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Commit 9f2e063d authored by Florian Westphal's avatar Florian Westphal Committed by Greg Kroah-Hartman
Browse files

netfilter: tproxy: fix deadlock due to missing BH disable 

[ Upstream commit 4a02426787bf024dafdb79b362285ee325de3f5e ]

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/401bd6ed-314a-a196-1cdc-e13c720cc8f2@balasys.hu/


Fixes: 4ed8eb65 ("netfilter: nf_tables: Add native tproxy support")
Reported-and-tested-by: default avatarMajor Dávid <major.david@balasys.hu>
Signed-off-by: default avatarFlorian Westphal <fw@strlen.de>
Signed-off-by: default avatarPablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent 16f3aae1

include/net/netfilter/nf_tproxy.h

+7 −0
Original line number Diff line number Diff line
@@ -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)

{

net/ipv4/netfilter/nf_tproxy_ipv4.c

+1 −1
Original line number Diff line number Diff line
@@ -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;

		}

	}

net/ipv6/netfilter/nf_tproxy_ipv6.c

+1 −1
Original line number Diff line number Diff line
@@ -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;

		}

	}