TTY/Serial driver fixes for 4.3-rc5

Here are a few bug fixes for the tty core that resolve reported issues,
 and some serial driver fixes as well (including the much-reported imx
 driver problem.)
 
 All of these have been in linux-next with no reported problems.
 
 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Merge tag 'tty-4.3-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty

Pull tty/serial driver fixes from Greg KH:
 "Here are a few bug fixes for the tty core that resolve reported
  issues, and some serial driver fixes as well (including the
  much-reported imx driver problem)

  All of these have been in linux-next with no reported problems"

* tag 'tty-4.3-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty:
  drivers/tty: require read access for controlling terminal
  serial: 8250: add uart_config entry for PORT_RT2880
  tty: fix data race on tty_buffer.commit
  tty: fix data race in tty_buffer_flush
  tty: fix data race in flush_to_ldisc
  tty: fix stall caused by missing memory barrier in drivers/tty/n_tty.c
  serial: atmel: fix error path of probe function
  tty: don't leak cdev in tty_cdev_add()
  Revert "serial: imx: remove unbalanced clk_prepare"

drivers/tty/n_tty.c

@@ -343,8 +343,7 @@ static void n_tty_packet_mode_flush(struct tty_struct *tty)
 		spin_lock_irqsave(&tty->ctrl_lock, flags);
 		tty->ctrl_status |= TIOCPKT_FLUSHREAD;
 		spin_unlock_irqrestore(&tty->ctrl_lock, flags);
-		if (waitqueue_active(&tty->link->read_wait))
-			wake_up_interruptible(&tty->link->read_wait);
+		wake_up_interruptible(&tty->link->read_wait);
 	}
 }
 
@@ -1382,8 +1381,7 @@ n_tty_receive_char_special(struct tty_struct *tty, unsigned char c)
 			put_tty_queue(c, ldata);
 			smp_store_release(&ldata->canon_head, ldata->read_head);
 			kill_fasync(&tty->fasync, SIGIO, POLL_IN);
-			if (waitqueue_active(&tty->read_wait))
-				wake_up_interruptible_poll(&tty->read_wait, POLLIN);
+			wake_up_interruptible_poll(&tty->read_wait, POLLIN);
 			return 0;
 		}
 	}
@@ -1667,8 +1665,7 @@ static void __receive_buf(struct tty_struct *tty, const unsigned char *cp,
 
 	if ((read_cnt(ldata) >= ldata->minimum_to_wake) || L_EXTPROC(tty)) {
 		kill_fasync(&tty->fasync, SIGIO, POLL_IN);
-		if (waitqueue_active(&tty->read_wait))
-			wake_up_interruptible_poll(&tty->read_wait, POLLIN);
+		wake_up_interruptible_poll(&tty->read_wait, POLLIN);
 	}
 }
 
@@ -1887,10 +1884,8 @@ static void n_tty_set_termios(struct tty_struct *tty, struct ktermios *old)
 	}
 
 	/* The termios change make the tty ready for I/O */
-	if (waitqueue_active(&tty->write_wait))
-		wake_up_interruptible(&tty->write_wait);
-	if (waitqueue_active(&tty->read_wait))
-		wake_up_interruptible(&tty->read_wait);
+	wake_up_interruptible(&tty->write_wait);
+	wake_up_interruptible(&tty->read_wait);
 }
 
 /**

drivers/tty/serial/8250/8250_port.c

@@ -261,6 +261,14 @@ configured less than Maximum supported fifo bytes */
 				  UART_FCR7_64BYTE,
 		.flags		= UART_CAP_FIFO,
 	},
+	[PORT_RT2880] = {
+		.name		= "Palmchip BK-3103",
+		.fifo_size	= 16,
+		.tx_loadsz	= 16,
+		.fcr		= UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_10,
+		.rxtrig_bytes	= {1, 4, 8, 14},
+		.flags		= UART_CAP_FIFO,
+	},
 };
 
