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Florian Westphal 50d9ce9679 netfilter: nf_nat: also check reverse tuple to obtain clashing entry 
The logic added in the blamed commit was supposed to only omit nat source
port allocation if neither the existing nor the new entry are subject to
NAT.

However, its not enough to lookup the conntrack based on the proposed
tuple, we must also check the reverse direction.

Otherwise there are esoteric cases where the collision is in the reverse
direction because that colliding connection has a port rewrite, but the
new entry doesn't.  In this case, we only check the new entry and then
erronously conclude that no clash exists anymore.

 The existing (udp) tuple is:
  a:p -> b:P, with nat translation to s:P, i.e. pure daddr rewrite,
  reverse tuple in conntrack table is s:P -> a:p.

When another UDP packet is sent directly to s, i.e. a:p->s:P, this is
correctly detected as a colliding entry: tuple is taken by existing reply
tuple in reverse direction.

But the colliding conntrack is only searched for with unreversed
direction, and we can't find such entry matching a:p->s:P.

The incorrect conclusion is that the clashing entry has timed out and
that no port address translation is required.

Such conntrack will then be discarded at nf_confirm time because the
proposed reverse direction clashes with an existing mapping in the
conntrack table.

Search for the reverse tuple too, this will then check the NAT bits of
the colliding entry and triggers port reallocation.

Followp patch extends nft_nat.sh selftest to cover this scenario.

The IPS_SEQ_ADJUST change is also a bug fix:
Instead of checking for SEQ_ADJ this tested for SEEN_REPLY and ASSURED
by accident -- _BIT is only for use with the test_bit() API.

This bug has little consequence in practice, because the sequence number
adjustments are only useful for TCP which doesn't support clash resolution.

The existing test case (conntrack_reverse_clash.sh) exercise a race
condition path (parallel conntrack creation on different CPUs), so
the colliding entries have neither SEEN_REPLY nor ASSURED set.

Thanks to Yafang Shao and Shaun Brady for an initial investigation
of this bug.

