[PATCH 3/6] ipack: ipoctal: fix tty-registration error handling

[Johan Hovold <johan@kernel.org>]

Registration of the ipoctal tty devices is unlikely to fail, but if it
ever does, make sure not to deregister a never registered tty device
(and dereference a NULL pointer) when the driver is later unbound.

Fixes: 2afb41d9d30d ("Staging: ipack/devices/ipoctal: Check tty_register_device return value.")
Cc: stable@vger.kernel.org      # 3.7
Signed-off-by: Johan Hovold <johan@kernel.org>
---
 drivers/ipack/devices/ipoctal.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/ipack/devices/ipoctal.c b/drivers/ipack/devices/ipoctal.c
index 262451343127..d6875aa6a295 100644
--- a/drivers/ipack/devices/ipoctal.c
+++ b/drivers/ipack/devices/ipoctal.c
@@ -33,6 +33,7 @@ struct ipoctal_channel {
 	unsigned int			pointer_read;
 	unsigned int			pointer_write;
 	struct tty_port			tty_port;
+	bool				tty_registered;
 	union scc2698_channel __iomem	*regs;
 	union scc2698_block __iomem	*block_regs;
 	unsigned int			board_id;
@@ -396,9 +397,11 @@ static int ipoctal_inst_slot(struct ipoctal *ipoctal, unsigned int bus_nr,
 							i, NULL, channel, NULL);
 		if (IS_ERR(tty_dev)) {
 			dev_err(&ipoctal->dev->dev, "Failed to register tty device.\n");
+			tty_port_free_xmit_buf(&channel->tty_port);
 			tty_port_destroy(&channel->tty_port);
 			continue;
 		}
+		channel->tty_registered = true;
 	}
 
 	/*
@@ -698,6 +701,10 @@ static void __ipoctal_remove(struct ipoctal *ipoctal)
 
 	for (i = 0; i < NR_CHANNELS; i++) {
 		struct ipoctal_channel *channel = &ipoctal->channel[i];
+
+		if (!channel->tty_registered)
+			continue;
+
 		tty_unregister_device(ipoctal->tty_drv, i);
 		tty_port_free_xmit_buf(&channel->tty_port);
 		tty_port_destroy(&channel->tty_port);
-- 
2.32.0