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=-6.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,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 A30ACC43387 for ; Fri, 18 Jan 2019 09:04:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 60C442086D for ; Fri, 18 Jan 2019 09:04:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1547802264; bh=eM3yXsodugHNLWe+amuJhIuD/bQ9Xs4TEN0G7xbJ+14=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=1e3Q5PHkkCJS+8DmFnu1yLmzmob93Z7D9EVLe3tHZvUmBQiknszH4W9RlvyxUQ+WJ oRwxh3oBPAl38HvNczXBRN4DzcHSkg3axMgvDukN65miIqknc0d6bnMDEuFGiGT971 cCIwDn/rxTc6WkFOXHyyDSxCXvgNoV9DD+RhCvBU= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726182AbfARJEW (ORCPT ); Fri, 18 Jan 2019 04:04:22 -0500 Received: from mail.kernel.org ([198.145.29.99]:55176 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725784AbfARJEW (ORCPT ); Fri, 18 Jan 2019 04:04:22 -0500 Received: from localhost (5356596B.cm-6-7b.dynamic.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 ECE5D2086D; Fri, 18 Jan 2019 09:04:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1547802261; bh=eM3yXsodugHNLWe+amuJhIuD/bQ9Xs4TEN0G7xbJ+14=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=KTMxi4AaoR6OmWeFI8xnzyJIx37nj7QLiqJ66CtYNxvM3LQIvE2fCJrxDTH1JInuN mo1kAFBD83YLMv4z1UP2yWEjGqTWz+CB9encDMN7KZ43AJhMja62a9V2+z4XS3aL6Z faRTyYSt5oo+xmTngIZ9YgncauJkSFamGzQ9dvyU= Date: Fri, 18 Jan 2019 10:04:19 +0100 From: Greg KH To: Li RongQing Cc: jslaby@suse.com, linux-kernel@vger.kernel.org, gkohli@codeaurora.org Subject: Re: [PATCH][v3] tty: fix race between flush_to_ldisc and tty_open Message-ID: <20190118090419.GA1784@kroah.com> References: <1547801764-13660-1-git-send-email-lirongqing@baidu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1547801764-13660-1-git-send-email-lirongqing@baidu.com> User-Agent: Mutt/1.11.2 (2019-01-07) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jan 18, 2019 at 04:56:04PM +0800, Li RongQing wrote: > There still is a race window after the commit b027e2298bd588 > ("tty: fix data race between tty_init_dev and flush of buf"), > and we encountered this crash issue if receive_buf call comes > before tty initialization completes in n_tty_open and > tty->driver_data may be NULL. > > CPU0 CPU1 > ---- ---- > n_tty_open > tty_init_dev > tty_ldisc_unlock > schedule > flush_to_ldisc > receive_buf > tty_port_default_receive_buf > tty_ldisc_receive_buf > n_tty_receive_buf_common > __receive_buf > uart_flush_chars > uart_start > /*tty->driver_data is NULL*/ > tty->ops->open > /*init tty->driver_data*/ > > it can be fixed by extending ldisc semaphore lock in tty_init_dev > to driver_data initialized completely after tty->ops->open(), but > this will lead to put lock on one function and unlock in some other > function, and hard to maintain, so fix this race only by checking > tty->driver_data when receiving, and return if tty->driver_data > is NULL > > Signed-off-by: Wang Li > Signed-off-by: Zhang Yu > Signed-off-by: Li RongQing > --- > drivers/tty/tty_port.c | 3 +++ > 1 file changed, 3 insertions(+) What changed in this version, from the other versions? That is always to be listed below the --- line, as the documentation states. Please fix up and do a v4 with all of this information. thanks, greg k-h