ipack/devices/ipoctal: fix kernel bug when using pppd

Trying to setup the pppd server to use ipoctal's serial ports, it says the ports
are busy the first time. If the operation is repeated, a kernel bug due to a
dereference of a NULL pointer appears.

Removing the one-access-only setup from the driver, removes this kernel bug.
Signed-off-by: NSamuel Iglesias Gonsalvez <siglesias@igalia.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/ipack/devices/ipoctal.c

@@ -38,7 +38,6 @@ struct ipoctal_channel {
 	spinlock_t			lock;
 	unsigned int			pointer_read;
 	unsigned int			pointer_write;
-	atomic_t			open;
 	struct tty_port			tty_port;
 	union scc2698_channel __iomem	*regs;
 	union scc2698_block __iomem	*block_regs;
@@ -70,22 +69,12 @@ static int ipoctal_port_activate(struct tty_port *port, struct tty_struct *tty)
 
 static int ipoctal_open(struct tty_struct *tty, struct file *file)
 {
-	int res;
 	struct ipoctal_channel *channel;
 
 	channel = dev_get_drvdata(tty->dev);
-
-	if (atomic_read(&channel->open))
-		return -EBUSY;
-
 	tty->driver_data = channel;
 
-	res = tty_port_open(&channel->tty_port, tty, file);
-	if (res)
-		return res;
-
-	atomic_inc(&channel->open);
-	return 0;
+	return tty_port_open(&channel->tty_port, tty, file);
 }
 
 static void ipoctal_reset_stats(struct ipoctal_stats *stats)
@@ -111,9 +100,7 @@ static void ipoctal_close(struct tty_struct *tty, struct file *filp)
 	struct ipoctal_channel *channel = tty->driver_data;
 
 	tty_port_close(&channel->tty_port, tty, filp);
-
-	if (atomic_dec_and_test(&channel->open))
-		ipoctal_free_channel(channel);
+	ipoctal_free_channel(channel);
 }
 
 static int ipoctal_get_icount(struct tty_struct *tty,
@@ -205,10 +192,6 @@ static void ipoctal_irq_channel(struct ipoctal_channel *channel)
 	u8 isr, sr;
 	struct tty_struct *tty;
 
-	/* If there is no client, skip the check */
-	if (!atomic_read(&channel->open))
-		return;
-
 	tty = tty_port_tty_get(&channel->tty_port);
 	if (!tty)
 		return;