Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753587AbbF3AAG (ORCPT ); Mon, 29 Jun 2015 20:00:06 -0400 Received: from mail-ig0-f181.google.com ([209.85.213.181]:36876 "EHLO mail-ig0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750981AbbF2X7y (ORCPT ); Mon, 29 Jun 2015 19:59:54 -0400 From: Patrick Donnelly To: Greg Kroah-Hartman , Jiri Slaby , linux-kernel@vger.kernel.org (open list) Cc: Patrick Donnelly Subject: [PATCH v3] tty: add missing rcu_read_lock for task_pgrp Date: Mon, 29 Jun 2015 19:59:39 -0400 Message-Id: <1435622379-3170-1-git-send-email-batrick@batbytes.com> X-Mailer: git-send-email 2.4.4 In-Reply-To: <1435439824-3975-1-git-send-email-batrick@batbytes.com> References: <1435439824-3975-1-git-send-email-batrick@batbytes.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2993 Lines: 108 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 | 12 ++++++++++-- drivers/tty/tty_io.c | 17 ++++++++++++----- 2 files changed, 22 insertions(+), 7 deletions(-) diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c index c9c27f6..0d631f8 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 +2148,24 @@ 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()) 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; } -- Patrick Donnelly -- 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/