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

[David Miller]

From: Alexey Dobriyan 
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 

Applied to net-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   14441449  +5
team_nl_cmd_options_set  997 995  -2
tcf_em_tree_validate 872 870  -2
switchdev_port_bridge_setlink352 350  -2
switchdev_port_br_afspec 312 310  -2
rtm_to_fib_config428 426  -2
qla4xxx_sysfs_ddb_set_param 21932191  -2
qla4xxx_iface_set_param 44704468  -2
ovs_nla_free_flow_actions152 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  34163408  -8
netlbl_cipsov4_add_std  16721659 -13
nl80211_parse_sched_scan29022888 -14
nl80211_trigger_scan17381720 -18
do_execute_actions  28212738 -83
Total: Before=154865355, After=154865051, chg -0.00%

Signed-off-by: Alexey Dobriyan 
---

 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);