ieee1394: nodemgr: check info_length in ROM header earlier

The whole ROM area which is covered by the crc_length field of the ROM
header was fetched before the info_length field was checked for correct
general ROM format.  This might be wasteful or even dangerous with nodes
with minimal ROM, nonstandard ROM, or corrupt ROM.

Perform this check at the earliest opportunity.
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>

drivers/ieee1394/csr1212.c

@@ -1234,6 +1234,12 @@ static int csr1212_parse_bus_info_block(struct csr1212_csr *csr)
 					 csr->private);
 		if (ret != CSR1212_SUCCESS)
 			return ret;
+
+		/* check ROM header's info_length */
+		if (i == 0 &&
+		    CSR1212_BE32_TO_CPU(csr->cache_head->data[0]) >> 24 !=
+		    bytes_to_quads(csr->bus_info_len) - 1)
+			return CSR1212_EINVAL;
 	}
 
 	bi = (struct csr1212_bus_info_block_img*)csr->cache_head->data;
@@ -1250,9 +1256,6 @@ static int csr1212_parse_bus_info_block(struct csr1212_csr *csr)
 			return ret;
 	}
 
-	if (bytes_to_quads(csr->bus_info_len - sizeof(csr1212_quad_t)) != bi->length)
-		return CSR1212_EINVAL;
-
 #if 0
 	/* Apparently there are too many differnt wrong implementations of the
 	 * CRC algorithm that verifying them is moot. */