x86,efi: Check max_size only if it is non-zero.

commit 7791c842 upstream.

Some EFI implementations return always a MaximumVariableSize of 0,
check against max_size only if it is non-zero.
My Intel DQ67SW desktop board has such an implementation.
Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

arch/x86/platform/efi/efi.c

@@ -834,7 +834,12 @@ efi_status_t efi_query_variable_store(u32 attributes, unsigned long size)
 	if (status != EFI_SUCCESS)
 		return status;
 
-	if (!storage_size || size > remaining_size || size > max_size ||
+	if (!max_size && remaining_size > size)
+		printk_once(KERN_ERR FW_BUG "Broken EFI implementation"
+			    " is returning MaxVariableSize=0\n");
+
+	if (!storage_size || size > remaining_size ||
+	    (max_size && size > max_size) ||
 	    (remaining_size - size) < (storage_size / 2))
 		return EFI_OUT_OF_RESOURCES;