netlink: use "unsigned int" in nla_next()

->nla_len is unsigned entity (it's length after all) and u16, thus it can't overflow when being aligned into int/unsigned int.

(nlmsg_next has the same code, but I didn't yet convince myself it is correct to do so).

There is pointer arithmetic in this function and offset being unsigned is better:

add/remove: 0/0 grow/shrink: 1/64 up/down: 5/-309 (-304)
function old new delta
nl80211_set_wiphy 1444 1449 +5
team_nl_cmd_options_set 997 995 -2
tcf_em_tree_validate 872 870 -2
switchdev_port_bridge_setlink 352 350 -2
switchdev_port_br_afspec 312 310 -2
rtm_to_fib_config 428 426 -2
qla4xxx_sysfs_ddb_set_param 2193 2191 -2
qla4xxx_iface_set_param 4470 4468 -2
ovs_nla_free_flow_actions 152 150 -2
output_userspace 518 516 -2
...
nl80211_set_reg 654 649 -5
validate_scan_freqs 148 142 -6
validate_linkmsg 288 282 -6
nl80211_parse_connkeys 489 483 -6
nlattr_set 231 224 -7
nf_tables_delsetelem 267 260 -7
do_setlink 3416 3408 -8
netlbl_cipsov4_add_std 1672 1659 -13
nl80211_parse_sched_scan 2902 2888 -14
nl80211_trigger_scan 1738 1720 -18
do_execute_actions 2821 2738 -83
Total: Before=154865355, After=154865051, chg -0.00%

---

 include/net/netlink.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

@@ -713,7 +713,7 @@ static inline bool nla_ok(const struct nlattr *nla, int remaining)
  */
 static inline struct nlattr *nla_next(const struct nlattr *nla, int *remaining)
 {
-	int totlen = NLA_ALIGN(nla->nla_len);
+	unsigned int totlen = NLA_ALIGN(nla->nla_len);
 
 	*remaining -= totlen;
 	return (struct nlattr *) ((char *) nla + totlen);

From: Alexey Dobriyan <[email protected]>
Date: Sat, 19 Nov 2016 03:54:35 +0300

...

Applied to net-next.