[PATCH 4.9 43/57] ipack: ipoctal: fix tty-registration error handling

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

From: Johan Hovold <johan@kernel.org>

commit cd20d59291d1790dc74248476e928f57fc455189 upstream.

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
Acked-by: Samuel Iglesias Gonsalvez <siglesias@igalia.com>
Signed-off-by: Johan Hovold <johan@kernel.org>
Link: https://lore.kernel.org/r/20210917114622.5412-4-johan@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/ipack/devices/ipoctal.c |    7 +++++++
 1 file changed, 7 insertions(+)

--- a/drivers/ipack/devices/ipoctal.c
+++ b/drivers/ipack/devices/ipoctal.c
@@ -38,6 +38,7 @@ 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;
@@ -402,9 +403,11 @@ static int ipoctal_inst_slot(struct ipoc
 							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;
 	}
 
 	/*
@@ -705,6 +708,10 @@ static void __ipoctal_remove(struct ipoc
 
 	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);