From 2812d9e9fd94c54b0482215f579e6aa04452a322 Mon Sep 17 00:00:00 2001
From: Peter Hurley <peter@hurleysoftware.com>
Date: Sat, 10 Oct 2015 20:28:42 -0400
Subject: [PATCH] tty: Combine SIGTTOU/SIGTTIN handling

The job_control() check in n_tty_read() has nearly identical purpose
and results as tty_check_change(). Both functions' purpose is to
determine if the current task's pgrp is the foreground pgrp for the tty,
and if not, to signal the current pgrp.

Introduce __tty_check_change() which takes the signal to send
and performs the shared operations for job control() and
tty_check_change().

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/tty/n_tty.c  | 26 ++-----------------------
 drivers/tty/tty_io.c | 46 +++++++++++++++++++++++---------------------
 include/linux/tty.h  |  1 +
 3 files changed, 27 insertions(+), 46 deletions(-)

diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
index ff728d32cb53..fb8ccbfdbb30 100644
--- a/drivers/tty/n_tty.c
+++ b/drivers/tty/n_tty.c
@@ -2138,37 +2138,15 @@ 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
 	   check of the logic of this change. -- jlc */
 	/* don't stop on /dev/console */
-	if (file->f_op->write == redirected_tty_write ||
-	    current->signal->tty != tty)
+	if (file->f_op->write == redirected_tty_write)
 		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 (pgrp != tty->pgrp) {
-		spin_unlock_irq(&tty->ctrl_lock);
-		if (is_ignored(SIGTTIN) || is_current_pgrp_orphaned()) {
-			rcu_read_unlock();
-			return -EIO;
-		}
-		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;
+	return __tty_check_change(tty, SIGTTIN);
 }
 
 
diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index 2eefaa6e3e3a..aa48367a0c79 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -390,10 +390,10 @@ EXPORT_SYMBOL_GPL(tty_find_polling_driver);
  *	Locking: ctrl_lock
  */
 
-int tty_check_change(struct tty_struct *tty)
+int __tty_check_change(struct tty_struct *tty, int sig)
 {
 	unsigned long flags;
-	struct pid *pgrp;
+	struct pid *pgrp, *tty_pgrp;
 	int ret = 0;
 
 	if (current->signal->tty != tty)
@@ -403,33 +403,35 @@ int tty_check_change(struct tty_struct *tty)
 	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 (pgrp == tty->pgrp)
-		goto out_unlock;
+	tty_pgrp = tty->pgrp;
 	spin_unlock_irqrestore(&tty->ctrl_lock, flags);
 
-	if (is_ignored(SIGTTOU))
-		goto out_rcuunlock;
-	if (is_current_pgrp_orphaned()) {
-		ret = -EIO;
-		goto out_rcuunlock;
+	if (tty_pgrp && pgrp != tty->pgrp) {
+		if (is_ignored(sig)) {
+			if (sig == SIGTTIN)
+				ret = -EIO;
+		} else if (is_current_pgrp_orphaned())
+			ret = -EIO;
+		else {
+			kill_pgrp(pgrp, sig, 1);
+			set_thread_flag(TIF_SIGPENDING);
+			ret = -ERESTARTSYS;
+		}
 	}
-	kill_pgrp(pgrp, SIGTTOU, 1);
-	rcu_read_unlock();
-	set_thread_flag(TIF_SIGPENDING);
-	ret = -ERESTARTSYS;
-	return ret;
-out_unlock:
-	spin_unlock_irqrestore(&tty->ctrl_lock, flags);
-out_rcuunlock:
 	rcu_read_unlock();
+
+	if (!tty_pgrp) {
+		pr_warn("%s: tty_check_change: sig=%d, tty->pgrp == NULL!\n",
+			tty_name(tty), sig);
+	}
+
 	return ret;
 }
 
+int tty_check_change(struct tty_struct *tty)
+{
+	return __tty_check_change(tty, SIGTTOU);
+}
 EXPORT_SYMBOL(tty_check_change);
 
 static ssize_t hung_up_tty_read(struct file *file, char __user *buf,
diff --git a/include/linux/tty.h b/include/linux/tty.h
index c2889f4331e1..533d7f6e2481 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -423,6 +423,7 @@ extern int tty_paranoia_check(struct tty_struct *tty, struct inode *inode,
 			      const char *routine);
 extern const char *tty_name(const struct tty_struct *tty);
 extern void tty_wait_until_sent(struct tty_struct *tty, long timeout);
+extern int __tty_check_change(struct tty_struct *tty, int sig);
 extern int tty_check_change(struct tty_struct *tty);
 extern void __stop_tty(struct tty_struct *tty);
 extern void stop_tty(struct tty_struct *tty);