efi/libstub: randomalloc: Return EFI_OUT_OF_RESOURCES on failure

The logic in efi_random_alloc() will iterate over the memory map twice,
once to count the number of candidate slots, and another time to locate
the chosen slot after randomization.

If there is insufficient memory to do the allocation, the second loop
will run to completion without actually having located a slot, but we
currently return EFI_SUCCESS in this case, as we fail to initialize
status to the appropriate error value of EFI_OUT_OF_RESOURCES.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

drivers/firmware/efi/libstub/randomalloc.c

@@ -101,6 +101,7 @@ efi_status_t efi_random_alloc(unsigned long size,
 	 * to calculate the randomly chosen address, and allocate it directly
 	 * using EFI_ALLOCATE_ADDRESS.
 	 */
+	status = EFI_OUT_OF_RESOURCES;
 	for (map_offset = 0; map_offset < map->map_size; map_offset += map->desc_size) {
 		efi_memory_desc_t *md = (void *)map->map + map_offset;
 		efi_physical_addr_t target;