From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752800AbbCXHG0 (ORCPT ); Tue, 24 Mar 2015 03:06:26 -0400 Received: from mga09.intel.com ([134.134.136.24]:28229 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751494AbbCXHGZ (ORCPT ); Tue, 24 Mar 2015 03:06:25 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.11,456,1422950400"; d="scan'208";a="696773397" Message-ID: <55125E3D.2070109@intel.com> Date: Wed, 25 Mar 2015 15:05:33 +0800 From: Pan Xinhui User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.5.0 MIME-Version: 1.0 To: gregkh@linuxfoundation.org, jslaby@suse.cz, linux-kernel@vger.kernel.org CC: yanmin_zhang@linux.intel.com, mnipxh@gmai.com Subject: [PATCH v2] tty/n_gsm.c: fix a memory leak when gsmtty is removed References: <551111B9.3000008@intel.com> In-Reply-To: <551111B9.3000008@intel.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org when gsmtty_remove put dlci, it will cause memory leak if dlci->port's refcount is zero. So we do the cleanup work in .cleanup callback instead. dlci will be last put in two call chains. 1) gsmld_close -> gsm_cleanup_mux -> gsm_dlci_release -> dlci_put 2) gsmld_remove -> dlci_put so there is a race. the memory leak depends on the race. In call chain 2. we hit the memory leak. bellow comment tells. release_tty -> tty_driver_remove_tty -> gsmtty_remove -> dlci_put -> tty_port_destructor (WARN_ON(port->itty) and return directly) | --> tty->port->itty = NULL; | tty_kref_put ---> release_one_tty -> gsmtty_cleanup (now we do the cleanup work here.) So our patch fix it by doing the cleanup work after tty core did. Signed-off-by: xinhui.pan --- drivers/tty/n_gsm.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c index c434376..bce16e4 100644 --- a/drivers/tty/n_gsm.c +++ b/drivers/tty/n_gsm.c @@ -3170,7 +3170,7 @@ static int gsmtty_break_ctl(struct tty_struct *tty, int state) return gsmtty_modem_update(dlci, encode); } -static void gsmtty_remove(struct tty_driver *driver, struct tty_struct *tty) +static void gsmtty_cleanup(struct tty_struct *tty) { struct gsm_dlci *dlci = tty->driver_data; struct gsm_mux *gsm = dlci->gsm; @@ -3178,7 +3178,6 @@ static void gsmtty_remove(struct tty_driver *driver, struct tty_struct *tty) dlci_put(dlci); dlci_put(gsm->dlci[0]); mux_put(gsm); - driver->ttys[tty->index] = NULL; } /* Virtual ttys for the demux */ @@ -3199,7 +3198,7 @@ static const struct tty_operations gsmtty_ops = { .tiocmget = gsmtty_tiocmget, .tiocmset = gsmtty_tiocmset, .break_ctl = gsmtty_break_ctl, - .remove = gsmtty_remove, + .cleanup = gsmtty_cleanup, }; -- 1.9.1