Fixes: d8f84a9bc7 ("netfilter: nf_nat: don't try nat source port reallocation for reverse dir clash")
Closes: https://bugzilla.netfilter.org/show_bug.cgi?id=1795
Reported-by: Yafang Shao <laoar.shao@gmail.com>
Reported-by: Shaun Brady <brady.1345@gmail.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
Tested-by: Yafang Shao <laoar.shao@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
2025-06-05 10:50:05 +02:00
..
ipset netfilter: ipset: fix region locking in hash types 2025-05-07 23:57:31 +02:00
ipvs sctp: use skb_crc32c() instead of __skb_checksum() 2025-05-21 15:40:16 -07:00
core.c netfilter: nf_dup{4, 6}: Move duplication check to task_struct 2025-05-23 13:57:12 +02:00
Kconfig sctp: use skb_crc32c() instead of __skb_checksum() 2025-05-21 15:40:16 -07:00
Makefile netfilter: Add bpf_xdp_flow_lookup kfunc 2024-07-01 17:03:01 +02:00
nf_bpf_link.c netfilter: bpf: Pass string literal as format argument of request_module() 2024-11-14 12:39:50 +01:00
nf_conncount.c netfilter: nf_conncount: Fully initialize struct nf_conncount_tuple in insert_tree() 2025-03-12 15:28:33 +01:00
nf_conntrack_acct.c
nf_conntrack_amanda.c netfilter: conntrack: remove skb argument from nf_ct_refresh 2025-01-19 16:41:55 +01:00
nf_conntrack_bpf.c net: netfilter: Make ct zone opts configurable for bpf ct helpers 2024-05-22 15:00:56 -07:00
nf_conntrack_broadcast.c netfilter: conntrack: remove skb argument from nf_ct_refresh 2025-01-19 16:41:55 +01:00
nf_conntrack_core.c netfilter: conntrack: make nf_conntrack_id callable without a module dependency 2025-05-23 13:57:12 +02:00
nf_conntrack_ecache.c netfilter: conntrack: add conntrack event timestamp 2025-01-09 14:42:16 +01:00
nf_conntrack_expect.c treewide: Switch/rename to timer_delete[_sync]() 2025-04-05 10:30:12 +02:00
nf_conntrack_extend.c netfilter: conntrack: fix extension size table 2023-09-13 21:57:50 +02:00
nf_conntrack_ftp.c
nf_conntrack_h323_asn1.c netfilter: nf_conntrack_h323: Add protection for bmp length out of range 2024-03-07 03:10:35 +01:00
nf_conntrack_h323_main.c netfilter: conntrack: remove skb argument from nf_ct_refresh 2025-01-19 16:41:55 +01:00
nf_conntrack_h323_types.c
nf_conntrack_helper.c netfilter: conntrack: simplify nf_conntrack_alter_reply 2023-10-10 16:34:28 +02:00
nf_conntrack_irc.c
nf_conntrack_labels.c netfilter: conntrack: switch connlabels to atomic_t 2023-10-24 13:16:30 +02:00
nf_conntrack_netbios_ns.c
nf_conntrack_netlink.c treewide: Switch/rename to timer_delete[_sync]() 2025-04-05 10:30:12 +02:00
nf_conntrack_ovs.c
nf_conntrack_pptp.c
nf_conntrack_proto.c netfilter: add missing module descriptions 2023-11-08 13:52:32 +01:00
nf_conntrack_proto_dccp.c netfilter: conntrack: dccp: try not to drop skb in conntrack 2024-05-06 11:13:56 +02:00
nf_conntrack_proto_generic.c
nf_conntrack_proto_gre.c
nf_conntrack_proto_icmp.c
nf_conntrack_proto_icmpv6.c netfilter: conntrack: fix ct-state for ICMPv6 Multicast Router Discovery 2024-05-06 11:13:56 +02:00
nf_conntrack_proto_sctp.c netfilter: conntrack: cleanup timeout definitions 2025-01-12 20:21:01 -08:00
nf_conntrack_proto_tcp.c move asm/unaligned.h to linux/unaligned.h 2024-10-02 17:23:23 -04:00
nf_conntrack_proto_udp.c
nf_conntrack_sane.c
nf_conntrack_seqadj.c
nf_conntrack_sip.c netfilter: conntrack: remove skb argument from nf_ct_refresh 2025-01-19 16:41:55 +01:00
nf_conntrack_snmp.c
nf_conntrack_standalone.c netfilter: nf_conntrack: speed up reads from nf_conntrack proc file 2025-05-05 13:16:26 +02:00
nf_conntrack_tftp.c
nf_conntrack_timeout.c
nf_conntrack_timestamp.c
nf_dup_netdev.c netfilter: nf_dup_netdev: Move the recursion counter struct netdev_xmit 2025-05-23 13:57:12 +02:00
nf_flow_table_bpf.c netfilter: Add bpf_xdp_flow_lookup kfunc 2024-07-01 17:03:01 +02:00
