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Message-Id: <20250522165238.378456-10-pablo@netfilter.org>
Date: Thu, 22 May 2025 18:52:21 +0200
From: Pablo Neira Ayuso <pablo@...filter.org>
To: netfilter-devel@...r.kernel.org
Cc: davem@...emloft.net,
netdev@...r.kernel.org,
kuba@...nel.org,
pabeni@...hat.com,
edumazet@...gle.com,
fw@...len.de,
horms@...nel.org
Subject: [PATCH net-next 09/26] netfilter: nf_dup{4, 6}: Move duplication check to task_struct
From: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
nf_skb_duplicated is a per-CPU variable and relies on disabled BH for its
locking. Without per-CPU locking in local_bh_disable() on PREEMPT_RT
this data structure requires explicit locking.
Due to the recursion involved, the simplest change is to make it a
per-task variable.
Move the per-CPU variable nf_skb_duplicated to task_struct and name it
in_nf_duplicate. Add it to the existing bitfield so it doesn't use
additional memory.
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Juri Lelli <juri.lelli@...hat.com>
Cc: Vincent Guittot <vincent.guittot@...aro.org>
Cc: Dietmar Eggemann <dietmar.eggemann@....com>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Ben Segall <bsegall@...gle.com>
Cc: Mel Gorman <mgorman@...e.de>
Cc: Valentin Schneider <vschneid@...hat.com>
Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Signed-off-by: Pablo Neira Ayuso <pablo@...filter.org>
---
include/linux/netfilter.h | 11 -----------
include/linux/sched.h | 1 +
net/ipv4/netfilter/ip_tables.c | 2 +-
net/ipv4/netfilter/nf_dup_ipv4.c | 6 +++---
net/ipv6/netfilter/ip6_tables.c | 2 +-
net/ipv6/netfilter/nf_dup_ipv6.c | 6 +++---
net/netfilter/core.c | 3 ---
7 files changed, 9 insertions(+), 22 deletions(-)
diff --git a/include/linux/netfilter.h b/include/linux/netfilter.h
index 2b8aac2c70ad..892d12823ed4 100644
--- a/include/linux/netfilter.h
+++ b/include/linux/netfilter.h
@@ -497,17 +497,6 @@ struct nf_defrag_hook {
extern const struct nf_defrag_hook __rcu *nf_defrag_v4_hook;
extern const struct nf_defrag_hook __rcu *nf_defrag_v6_hook;
-/*
- * nf_skb_duplicated - TEE target has sent a packet
- *
- * When a xtables target sends a packet, the OUTPUT and POSTROUTING
- * hooks are traversed again, i.e. nft and xtables are invoked recursively.
- *
- * This is used by xtables TEE target to prevent the duplicated skb from
- * being duplicated again.
- */
-DECLARE_PER_CPU(bool, nf_skb_duplicated);
-
/*
* Contains bitmask of ctnetlink event subscribers, if any.
* Can't be pernet due to NETLINK_LISTEN_ALL_NSID setsockopt flag.
diff --git a/include/linux/sched.h b/include/linux/sched.h
index f96ac1982893..52d9c52dc8f2 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1044,6 +1044,7 @@ struct task_struct {
/* delay due to memory thrashing */
unsigned in_thrashing:1;
#endif
+ unsigned in_nf_duplicate:1;
#ifdef CONFIG_PREEMPT_RT
struct netdev_xmit net_xmit;
#endif
diff --git a/net/ipv4/netfilter/ip_tables.c b/net/ipv4/netfilter/ip_tables.c
index 3d101613f27f..23c8deff8095 100644
--- a/net/ipv4/netfilter/ip_tables.c
+++ b/net/ipv4/netfilter/ip_tables.c
@@ -270,7 +270,7 @@ ipt_do_table(void *priv,
* but it is no problem since absolute verdict is issued by these.
