netfilter: nf_tables: fix false-positive lockdep splat

->abort invocation may cause splat on debug kernels:

WARNING: suspicious RCU usage
net/netfilter/nft_set_pipapo.c:1697 suspicious rcu_dereference_check() usage!
[..]
rcu_scheduler_active = 2, debug_locks = 1
1 lock held by nft/133554: [..] (nft_net->commit_mutex){+.+.}-{3:3}, at: nf_tables_valid_genid
[..]
 lockdep_rcu_suspicious+0x1ad/0x260
 nft_pipapo_abort+0x145/0x180
 __nf_tables_abort+0x5359/0x63d0
 nf_tables_abort+0x24/0x40
 nfnetlink_rcv+0x1a0a/0x22c0
 netlink_unicast+0x73c/0x900
 netlink_sendmsg+0x7f0/0xc20
 ____sys_sendmsg+0x48d/0x760

Transaction mutex is held, so parallel updates are not possible.
Switch to _protected and check mutex is held for lockdep enabled builds.

Fixes: 212ed75dc5fb ("netfilter: nf_tables: integrate pipapo into commit protocol")
Signed-off-by: Florian Westphal <fw@strlen.de>

diff --git a/net/netfilter/nft_set_pipapo.c b/net/netfilter/nft_set_pipapo.c
index a5b8301afe4aff1d48bc6880f3a684d9fcdec0e7..5fa12cfc7b844907af69bbc187ed9a1d3e3f272d 100644 (file)
--- a/net/netfilter/nft_set_pipapo.c
+++ b/net/netfilter/nft_set_pipapo.c
@@ -1697,6 +1697,17 @@ static void nft_pipapo_commit(const struct nft_set *set)
        priv->clone = new_clone;
 }
 
+static bool nft_pipapo_transaction_mutex_held(const struct nft_set *set)
+{
+#ifdef CONFIG_PROVE_LOCKING
+       const struct net *net = read_pnet(&set->net);
+
+       return lockdep_is_held(&nft_pernet(net)->commit_mutex);
+#else
+       return true;
+#endif
+}
+
 static void nft_pipapo_abort(const struct nft_set *set)
 {
        struct nft_pipapo *priv = nft_set_priv(set);
@@ -1705,7 +1716,7 @@ static void nft_pipapo_abort(const struct nft_set *set)
        if (!priv->dirty)
                return;
 
-       m = rcu_dereference(priv->match);
+       m = rcu_dereference_protected(priv->match, nft_pipapo_transaction_mutex_held(set));
 
        new_clone = pipapo_clone(m);
        if (IS_ERR(new_clone))