[SCSI] libsas: fix false positive 'device attached' conditions

Normalize phy->attached_sas_addr to return a zero-address in the case
when device-type == NO_DEVICE or the linkrate is invalid to handle
expanders that put non-zero sas addresses in the discovery response:

 sas: ex 5001b4da000f903f phy02:U:0 attached: 0100000000000000 (no device)
 sas: ex 5001b4da000f903f phy01:U:0 attached: 0100000000000000 (no device)
 sas: ex 5001b4da000f903f phy03:U:0 attached: 0100000000000000 (no device)
 sas: ex 5001b4da000f903f phy00:U:0 attached: 0100000000000000 (no device)

Reported-by: Andrzej Jakowski <andrzej.jakowski@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Cc: stable@vger.kernel.org
Signed-off-by: James Bottomley <JBottomley@Parallels.com>

drivers/scsi/libsas/sas_expander.c

@@ -245,7 +245,14 @@ static void sas_set_ex_phy(struct domain_device *dev, int phy_id, void *rsp)
 	phy->attached_sata_ps   = dr->attached_sata_ps;
 	phy->attached_iproto = dr->iproto << 1;
 	phy->attached_tproto = dr->tproto << 1;
-	memcpy(phy->attached_sas_addr, dr->attached_sas_addr, SAS_ADDR_SIZE);
+	/* help some expanders that fail to zero sas_address in the 'no
+	 * device' case
+	 */
+	if (phy->attached_dev_type == NO_DEVICE ||
+	    phy->linkrate < SAS_LINK_RATE_1_5_GBPS)
+		memset(phy->attached_sas_addr, 0, SAS_ADDR_SIZE);
+	else
+		memcpy(phy->attached_sas_addr, dr->attached_sas_addr, SAS_ADDR_SIZE);
 	phy->attached_phy_id = dr->attached_phy_id;
 	phy->phy_change_count = dr->change_count;
 	phy->routing_attr = dr->routing_attr;