netfilter: tproxy: fix deadlock due to missing BH disable

The xtables packet traverser performs an unconditional local_bh_disable(), but the nf_tables evaluation loop does not. Functions that are called from either xtables or nftables must assume that they can be called in process context. inet_twsk_deschedule_put() assumes that no softirq interrupt can occur. If tproxy is used from nf_tables its possible that we'll deadlock trying to aquire a lock already held in process context. Add a small helper that takes care of this and use it. Link: https://lore.kernel.org/netfilter-devel/[email protected]/ Fixes: 4ed8eb6 ("netfilter: nf_tables: Add native tproxy support") Reported-and-tested-by: Major Dávid <[email protected]> Signed-off-by: Florian Westphal <[email protected]> Signed-off-by: Pablo Neira Ayuso <[email protected]>
sumirart · Mar 6, 2023 · 4a02426 · 4a02426
1 parent 9f7dd42
commit 4a02426
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Showing 3 changed files with 9 additions and 2 deletions.
diff --git a/include/net/netfilter/nf_tproxy.h b/include/net/netfilter/nf_tproxy.h
@@ -17,6 +17,13 @@ static inline bool nf_tproxy_sk_is_transparent(struct sock *sk)
 	return false;
 }
 
+static inline void nf_tproxy_twsk_deschedule_put(struct inet_timewait_sock *tw)
+{
+	local_bh_disable();
+	inet_twsk_deschedule_put(tw);
+	local_bh_enable();
+}
+
 /* assign a socket to the skb -- consumes sk */
 static inline void nf_tproxy_assign_sock(struct sk_buff *skb, struct sock *sk)
 {

diff --git a/net/ipv4/netfilter/nf_tproxy_ipv4.c b/net/ipv4/netfilter/nf_tproxy_ipv4.c
@@ -38,7 +38,7 @@ nf_tproxy_handle_time_wait4(struct net *net, struct sk_buff *skb,
 					    hp->source, lport ? lport : hp->dest,
 					    skb->dev, NF_TPROXY_LOOKUP_LISTENER);
 		if (sk2) {
-			inet_twsk_deschedule_put(inet_twsk(sk));
+			nf_tproxy_twsk_deschedule_put(inet_twsk(sk));
 			sk = sk2;
 		}
 	}

diff --git a/net/ipv6/netfilter/nf_tproxy_ipv6.c b/net/ipv6/netfilter/nf_tproxy_ipv6.c
@@ -63,7 +63,7 @@ nf_tproxy_handle_time_wait6(struct sk_buff *skb, int tproto, int thoff,
 					    lport ? lport : hp->dest,
 					    skb->dev, NF_TPROXY_LOOKUP_LISTENER);
 		if (sk2) {
-			inet_twsk_deschedule_put(inet_twsk(sk));
+			nf_tproxy_twsk_deschedule_put(inet_twsk(sk));
 			sk = sk2;
 		}
 	}