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netfilter: nf_dup{4, 6}: Move duplication check to task_struct

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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@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Ben Segall <bsegall@google.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Valentin Schneider <vschneid@redhat.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Sebastian Andrzej Siewior
2025-05-12 12:28:44 +02:00
committed by Pablo Neira Ayuso
parent 22a9613de4
commit a1f1acb9c5
7 changed files with 9 additions and 22 deletions
Download Patch File Download Diff File Expand all files Collapse all files

11
include/linux/netfilter.h
View File

@@ -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.

1
include/linux/sched.h
View File

@@ -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

2
net/ipv4/netfilter/ip_tables.c
View File

@@ -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]);

6
net/ipv4/netfilter/nf_dup_ipv4.c
View File

@@ -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);
}

2
net/ipv6/netfilter/ip6_tables.c
View File

@@ -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]);

6
net/ipv6/netfilter/nf_dup_ipv6.c
View File

@@ -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);
}

3
net/netfilter/core.c
View File

@@ -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);