diff --git a/drivers/firmware/efi/libstub/randomalloc.c b/drivers/firmware/efi/libstub/randomalloc.c
index a408df474d83..724155b9e10d 100644
--- a/drivers/firmware/efi/libstub/randomalloc.c
+++ b/drivers/firmware/efi/libstub/randomalloc.c
@@ -30,6 +30,8 @@ static unsigned long get_entry_num_slots(efi_memory_desc_t *md,
 
 	region_end = min(md->phys_addr + md->num_pages * EFI_PAGE_SIZE - 1,
 			 (u64)ULONG_MAX);
+	if (region_end < size)
+		return 0;
 
 	first_slot = round_up(md->phys_addr, align);
 	last_slot = round_down(region_end - size + 1, align);