From: Liping Zhang <zlpnobody@xxxxxxxxx>
We cannot setup nat info if the ct has been confirmed already, else,
different cpu may race to handle the same ct. In extreme situation,
we may hit the "BUG_ON(nf_nat_initialized(ct, maniptype))" in the
nf_nat_setup_info.
Also running the following commands will easily hit NF_CT_ASSERT in
nf_conntrack_alter_reply:
# nft flush ruleset
# ping -c 2 -W 1 1.1.1.111 &
# nft add table t
# nft add chain t c {type nat hook postrouting priority 0 \;}
# nft add rule t c snat to 4.5.6.7
WARNING: CPU: 1 PID: 10065 at net/netfilter/nf_conntrack_core.c:1472
nf_conntrack_alter_reply+0x9a/0x1a0 [nf_conntrack]
[...]
Call Trace:
nf_nat_setup_info+0xad/0x840 [nf_nat]
? deactivate_slab+0x65d/0x6c0
nft_nat_eval+0xcd/0x100 [nft_nat]
nft_do_chain+0xff/0x5d0 [nf_tables]
? mark_held_locks+0x6f/0xa0
? __local_bh_enable_ip+0x70/0xa0
? trace_hardirqs_on_caller+0x11f/0x190
? ipt_do_table+0x310/0x610
? trace_hardirqs_on+0xd/0x10
? __local_bh_enable_ip+0x70/0xa0
? ipt_do_table+0x32b/0x610
? __lock_acquire+0x2ac/0x1580
? ipt_do_table+0x32b/0x610
nft_nat_do_chain+0x65/0x80 [nft_chain_nat_ipv4]
nf_nat_ipv4_fn+0x1ae/0x240 [nf_nat_ipv4]
nf_nat_ipv4_out+0x4a/0xf0 [nf_nat_ipv4]
nft_nat_ipv4_out+0x15/0x20 [nft_chain_nat_ipv4]
nf_hook_slow+0x2c/0xf0
ip_output+0x154/0x270
So for the confirmed ct, just ignore it and return NF_ACCEPT.
Fixes: 9a08ecfe74d7 ("netfilter: don't attach a nat extension by default")
Signed-off-by: Liping Zhang <zlpnobody@xxxxxxxxx>
---
net/netfilter/nf_nat_core.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/net/netfilter/nf_nat_core.c b/net/netfilter/nf_nat_core.c
index b48d6b5..ef0be32 100644
--- a/net/netfilter/nf_nat_core.c
+++ b/net/netfilter/nf_nat_core.c
@@ -409,6 +409,10 @@ nf_nat_setup_info(struct nf_conn *ct,
{
struct nf_conntrack_tuple curr_tuple, new_tuple;
+ /* Can't setup nat info for confirmed ct. */
+ if (nf_ct_is_confirmed(ct))
+ return NF_ACCEPT;
+
NF_CT_ASSERT(maniptype == NF_NAT_MANIP_SRC ||
maniptype == NF_NAT_MANIP_DST);
BUG_ON(nf_nat_initialized(ct, maniptype));
--
2.9.3
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