korg/linux
0
0
Fork 0
mirror of https://mirrors.bfsu.edu.cn/git/linux.git synced 2024-11-11 12:28:41 +08:00
Code Issues Packages Projects Releases Wiki Activity

netfilter: nft_last: avoid possible false sharing

Browse Source 
Use the idiom described in:

https://github.com/google/ktsan/wiki/READ_ONCE-and-WRITE_ONCE#it-may-improve-performance

Moreover, prevent a compiler optimization.

Fixes: 836382dc24 ("netfilter: nf_tables: add last expression")
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Pablo Neira Ayuso 2021-07-17 10:20:08 +02:00
parent 32c3973d80
commit 32953df7a6
1 changed files with 13 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

20
net/netfilter/nft_last.c
View File

@ -48,24 +48,30 @@ static void nft_last_eval(const struct nft_expr *expr,
{
struct nft_last_priv *priv = nft_expr_priv(expr);
priv->last_jiffies = jiffies;
priv->last_set = 1;
if (READ_ONCE(priv->last_jiffies) != jiffies)
WRITE_ONCE(priv->last_jiffies, jiffies);
if (READ_ONCE(priv->last_set) == 0)
WRITE_ONCE(priv->last_set, 1);
}
static int nft_last_dump(struct sk_buff *skb, const struct nft_expr *expr)
{
struct nft_last_priv *priv = nft_expr_priv(expr);
unsigned long last_jiffies = READ_ONCE(priv->last_jiffies);
u32 last_set = READ_ONCE(priv->last_set);
__be64 msecs;
if (time_before(jiffies, priv->last_jiffies))
priv->last_set = 0;
if (time_before(jiffies, last_jiffies)) {
WRITE_ONCE(priv->last_set, 0);
last_set = 0;
}
if (priv->last_set)
msecs = nf_jiffies64_to_msecs(jiffies - priv->last_jiffies);
if (last_set)
msecs = nf_jiffies64_to_msecs(jiffies - last_jiffies);
else
msecs = 0;
if (nla_put_be32(skb, NFTA_LAST_SET, htonl(priv->last_set)) ||
if (nla_put_be32(skb, NFTA_LAST_SET, htonl(last_set)) ||
nla_put_be64(skb, NFTA_LAST_MSECS, msecs, NFTA_LAST_PAD))
goto nla_put_failure;