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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/401bd6ed-314a-a196-1cdc-e13c720cc8f2@balasys.hu/
Fixes: 4ed8eb6570 ("netfilter: nf_tables: Add native tproxy support")
Reported-and-tested-by: Major Dávid <major.david@balasys.hu>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Florian Westphal 2023-03-03 10:58:56 +01:00 committed by Pablo Neira Ayuso
parent 9f7dd42f0d
commit 4a02426787
3 changed files with 9 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
include/net/netfilter/nf_tproxy.h
View File

@ -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)
{

2
net/ipv4/netfilter/nf_tproxy_ipv4.c
View File

@ -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;
}
}

2
net/ipv6/netfilter/nf_tproxy_ipv6.c
View File

@ -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;
}
}