ACPI: Make sure the FADT is at least rev 2 before using the reset register

The reset register was only introduced with version 2 of the FADT, so we
should check that the FADT revision before trusting its contents.

Signed-off-by: Matthew Garrett <[e-mail]>
Signed-off-by: Len Brown <[e-mail]>

drivers/acpi/reboot.c

···
 
 	rr = &acpi_gbl_FADT.reset_register;
 
+	/* ACPI reset register was only introduced with v2 of the FADT */
+
+	if (acpi_gbl_FADT.header.revision < 2)
+		return;
+
 	/* Is the reset register supported? The spec says we should be
 	 * checking the bit width and bit offset, but Windows ignores
 	 * these fields */