Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932108AbbGTJ0Y (ORCPT ); Mon, 20 Jul 2015 05:26:24 -0400 Received: from mail-wg0-f51.google.com ([74.125.82.51]:33543 "EHLO mail-wg0-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751612AbbGTJ0X (ORCPT ); Mon, 20 Jul 2015 05:26:23 -0400 Subject: Re: [PATCH v4] tty: add missing rcu_read_lock for task_pgrp To: Patrick Donnelly , Greg Kroah-Hartman , open list , openSUSE Kernel , Oleg Nesterov References: <1435439824-3975-1-git-send-email-batrick@batbytes.com> <1436741512-992-1-git-send-email-batrick@batbytes.com> From: Jiri Slaby X-Enigmail-Draft-Status: N1110 Message-ID: <55ACBEBC.5060505@suse.cz> Date: Mon, 20 Jul 2015 11:26:20 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.1.0 MIME-Version: 1.0 In-Reply-To: <1436741512-992-1-git-send-email-batrick@batbytes.com> Content-Type: text/plain; charset=iso-8859-2 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3351 Lines: 116 CC Oleg On 07/13/2015, 12:51 AM, Patrick Donnelly wrote: > task_pgrp requires an rcu or tasklist lock to be obtained if the returned pid > is to be dereferenced, which kill_pgrp does. Obtain an RCU lock for the > duration of use. > > Signed-off-by: Patrick Donnelly > --- > drivers/tty/n_tty.c | 15 ++++++++++++--- > drivers/tty/tty_io.c | 17 ++++++++++++----- > 2 files changed, 24 insertions(+), 8 deletions(-) > > diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c > index c9c27f6..de67b2c 100644 > --- a/drivers/tty/n_tty.c > +++ b/drivers/tty/n_tty.c > @@ -2137,6 +2137,8 @@ extern ssize_t redirected_tty_write(struct file *, const char __user *, > > static int job_control(struct tty_struct *tty, struct file *file) > { > + struct pid *pgrp; > + > /* Job control check -- must be done at start and after > every sleep (POSIX.1 7.1.1.4). */ > /* NOTE: not yet done after every sleep pending a thorough > @@ -2146,18 +2148,25 @@ static int job_control(struct tty_struct *tty, struct file *file) > current->signal->tty != tty) > return 0; > > + rcu_read_lock(); > + pgrp = task_pgrp(current); > + > spin_lock_irq(&tty->ctrl_lock); > if (!tty->pgrp) > printk(KERN_ERR "n_tty_read: no tty->pgrp!\n"); > - else if (task_pgrp(current) != tty->pgrp) { > + else if (pgrp != tty->pgrp) { > spin_unlock_irq(&tty->ctrl_lock); > - if (is_ignored(SIGTTIN) || is_current_pgrp_orphaned()) > + if (is_ignored(SIGTTIN) || is_current_pgrp_orphaned()) { > + rcu_read_unlock(); > return -EIO; > - kill_pgrp(task_pgrp(current), SIGTTIN, 1); > + } > + kill_pgrp(pgrp, SIGTTIN, 1); > + rcu_read_unlock(); > set_thread_flag(TIF_SIGPENDING); > return -ERESTARTSYS; > } > spin_unlock_irq(&tty->ctrl_lock); > + rcu_read_unlock(); > return 0; > } > > diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c > index 57fc6ee..6bdfb98 100644 > --- a/drivers/tty/tty_io.c > +++ b/drivers/tty/tty_io.c > @@ -388,33 +388,40 @@ EXPORT_SYMBOL_GPL(tty_find_polling_driver); > int tty_check_change(struct tty_struct *tty) > { > unsigned long flags; > + struct pid *pgrp; > int ret = 0; > > if (current->signal->tty != tty) > return 0; > > + rcu_read_lock(); > + pgrp = task_pgrp(current); > + > spin_lock_irqsave(&tty->ctrl_lock, flags); > > if (!tty->pgrp) { > printk(KERN_WARNING "tty_check_change: tty->pgrp == NULL!\n"); > goto out_unlock; > } > - if (task_pgrp(current) == tty->pgrp) > + if (pgrp == tty->pgrp) > goto out_unlock; > spin_unlock_irqrestore(&tty->ctrl_lock, flags); > + > if (is_ignored(SIGTTOU)) > - goto out; > + goto out_rcuunlock; > if (is_current_pgrp_orphaned()) { > ret = -EIO; > - goto out; > + goto out_rcuunlock; > } > - kill_pgrp(task_pgrp(current), SIGTTOU, 1); > + kill_pgrp(pgrp, SIGTTOU, 1); > + rcu_read_unlock(); > set_thread_flag(TIF_SIGPENDING); > ret = -ERESTARTSYS; > -out: > return ret; > out_unlock: > spin_unlock_irqrestore(&tty->ctrl_lock, flags); > +out_rcuunlock: > + rcu_read_unlock(); > return ret; > } > > thanks, -- js suse labs -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/