net_sched: act_skbmod: use RCU in tcf_skbmod_dump()

Also storing tcf_action into struct tcf_skbmod_params
makes sure there is no discrepancy in tcf_skbmod_act().

No longer block BH in tcf_skbmod_init() when acquiring tcf_lock.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20250827125349.3505302-5-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/include/net/tc_act/tc_skbmod.h b/include/net/tc_act/tc_skbmod.h
index 7c240d2fed4e3cdf686016588cd78eb52b80765b..626704cd6241b37f20539f9dd1270275ba19e578 100644 (file)
--- a/include/net/tc_act/tc_skbmod.h
+++ b/include/net/tc_act/tc_skbmod.h
@@ -12,6 +12,7 @@
 struct tcf_skbmod_params {
        struct rcu_head rcu;
        u64     flags; /*up to 64 types of operations; extend if needed */
+       int     action;
        u8      eth_dst[ETH_ALEN];
        u16     eth_type;
        u8      eth_src[ETH_ALEN];

diff --git a/net/sched/act_skbmod.c b/net/sched/act_skbmod.c
index dc022969346188c17a43f3ef40f3c203272954c4..fce625eafcb2b793cba7bebb740b136bf8498aa1 100644 (file)
--- a/net/sched/act_skbmod.c
+++ b/net/sched/act_skbmod.c
@@ -27,19 +27,18 @@ TC_INDIRECT_SCOPE int tcf_skbmod_act(struct sk_buff *skb,
                                     struct tcf_result *res)
 {
        struct tcf_skbmod *d = to_skbmod(a);
-       int action, max_edit_len, err;
        struct tcf_skbmod_params *p;
+       int max_edit_len, err;
        u64 flags;
 
        tcf_lastuse_update(&d->tcf_tm);
        bstats_update(this_cpu_ptr(d->common.cpu_bstats), skb);
 
-       action = READ_ONCE(d->tcf_action);
-       if (unlikely(action == TC_ACT_SHOT))
+       p = rcu_dereference_bh(d->skbmod_p);
+       if (unlikely(p->action == TC_ACT_SHOT))
                goto drop;
 
        max_edit_len = skb_mac_header_len(skb);
-       p = rcu_dereference_bh(d->skbmod_p);
        flags = p->flags;
 
        /* tcf_skbmod_init() guarantees "flags" to be one of the following:
@@ -85,7 +84,7 @@ TC_INDIRECT_SCOPE int tcf_skbmod_act(struct sk_buff *skb,
                INET_ECN_set_ce(skb);
 
 out:
-       return action;
+       return p->action;
 
 drop:
        qstats_overlimit_inc(this_cpu_ptr(d->common.cpu_qstats));
@@ -193,9 +192,9 @@ static int tcf_skbmod_init(struct net *net, struct nlattr *nla,
        }
 
        p->flags = lflags;
-
+       p->action = parm->action;
        if (ovr)
-               spin_lock_bh(&d->tcf_lock);
+               spin_lock(&d->tcf_lock);
        /* Protected by tcf_lock if overwriting existing action. */
        goto_ch = tcf_action_set_ctrlact(*a, parm->action, goto_ch);
        p_old = rcu_dereference_protected(d->skbmod_p, 1);
@@ -209,7 +208,7 @@ static int tcf_skbmod_init(struct net *net, struct nlattr *nla,
 
        rcu_assign_pointer(d->skbmod_p, p);
        if (ovr)
-               spin_unlock_bh(&d->tcf_lock);
+               spin_unlock(&d->tcf_lock);
 
        if (p_old)
                kfree_rcu(p_old, rcu);
@@ -248,10 +247,9 @@ static int tcf_skbmod_dump(struct sk_buff *skb, struct tc_action *a,
        opt.index   = d->tcf_index;
        opt.refcnt  = refcount_read(&d->tcf_refcnt) - ref;
        opt.bindcnt = atomic_read(&d->tcf_bindcnt) - bind;
-       spin_lock_bh(&d->tcf_lock);
-       opt.action = d->tcf_action;
-       p = rcu_dereference_protected(d->skbmod_p,
-                                     lockdep_is_held(&d->tcf_lock));
+       rcu_read_lock();
+       p = rcu_dereference(d->skbmod_p);
+       opt.action = p->action;
        opt.flags  = p->flags;
        if (nla_put(skb, TCA_SKBMOD_PARMS, sizeof(opt), &opt))
                goto nla_put_failure;
@@ -269,10 +267,10 @@ static int tcf_skbmod_dump(struct sk_buff *skb, struct tc_action *a,
        if (nla_put_64bit(skb, TCA_SKBMOD_TM, sizeof(t), &t, TCA_SKBMOD_PAD))
                goto nla_put_failure;
 
-       spin_unlock_bh(&d->tcf_lock);
+       rcu_read_unlock();
        return skb->len;
 nla_put_failure:
-       spin_unlock_bh(&d->tcf_lock);
+       rcu_read_unlock();
        nlmsg_trim(skb, b);
        return -1;
 }