURrLRROIkNRdsmUOxFSIA7mVlnZx4= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Anthony Mallet , Sasha Levin Subject: [PATCH 4.4 27/91] USB: cdc-acm: fix rounding error in TIOCSSERIAL Date: Wed, 1 Apr 2020 18:17:23 +0200 Message-Id: <20200401161522.133672386@linuxfoundation.org> X-Mailer: git-send-email 2.26.0 In-Reply-To: <20200401161512.917494101@linuxfoundation.org> References: <20200401161512.917494101@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Anthony Mallet [ Upstream commit b401f8c4f492cbf74f3f59c9141e5be3071071bb ] 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 Link: https://lore.kernel.org/r/20200312133101.7096-2-anthony.mallet@laas.fr Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin --- drivers/usb/class/cdc-acm.c | 25 ++++++++++++++++--------- 1 file changed, 16 insertions(+), 9 deletions(-) diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c index 3cb7a23e1253f..7dd2f413595eb 100644 --- a/drivers/usb/class/cdc-acm.c +++ b/drivers/usb/class/cdc-acm.c @@ -857,6 +857,7 @@ static int set_serial_info(struct acm *acm, { struct serial_struct new_serial; unsigned int closing_wait, close_delay; + unsigned int old_closing_wait, old_close_delay; int retval = 0; if (copy_from_user(&new_serial, newinfo, sizeof(new_serial))) @@ -867,18 +868,24 @@ static int set_serial_info(struct acm *acm, ASYNC_CLOSING_WAIT_NONE : msecs_to_jiffies(new_serial.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 ((new_serial.close_delay != old_close_delay) || + (new_serial.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; -- 2.20.1