nf_flow_table_core.c netfilter: conntrack: fix erronous removal of offload bit 2025-04-17 11:14:22 +02:00
nf_flow_table_inet.c net: netfilter: move nf flowtable bpf initialization in nf_flow_table_module_init() 2024-09-12 15:41:03 +02:00
nf_flow_table_ip.c Revert "netfilter: flowtable: teardown flow if cached mtu is stale" 2025-02-12 10:35:20 +01:00
nf_flow_table_offload.c net: hold netdev instance lock during nft ndo_setup_tc 2025-03-06 12:59:43 -08:00
nf_flow_table_procfs.c
nf_flow_table_xdp.c netfilter: nf_tables: Add flowtable map for xdp offload 2024-07-01 17:01:53 +02:00
nf_hooks_lwtunnel.c sysctl: treewide: constify the ctl_table argument of proc_handlers 2024-07-24 20:59:29 +02:00
nf_internals.h netfilter: move the sysctl nf_hooks_lwtunnel into the netfilter core 2024-06-19 18:41:59 +02:00
nf_log.c sysctl: treewide: constify the ctl_table argument of proc_handlers 2024-07-24 20:59:29 +02:00
nf_log_syslog.c tcp: extend TCP flags to allow AE bit/ACE field 2025-03-17 13:49:46 +00:00
nf_nat_amanda.c
nf_nat_bpf.c bpf: treewide: Annotate BPF kfuncs in BTF 2024-01-31 20:40:56 -08:00
nf_nat_core.c netfilter: nf_nat: also check reverse tuple to obtain clashing entry 2025-06-05 10:50:05 +02:00
nf_nat_ftp.c
nf_nat_helper.c
nf_nat_irc.c
nf_nat_masquerade.c
nf_nat_ovs.c netfilter: nf_nat: fix action not being set for all ct states 2024-01-03 11:17:17 +01:00
nf_nat_proto.c ipsec-next-2023-10-28 2023-10-30 14:36:57 -07:00
nf_nat_redirect.c netfilter: nat: fix ipv6 nat redirect with mapped and scoped addresses 2023-11-08 16:40:30 +01:00
nf_nat_sip.c
nf_nat_tftp.c
nf_queue.c netfilter: move nf_reinject into nfnetlink_queue modules 2024-02-21 12:03:22 +01:00
nf_sockopt.c
nf_synproxy_core.c move asm/unaligned.h to linux/unaligned.h 2024-10-02 17:23:23 -04:00
nf_tables_api.c netfilter: nf_tables: Add notifications for hook changes 2025-05-23 13:57:14 +02:00
nf_tables_core.c netfilter: nf_tables: Only use nf_skip_indirect_calls() when MITIGATION_RETPOLINE 2025-03-23 10:53:47 +01:00
nf_tables_offload.c netfilter: nf_tables: Have a list of nf_hook_ops in nft_hook 2025-05-23 13:57:13 +02:00
nf_tables_trace.c netfilter: nf_tables: add packets conntrack state to debug trace info 2025-05-23 13:57:12 +02:00
nfnetlink.c netfilter: nf_tables: Add notifications for hook changes 2025-05-23 13:57:14 +02:00
nfnetlink_acct.c
nfnetlink_cthelper.c
nfnetlink_cttimeout.c netfilter: cttimeout: remove 'l3num' attr check 2024-06-26 00:54:53 +02:00
nfnetlink_hook.c
nfnetlink_log.c treewide: Switch/rename to timer_delete[_sync]() 2025-04-05 10:30:12 +02:00
nfnetlink_osf.c netfilter: add missing module descriptions 2023-11-08 13:52:32 +01:00
nfnetlink_queue.c netfilter: nfnetlink_queue: Initialize ctx to avoid memory allocation error 2025-03-23 10:20:33 +01:00
nft_bitwise.c netfilter: bitwise: add support for doing AND, OR and XOR directly 2024-11-15 12:07:04 +01:00
nft_byteorder.c move asm/unaligned.h to linux/unaligned.h 2024-10-02 17:23:23 -04:00
nft_chain_filter.c netfilter: nf_tables: Add notifications for hook changes 2025-05-23 13:57:14 +02:00
nft_chain_nat.c netfilter: add missing module descriptions 2023-11-08 13:52:32 +01:00
nft_chain_route.c
nft_cmp.c netfilter: nf_tables: pass context structure to nft_parse_register_load 2024-08-20 12:37:24 +02:00
nft_compat.c netfilter: nf_tables: make destruction work queue pernet 2025-03-06 13:35:54 +01:00
nft_connlimit.c netfilter: nf_tables: allow clone callbacks to sleep 2024-05-10 11:13:45 +02:00
nft_counter.c netfilter: nft_counter: Use u64_stats_t for statistic. 2024-09-03 10:47:16 +02:00
nft_ct.c netfilter: nft_ct: Use __refcount_inc() for per-CPU nft_ct_pcpu_template. 2025-03-03 13:46:49 +01:00
nft_ct_fast.c
