ipack: ipoctal: fix missing allocation-failure check

Add the missing error handling when allocating the transmit buffer to
avoid dereferencing a NULL pointer in write() should the allocation
ever fail.

Fixes: ba4dc61 ("Staging: ipack: add support for IP-OCTAL mezzanine board")
Cc: [email protected]      # 3.5
Acked-by: Samuel Iglesias Gonsalvez <[email protected]>
Signed-off-by: Johan Hovold <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: jhovold

drivers/ipack/devices/ipoctal.c

@@ -385,7 +385,9 @@ static int ipoctal_inst_slot(struct ipoctal *ipoctal, unsigned int bus_nr,
 
 		channel = &ipoctal->channel[i];
 		tty_port_init(&channel->tty_port);
-		tty_port_alloc_xmit_buf(&channel->tty_port);
+		res = tty_port_alloc_xmit_buf(&channel->tty_port);
+		if (res)
+			continue;
 		channel->tty_port.ops = &ipoctal_tty_port_ops;
 
 		ipoctal_reset_stats(&channel->stats);