char: hpet: add checks after calling ioremap

The function hpet_resources() calls ioremap() two times, but in both
cases it does not check if ioremap() returned a null pointer. Fix this
by adding null pointer checks and returning an appropriate error.
Signed-off-by: Tom Seewald <tseewald@gmail.com>
Link: https://lore.kernel.org/r/20210503115736.2104747-30-gregkh@linuxfoundation.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/char/hpet.c

@@ -969,6 +969,8 @@ static acpi_status hpet_resources(struct acpi_resource *res, void *data)
 	if (ACPI_SUCCESS(status)) {
 		hdp->hd_phys_address = addr.address.minimum;
 		hdp->hd_address = ioremap(addr.address.minimum, addr.address.address_length);
+		if (!hdp->hd_address)
+			return AE_ERROR;
 
 		if (hpet_is_known(hdp)) {
 			iounmap(hdp->hd_address);
@@ -982,6 +984,8 @@ static acpi_status hpet_resources(struct acpi_resource *res, void *data)
 		hdp->hd_phys_address = fixmem32->address;
 		hdp->hd_address = ioremap(fixmem32->address,
 						HPET_RANGE_SIZE);
+		if (!hdp->hd_address)
+			return AE_ERROR;
 
 		if (hpet_is_known(hdp)) {
 			iounmap(hdp->hd_address);