[PATCH] netlink: use "unsigned int" in nla_next()

[PATCH] netlink: use "unsigned int" in nla_next()

[Alexey Dobriyan]

->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%

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
---

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

--- a/include/net/netlink.h
+++ b/include/net/netlink.h
@@ -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);

Re: [PATCH] netlink: use "unsigned int" in nla_next()

[David Miller]

From: Alexey Dobriyan <adobriyan@gmail.com>
Date: Sat, 19 Nov 2016 03:54:35 +0300

> ->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:
 ...
> Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>

Applied to net-next.