nft_dup_netdev.c netfilter: nf_tables: pass context structure to nft_parse_register_load 2024-08-20 12:37:24 +02:00
nft_dynset.c netfilter: nf_tables: set element timeout update support 2024-09-03 18:19:44 +02:00
nft_exthdr.c netfilter: nft_exthdr: fix offset with ipv4_find_option() 2025-03-13 10:02:39 +01:00
nft_fib.c netfilter: nf_tables: drop unused 3rd argument from validate callback ops 2024-09-03 10:47:17 +02:00
nft_fib_inet.c
nft_fib_netdev.c
nft_flow_offload.c netfilter: nf_tables: Introduce nft_hook_find_ops{,_rcu}() 2025-05-23 13:57:12 +02:00
nft_fwd_netdev.c netfilter: nf_tables: drop unused 3rd argument from validate callback ops 2024-09-03 10:47:17 +02:00
nft_hash.c netfilter: nf_tables: pass context structure to nft_parse_register_load 2024-08-20 12:37:24 +02:00
nft_immediate.c netfilter: nf_tables: drop unused 3rd argument from validate callback ops 2024-09-03 10:47:17 +02:00
nft_inner.c netfilter: nft_inner: Use nested-BH locking for nft_pcpu_tun_ctx 2025-05-23 13:57:12 +02:00
nft_last.c netfilter: nf_tables: allow clone callbacks to sleep 2024-05-10 11:13:45 +02:00
nft_limit.c netfilter: nf_tables: allow clone callbacks to sleep 2024-05-10 11:13:45 +02:00
nft_log.c netfilter: nf_tables: missing objects with no memcg accounting 2024-09-26 13:03:02 +02:00
nft_lookup.c netfilter: nf_tables: drop unused 3rd argument from validate callback ops 2024-09-03 10:47:17 +02:00
nft_masq.c netfilter: nf_tables: drop unused 3rd argument from validate callback ops 2024-09-03 10:47:17 +02:00
nft_meta.c netfilter: nf_tables: missing objects with no memcg accounting 2024-09-26 13:03:02 +02:00
nft_nat.c netfilter: nf_tables: drop unused 3rd argument from validate callback ops 2024-09-03 10:47:17 +02:00
nft_numgen.c netfilter: nf_tables: missing objects with no memcg accounting 2024-09-26 13:03:02 +02:00
nft_objref.c netfilter: nf_tables: pass context structure to nft_parse_register_load 2024-08-20 12:37:24 +02:00
nft_osf.c netfilter: nf_tables: drop unused 3rd argument from validate callback ops 2024-09-03 10:47:17 +02:00
nft_payload.c netfilter: nft_payload: sanitize offset and length before calling skb_checksum() 2024-10-31 10:54:49 +01:00
nft_queue.c netfilter: nf_tables: drop unused 3rd argument from validate callback ops 2024-09-03 10:47:17 +02:00
nft_quota.c netfilter: nft_quota: match correctly when the quota just depleted 2025-05-05 13:15:09 +02:00
nft_range.c netfilter: nf_tables: pass context structure to nft_parse_register_load 2024-08-20 12:37:24 +02:00
nft_redir.c netfilter: nf_tables: drop unused 3rd argument from validate callback ops 2024-09-03 10:47:17 +02:00
nft_reject.c netfilter: nf_tables: drop unused 3rd argument from validate callback ops 2024-09-03 10:47:17 +02:00
nft_reject_inet.c netfilter: nf_tables: drop unused 3rd argument from validate callback ops 2024-09-03 10:47:17 +02:00
nft_reject_netdev.c netfilter: nf_tables: drop unused 3rd argument from validate callback ops 2024-09-03 10:47:17 +02:00
nft_rt.c netfilter: nf_tables: drop unused 3rd argument from validate callback ops 2024-09-03 10:47:17 +02:00
nft_set_bitmap.c netfilter: nf_tables: avoid false-positive lockdep splats in set walker 2024-11-05 22:06:22 +01:00
nft_set_hash.c netfilter: nft_set_hash: GC reaps elements with conncount for dynamic sets only 2025-04-02 22:50:56 +02:00
nft_set_pipapo.c netfilter: nft_set_pipapo: clamp maximum map bucket size to INT_MAX 2025-05-05 13:17:32 +02:00
nft_set_pipapo.h netfilter: nf_set_pipapo: fix initial map fill 2024-07-17 19:00:47 +02:00
nft_set_pipapo_avx2.c netfilter: nf_set_pipapo_avx2: fix initial map fill 2025-06-05 10:49:58 +02:00
nft_set_pipapo_avx2.h
nft_set_rbtree.c netfilter: nf_tables: fix set size with rbtree backend 2025-01-19 16:41:41 +01:00