 /* Uart divisor latch read */

drivers/tty/serial/atmel_serial.c

@@ -2786,7 +2786,7 @@ static int atmel_serial_probe(struct platform_device *pdev)
 	ret = atmel_init_gpios(port, &pdev->dev);
 	if (ret < 0) {
 		dev_err(&pdev->dev, "Failed to initialize GPIOs.");
-		goto err;
+		goto err_clear_bit;
 	}
 
 	ret = atmel_init_port(port, pdev);

drivers/tty/serial/imx.c

@@ -1631,12 +1631,12 @@ imx_console_write(struct console *co, const char *s, unsigned int count)
 	int locked = 1;
 	int retval;
 
-	retval = clk_prepare_enable(sport->clk_per);
+	retval = clk_enable(sport->clk_per);
 	if (retval)
 		return;
-	retval = clk_prepare_enable(sport->clk_ipg);
+	retval = clk_enable(sport->clk_ipg);
 	if (retval) {
-		clk_disable_unprepare(sport->clk_per);
+		clk_disable(sport->clk_per);
 		return;
 	}
 
@@ -1675,8 +1675,8 @@ imx_console_write(struct console *co, const char *s, unsigned int count)
 	if (locked)
 		spin_unlock_irqrestore(&sport->port.lock, flags);
 
-	clk_disable_unprepare(sport->clk_ipg);
-	clk_disable_unprepare(sport->clk_per);
+	clk_disable(sport->clk_ipg);
+	clk_disable(sport->clk_per);
 }
 
 /*
@@ -1777,7 +1777,15 @@ imx_console_setup(struct console *co, char *options)
 
 	retval = uart_set_options(&sport->port, co, baud, parity, bits, flow);
 
-	clk_disable_unprepare(sport->clk_ipg);
+	clk_disable(sport->clk_ipg);
+	if (retval) {
+		clk_unprepare(sport->clk_ipg);
+		goto error_console;
+	}
+
+	retval = clk_prepare(sport->clk_per);
+	if (retval)
+		clk_disable_unprepare(sport->clk_ipg);
 
 error_console:
 	return retval;

drivers/tty/tty_buffer.c

@@ -242,7 +242,10 @@ void tty_buffer_flush(struct tty_struct *tty, struct tty_ldisc *ld)
 	atomic_inc(&buf->priority);
 
 	mutex_lock(&buf->lock);
-	while ((next = buf->head->next) != NULL) {
+	/* paired w/ release in __tty_buffer_request_room; ensures there are
+	 * no pending memory accesses to the freed buffer
+	 */
+	while ((next = smp_load_acquire(&buf->head->next)) != NULL) {
 		tty_buffer_free(port, buf->head);
 		buf->head = next;
 	}
@@ -290,7 +293,10 @@ static int __tty_buffer_request_room(struct tty_port *port, size_t size,
 		if (n != NULL) {
 			n->flags = flags;
 			buf->tail = n;
-			b->commit = b->used;
+			/* paired w/ acquire in flush_to_ldisc(); ensures
+			 * flush_to_ldisc() sees buffer data.
+			 */
+			smp_store_release(&b->commit, b->used);
 			/* paired w/ acquire in flush_to_ldisc(); ensures the
 			 * latest commit value can be read before the head is
 			 * advanced to the next buffer
@@ -393,7 +399,10 @@ void tty_schedule_flip(struct tty_port *port)
 {
 	struct tty_bufhead *buf = &port->buf;
 
-	buf->tail->commit = buf->tail->used;
+	/* paired w/ acquire in flush_to_ldisc(); ensures
+	 * flush_to_ldisc() sees buffer data.
+	 */
+	smp_store_release(&buf->tail->commit, buf->tail->used);
 	schedule_work(&buf->work);
 }
 EXPORT_SYMBOL(tty_schedule_flip);
@@ -467,7 +476,7 @@ static void flush_to_ldisc(struct work_struct *work)
 	struct tty_struct *tty;
 	struct tty_ldisc *disc;
 
