net: bonding: Use strscpy_pad() instead of manually-truncated strncpy()

Silence this warning by using strscpy_pad() directly:

drivers/net/bonding/bond_main.c:4877:3: warning: 'strncpy' specified bound 16 equals destination size [-Wstringop-truncation]
    4877 |   strncpy(params->primary, primary, IFNAMSIZ);
         |   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Additionally replace other strncpy() uses, as it is considered deprecated:
https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-stringsReported-by: kernel test robot <lkp@intel.com>
Link: https://lore.kernel.org/lkml/202102150705.fdR6obB0-lkp@intel.comAcked-by: Jay Vosburgh <jay.vosburgh@canonical.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/bonding/bond_main.c

@@ -620,7 +620,7 @@ static int bond_check_dev_link(struct bonding *bond,
 		 */
 
 		/* Yes, the mii is overlaid on the ifreq.ifr_ifru */
-		strncpy(ifr.ifr_name, slave_dev->name, IFNAMSIZ);
+		strscpy_pad(ifr.ifr_name, slave_dev->name, IFNAMSIZ);
 		mii = if_mii(&ifr);
 		if (ioctl(slave_dev, &ifr, SIOCGMIIPHY) == 0) {
 			mii->reg_num = MII_BMSR;
@@ -5330,10 +5330,8 @@ static int bond_check_params(struct bond_params *params)
 			(struct reciprocal_value) { 0 };
 	}
 
-	if (primary) {
-		strncpy(params->primary, primary, IFNAMSIZ);
-		params->primary[IFNAMSIZ - 1] = 0;
-	}
+	if (primary)
+		strscpy_pad(params->primary, primary, sizeof(params->primary));
 
 	memcpy(params->arp_targets, arp_target, sizeof(arp_target));
 

drivers/net/bonding/bond_options.c

@@ -1206,8 +1206,7 @@ static int bond_option_primary_set(struct bonding *bond,
 		RCU_INIT_POINTER(bond->primary_slave, NULL);
 		bond_select_active_slave(bond);
 	}
-	strncpy(bond->params.primary, primary, IFNAMSIZ);
-	bond->params.primary[IFNAMSIZ - 1] = 0;
+	strscpy_pad(bond->params.primary, primary, IFNAMSIZ);
 
 	netdev_dbg(bond->dev, "Recording %s as primary, but it has not been enslaved yet\n",
 		   primary);