*/
if (static_key_false(&xt_tee_enabled))
- jumpstack += private->stacksize * __this_cpu_read(nf_skb_duplicated);
+ jumpstack += private->stacksize * current->in_nf_duplicate;
e = get_entry(table_base, private->hook_entry[hook]);
diff --git a/net/ipv4/netfilter/nf_dup_ipv4.c b/net/ipv4/netfilter/nf_dup_ipv4.c
index 25e1e8eb18dd..ed08fb78cfa8 100644
--- a/net/ipv4/netfilter/nf_dup_ipv4.c
+++ b/net/ipv4/netfilter/nf_dup_ipv4.c
@@ -54,7 +54,7 @@ void nf_dup_ipv4(struct net *net, struct sk_buff *skb, unsigned int hooknum,
struct iphdr *iph;
local_bh_disable();
- if (this_cpu_read(nf_skb_duplicated))
+ if (current->in_nf_duplicate)
goto out;
/*
* Copy the skb, and route the copy. Will later return %XT_CONTINUE for
@@ -86,9 +86,9 @@ void nf_dup_ipv4(struct net *net, struct sk_buff *skb, unsigned int hooknum,
--iph->ttl;
if (nf_dup_ipv4_route(net, skb, gw, oif)) {
- __this_cpu_write(nf_skb_duplicated, true);
+ current->in_nf_duplicate = true;
ip_local_out(net, skb->sk, skb);
- __this_cpu_write(nf_skb_duplicated, false);
+ current->in_nf_duplicate = false;
} else {
kfree_skb(skb);
}
diff --git a/net/ipv6/netfilter/ip6_tables.c b/net/ipv6/netfilter/ip6_tables.c
index 7d5602950ae7..d585ac3c1113 100644
--- a/net/ipv6/netfilter/ip6_tables.c
+++ b/net/ipv6/netfilter/ip6_tables.c
@@ -292,7 +292,7 @@ ip6t_do_table(void *priv, struct sk_buff *skb,
* but it is no problem since absolute verdict is issued by these.
*/
if (static_key_false(&xt_tee_enabled))
- jumpstack += private->stacksize * __this_cpu_read(nf_skb_duplicated);
+ jumpstack += private->stacksize * current->in_nf_duplicate;
e = get_entry(table_base, private->hook_entry[hook]);
diff --git a/net/ipv6/netfilter/nf_dup_ipv6.c b/net/ipv6/netfilter/nf_dup_ipv6.c
index 0c39c77fe8a8..b903c62c00c9 100644
--- a/net/ipv6/netfilter/nf_dup_ipv6.c
+++ b/net/ipv6/netfilter/nf_dup_ipv6.c
@@ -48,7 +48,7 @@ void nf_dup_ipv6(struct net *net, struct sk_buff *skb, unsigned int hooknum,
const struct in6_addr *gw, int oif)
{
local_bh_disable();
- if (this_cpu_read(nf_skb_duplicated))
+ if (current->in_nf_duplicate)
goto out;
skb = pskb_copy(skb, GFP_ATOMIC);
if (skb == NULL)
@@ -64,9 +64,9 @@ void nf_dup_ipv6(struct net *net, struct sk_buff *skb, unsigned int hooknum,
--iph->hop_limit;
}
if (nf_dup_ipv6_route(net, skb, gw, oif)) {
- __this_cpu_write(nf_skb_duplicated, true);
+ current->in_nf_duplicate = true;
ip6_local_out(net, skb->sk, skb);
- __this_cpu_write(nf_skb_duplicated, false);
+ current->in_nf_duplicate = false;
} else {
kfree_skb(skb);
}
diff --git a/net/netfilter/core.c b/net/netfilter/core.c
index b9f551f02c81..11a702065bab 100644
--- a/net/netfilter/core.c
+++ b/net/netfilter/core.c
@@ -31,9 +31,6 @@
const struct nf_ipv6_ops __rcu *nf_ipv6_ops __read_mostly;
EXPORT_SYMBOL_GPL(nf_ipv6_ops);
-DEFINE_PER_CPU(bool, nf_skb_duplicated);
-EXPORT_SYMBOL_GPL(nf_skb_duplicated);
-
#ifdef CONFIG_JUMP_LABEL
struct static_key nf_hooks_needed[NFPROTO_NUMPROTO][NF_MAX_HOOKS];
EXPORT_SYMBOL(nf_hooks_needed);
--
2.30.2
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