nft_socket.c netfilter: nft_socket: remove WARN_ON_ONCE on maximum cgroup level 2024-11-28 13:14:24 +01:00
nft_synproxy.c netfilter: nf_tables: drop unused 3rd argument from validate callback ops 2024-09-03 10:47:17 +02:00
nft_tproxy.c netfilter: nf_tables: drop unused 3rd argument from validate callback ops 2024-09-03 10:47:17 +02:00
nft_tunnel.c netfilter: nft_tunnel: fix geneve_opt dump 2025-05-23 13:57:12 +02:00
nft_xfrm.c xfrm: add generic iptfs defines and functionality 2024-12-05 10:01:28 +01:00
utils.c netfilter: move nf_reinject into nfnetlink_queue modules 2024-02-21 12:03:22 +01:00
x_tables.c netfilter: Fix use-after-free in get_info() 2024-10-30 13:17:36 +01:00
xt_addrtype.c netfilter: xtables: avoid NFPROTO_UNSPEC where needed 2024-10-09 23:20:46 +02:00
xt_AUDIT.c
xt_bpf.c
xt_cgroup.c net: cgroup: Guard users of sock_cgroup_classid() 2025-04-24 16:04:02 +02:00
xt_CHECKSUM.c netfilter: xtables: avoid NFPROTO_UNSPEC where needed 2024-10-09 23:20:46 +02:00
xt_CLASSIFY.c netfilter: xtables: avoid NFPROTO_UNSPEC where needed 2024-10-09 23:20:46 +02:00
xt_cluster.c netfilter: xtables: avoid NFPROTO_UNSPEC where needed 2024-10-09 23:20:46 +02:00
xt_comment.c
xt_connbytes.c netfilter: xtables: avoid NFPROTO_UNSPEC where needed 2024-10-09 23:20:46 +02:00
xt_connlabel.c
xt_connlimit.c netfilter: xtables: avoid NFPROTO_UNSPEC where needed 2024-10-09 23:20:46 +02:00
xt_connmark.c netfilter: xtables: avoid NFPROTO_UNSPEC where needed 2024-10-09 23:20:46 +02:00
xt_CONNSECMARK.c netfilter: xtables: avoid NFPROTO_UNSPEC where needed 2024-10-09 23:20:46 +02:00
xt_conntrack.c
xt_cpu.c
xt_CT.c netfilter: xtables: avoid NFPROTO_UNSPEC where needed 2024-10-09 23:20:46 +02:00
xt_dccp.c
xt_devgroup.c
xt_dscp.c
xt_DSCP.c
xt_ecn.c
xt_esp.c
xt_hashlimit.c netfilter: xt_hashlimit: replace vmalloc calls with kvmalloc 2025-03-12 16:37:48 +01:00
xt_helper.c
xt_hl.c
xt_HL.c
xt_HMARK.c
xt_IDLETIMER.c netfilter: xt_IDLETIMER: convert timeouts to secs_to_jiffies() 2025-04-24 16:04:01 +02:00
xt_ipcomp.c
xt_iprange.c
xt_ipvs.c
xt_l2tp.c
xt_LED.c netfilter: x_tables: fix LED ID check in led_tg_check() 2024-11-28 13:14:24 +01:00
xt_length.c
xt_limit.c
xt_LOG.c
xt_mac.c
xt_mark.c netfilter: xtables: support arpt_mark and ipv6 optstrip for iptables-nft only builds 2025-05-22 17:16:02 +02:00
xt_MASQUERADE.c
xt_multiport.c
xt_nat.c
xt_NETMAP.c
xt_nfacct.c
xt_NFLOG.c netfilter: xtables: fix typo causing some targets not to load on IPv6 2024-10-21 11:31:26 +02:00
xt_NFQUEUE.c
xt_osf.c
xt_owner.c netfilter: xt_owner: Fix for unsafe access of sk->sk_socket 2023-12-06 17:52:15 +01:00
xt_physdev.c netfilter: propagate net to nf_bridge_get_physindev 2024-01-17 12:02:48 +01:00
xt_pkttype.c
xt_policy.c
xt_quota.c
xt_RATEEST.c netfilter: xtables: avoid NFPROTO_UNSPEC where needed 2024-10-09 23:20:46 +02:00
xt_rateest.c
xt_realm.c
xt_recent.c netfilter: xt_recent: Lift restrictions on max hitcount value 2024-06-28 17:57:50 +02:00
xt_REDIRECT.c
xt_repldata.h netfilter: xtables: Use strscpy() instead of strscpy_pad() 2025-03-23 10:53:47 +01:00
xt_sctp.c netfilter: xt_sctp: validate the flag_info count 2023-08-30 17:34:01 +02:00
xt_SECMARK.c netfilter: xtables: avoid NFPROTO_UNSPEC where needed 2024-10-09 23:20:46 +02:00
xt_set.c
xt_socket.c
xt_state.c
xt_statistic.c
xt_string.c
xt_TCPMSS.c
xt_tcpmss.c
xt_TCPOPTSTRIP.c netfilter: xtables: support arpt_mark and ipv6 optstrip for iptables-nft only builds 2025-05-22 17:16:02 +02:00
xt_tcpudp.c
xt_TEE.c
xt_time.c
xt_TPROXY.c
xt_TRACE.c netfilter: xtables: fix typo causing some targets not to load on IPv6 2024-10-21 11:31:26 +02:00
xt_u32.c netfilter: xt_u32: validate user space input 2023-08-30 17:34:01 +02:00