-	tty = port->itty;
+	tty = READ_ONCE(port->itty);
 	if (tty == NULL)
 		return;
 
@@ -491,7 +500,10 @@ static void flush_to_ldisc(struct work_struct *work)
 		 * is advancing to the next buffer
 		 */
 		next = smp_load_acquire(&head->next);
-		count = head->commit - head->read;
+		/* paired w/ release in __tty_buffer_request_room() or in
+		 * tty_buffer_flush(); ensures we see the committed buffer data
+		 */
+		count = smp_load_acquire(&head->commit) - head->read;
 		if (!count) {
 			if (next == NULL) {
 				check_other_closed(tty);

drivers/tty/tty_io.c

@@ -2128,8 +2128,24 @@ static int tty_open(struct inode *inode, struct file *filp)
 	if (!noctty &&
 	    current->signal->leader &&
 	    !current->signal->tty &&
-	    tty->session == NULL)
-		__proc_set_tty(tty);
+	    tty->session == NULL) {
+		/*
+		 * Don't let a process that only has write access to the tty
+		 * obtain the privileges associated with having a tty as
+		 * controlling terminal (being able to reopen it with full
+		 * access through /dev/tty, being able to perform pushback).
+		 * Many distributions set the group of all ttys to "tty" and
+		 * grant write-only access to all terminals for setgid tty
+		 * binaries, which should not imply full privileges on all ttys.
+		 *
+		 * This could theoretically break old code that performs open()
+		 * on a write-only file descriptor. In that case, it might be
+		 * necessary to also permit this if
+		 * inode_permission(inode, MAY_READ) == 0.
+		 */
+		if (filp->f_mode & FMODE_READ)
+			__proc_set_tty(tty);
+	}
 	spin_unlock_irq(&current->sighand->siglock);
 	read_unlock(&tasklist_lock);
 	tty_unlock(tty);
@@ -2418,7 +2434,7 @@ static int fionbio(struct file *file, int __user *p)
  *		Takes ->siglock() when updating signal->tty
  */
 
-static int tiocsctty(struct tty_struct *tty, int arg)
+static int tiocsctty(struct tty_struct *tty, struct file *file, int arg)
 {
 	int ret = 0;
 
@@ -2452,6 +2468,13 @@ static int tiocsctty(struct tty_struct *tty, int arg)
 			goto unlock;
 		}
 	}
+
+	/* See the comment in tty_open(). */
+	if ((file->f_mode & FMODE_READ) == 0 && !capable(CAP_SYS_ADMIN)) {
+		ret = -EPERM;
+		goto unlock;
+	}
+
 	proc_set_tty(tty);
 unlock:
 	read_unlock(&tasklist_lock);
@@ -2844,7 +2867,7 @@ long tty_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 		no_tty();
 		return 0;
 	case TIOCSCTTY:
-		return tiocsctty(tty, arg);
+		return tiocsctty(tty, file, arg);
 	case TIOCGPGRP:
 		return tiocgpgrp(tty, real_tty, p);
 	case TIOCSPGRP:
@@ -3151,13 +3174,18 @@ struct class *tty_class;
 static int tty_cdev_add(struct tty_driver *driver, dev_t dev,
 		unsigned int index, unsigned int count)
 {
+	int err;
+
 	/* init here, since reused cdevs cause crashes */
 	driver->cdevs[index] = cdev_alloc();
 	if (!driver->cdevs[index])
 		return -ENOMEM;
-	cdev_init(driver->cdevs[index], &tty_fops);
+	driver->cdevs[index]->ops = &tty_fops;
 	driver->cdevs[index]->owner = driver->owner;
-	return cdev_add(driver->cdevs[index], dev, count);
+	err = cdev_add(driver->cdevs[index], dev, count);
+	if (err)
+		kobject_put(&driver->cdevs[index]->kobj);
+	return err;
 }
 
 /**