tty: ipwireless: fix missing checks for ioremap

ipw->attr_memory and ipw->common_memory are assigned with the
return value of ioremap. ioremap may fail, but no checks
are enforced. The fix inserts the checks to avoid potential
NULL pointer dereferences.

Signed-off-by: Kangjie Lu <[e-mail]>
Reviewed-by: David Sterba <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/tty/ipwireless/main.c

···
 
 	ipw->common_memory = ioremap(p_dev->resource[2]->start,
 				resource_size(p_dev->resource[2]));
+	if (!ipw->common_memory) {
+		ret = -ENOMEM;
+		goto exit1;
+	}
 	if (!request_mem_region(p_dev->resource[2]->start,
 				resource_size(p_dev->resource[2]),
 				IPWIRELESS_PCCARD_NAME)) {
···
 
 	ipw->attr_memory = ioremap(p_dev->resource[3]->start,
 				resource_size(p_dev->resource[3]));
+	if (!ipw->attr_memory) {
+		ret = -ENOMEM;
+		goto exit3;
+	}
 	if (!request_mem_region(p_dev->resource[3]->start,
 				resource_size(p_dev->resource[3]),
 				IPWIRELESS_PCCARD_NAME)) {