Patch "tty: serial: men_z135_uart.c: Fix race between IRQ and set_termios()" has been added to the 4.2-stable tree

This is a note to let you know that I've just added the patch titled

tty: serial: men_z135_uart.c: Fix race between IRQ and set_termios()

to the 4.2-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
tty-serial-men_z135_uart.c-fix-race-between-irq-and-set_termios.patch
and it can be found in the queue-4.2 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Johannes Thumshirn <[email protected]>
Date: Thu, 6 Aug 2015 09:16:37 +0200
Subject: tty: serial: men_z135_uart.c: Fix race between IRQ and set_termios()

From: Johannes Thumshirn <[email protected]>

commit 8117e347406278fd399b077add4e638cd017ae2d upstream.

Fix panic caused by a race between men_z135_intr() and men_z135_set_termios().

men_z135_intr() and men_z135_set_termios() both hold the struct uart_port::lock spinlock, but men_z135_intr() does a spin_lock_irqsave() and men_z135_set_termios() does a normal spin_lock(), which can lead to a deadlock when an interrupt is called while the lock is being helt by men_z135_set_termios().

This was discovered using a insmod, hardware looppback send/receive, rmmod stress test.

---
 drivers/tty/serial/men_z135_uart.c |    9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

@@ -392,7 +392,6 @@ static irqreturn_t men_z135_intr(int irq
 	struct men_z135_port *uart = (struct men_z135_port *)data;
 	struct uart_port *port = &uart->port;
 	bool handled = false;
-	unsigned long flags;
 	int irq_id;
 
 	uart->stat_reg = ioread32(port->membase + MEN_Z135_STAT_REG);

@@ -401,7 +400,7 @@ static irqreturn_t men_z135_intr(int irq
 	if (!irq_id)
 		goto out;
 
-	spin_lock_irqsave(&port->lock, flags);
+	spin_lock(&port->lock);
 	/* It's save to write to IIR[7:6] RXC[9:8] */
 	iowrite8(irq_id, port->membase + MEN_Z135_STAT_REG);
 

@@ -427,7 +426,7 @@ static irqreturn_t men_z135_intr(int irq
 		handled = true;
 	}
 
-	spin_unlock_irqrestore(&port->lock, flags);
+	spin_unlock(&port->lock);
 out:
 	return IRQ_RETVAL(handled);
 }

@@ -717,7 +716,7 @@ static void men_z135_set_termios(struct
 
 	baud = uart_get_baud_rate(port, termios, old, 0, uart_freq / 16);
 
-	spin_lock(&port->lock);
+	spin_lock_irq(&port->lock);
 	if (tty_termios_baud_rate(termios))
 		tty_termios_encode_baud_rate(termios, baud, baud);
 

@@ -725,7 +724,7 @@ static void men_z135_set_termios(struct
 	iowrite32(bd_reg, port->membase + MEN_Z135_BAUD_REG);
 
 	uart_update_timeout(port, termios->c_cflag, baud);
-	spin_unlock(&port->lock);
+	spin_unlock_irq(&port->lock);
 }
 
 static const char *men_z135_type(struct uart_port *port)

Patches currently in stable-queue which might be from [email protected] are

queue-4.2/tty-serial-men_z135_uart.c-fix-race-between-irq-and-set_termios.patch