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linux/net/ipv4
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Chuang Wang 298f1e0694 ipv4: route: Prevent rt_bind_exception() from rebinding stale fnhe 
commit ac1499fcd4 upstream.

The sit driver's packet transmission path calls: sit_tunnel_xmit() ->
update_or_create_fnhe(), which lead to fnhe_remove_oldest() being called
to delete entries exceeding FNHE_RECLAIM_DEPTH+random.

The race window is between fnhe_remove_oldest() selecting fnheX for
deletion and the subsequent kfree_rcu(). During this time, the
concurrent path's __mkroute_output() -> find_exception() can fetch the
soon-to-be-deleted fnheX, and rt_bind_exception() then binds it with a
new dst using a dst_hold(). When the original fnheX is freed via RCU,
the dst reference remains permanently leaked.

CPU 0                             CPU 1
__mkroute_output()
  find_exception() [fnheX]
                                  update_or_create_fnhe()
                                    fnhe_remove_oldest() [fnheX]
  rt_bind_exception() [bind dst]
                                  RCU callback [fnheX freed, dst leak]

This issue manifests as a device reference count leak and a warning in
dmesg when unregistering the net device:

  unregister_netdevice: waiting for sitX to become free. Usage count = N

Ido Schimmel provided the simple test validation method [1].

The fix clears 'oldest->fnhe_daddr' before calling fnhe_flush_routes().
Since rt_bind_exception() checks this field, setting it to zero prevents
the stale fnhe from being reused and bound to a new dst just before it
is freed.

[1]
ip netns add ns1
ip -n ns1 link set dev lo up
ip -n ns1 address add 192.0.2.1/32 dev lo
ip -n ns1 link add name dummy1 up type dummy
ip -n ns1 route add 192.0.2.2/32 dev dummy1
ip -n ns1 link add name gretap1 up arp off type gretap \
    local 192.0.2.1 remote 192.0.2.2
ip -n ns1 route add 198.51.0.0/16 dev gretap1
taskset -c 0 ip netns exec ns1 mausezahn gretap1 \
    -A 198.51.100.1 -B 198.51.0.0/16 -t udp -p 1000 -c 0 -q &
taskset -c 2 ip netns exec ns1 mausezahn gretap1 \
    -A 198.51.100.1 -B 198.51.0.0/16 -t udp -p 1000 -c 0 -q &
sleep 10
ip netns pids ns1 | xargs kill
ip netns del ns1

Cc: stable@vger.kernel.org
Fixes: 67d6d681e1 ("ipv4: make exception cache less predictible")
Signed-off-by: Chuang Wang <nashuiliang@gmail.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20251111064328.24440-1-nashuiliang@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2025-12-07 06:09:29 +09:00
..
bpfilter net: Revert "net: optimize the sockptr_t for unified kernel/user address spaces" 2020-08-10 12:06:44 -07:00
netfilter netfilter: nf_reject: don't reply to icmp error messages 2025-12-07 06:09:21 +09:00
af_inet.c net: inet: do not leave a dangling sk pointer in inet_create() 2024-12-14 19:51:37 +01:00
ah4.c Networking changes for 5.14. 2021-06-30 15:51:09 -07:00
arp.c arp: switch to dev_getbyhwaddr() in arp_req_set_public() 2025-03-13 12:50:53 +01:00
bpf_tcp_ca.c bpf: Forbid bpf_ktime_get_coarse_ns and bpf_timer_* in tracing progs 2021-11-25 09:49:07 +01:00
cipso_ipv4.c cipso: fix total option length computation 2024-07-05 09:14:29 +02:00
datagram.c udp: Update reuse->has_conns under reuseport_lock. 2022-10-29 10:12:56 +02:00
devinet.c ipv4: Fix NULL vs error pointer check in inet_blackhole_dev_init() 2025-09-09 18:50:19 +02:00
esp4.c net: esp: cleanup esp_output_tail_tcp() in case of unsupported ESPINTCP 2024-08-19 05:44:55 +02:00
esp4_offload.c xfrm: Linearize the skb after offloading if needed. 2023-06-28 10:29:46 +02:00
fib_frontend.c ipv4: fib: Move fib_valid_key_len() to rtm_to_fib_config(). 2025-06-04 14:37:59 +02:00
fib_lookup.h ipv4: fix data races in fib_alias_hw_flags_set 2022-02-23 12:03:10 +01:00
fib_notifier.c net: fib_notifier: propagate extack down to the notifier block callback 2019-10-04 11:10:56 -07:00
fib_rules.c ip: fib_rules: Fetch net from fib_rule in fib[46]_rule_configure(). 2025-06-04 14:38:03 +02:00
fib_semantics.c net: Add l3mdev index to flow struct and avoid oif reset for port devices 2024-10-17 15:11:57 +02:00
fib_trie.c ipv4: fib: Move fib_valid_key_len() to rtm_to_fib_config(). 2025-06-04 14:37:59 +02:00
fou.c fou: remove warn in gue_gro_receive on unsupported protocol 2024-12-14 19:51:46 +01:00
gre_demux.c net: Remove the member netns_ok 2021-05-17 15:29:35 -07:00
gre_offload.c gro: remove rcu_read_lock/rcu_read_unlock from gro_complete handlers 2024-09-12 11:07:47 +02:00
icmp.c icmp: fix icmp_ndo_send address translation for reply direction 2025-09-09 18:50:18 +02:00
igmp.c bpf: net: Change do_ip_getsockopt() to take the sockptr_t argument 2024-03-26 18:21:23 -04:00
inet_connection_sock.c tcp: Fix use-after-free of nreq in reqsk_timer_handler(). 2024-12-14 19:51:10 +01:00
inet_diag.c inet_diag: Initialize pad field in struct inet_diag_req_v2 2024-07-18 13:07:31 +02:00
inet_fragment.c inet: inet_defrag: prevent sk release while still in use 2024-10-17 15:10:41 +02:00
inet_hashtables.c tcp: bring back NUMA dispersion in inet_ehash_locks_alloc() 2025-06-04 14:37:58 +02:00
inet_timewait_sock.c tcp: Fix NEW_SYN_RECV handling in inet_twsk_purge() 2024-05-02 16:24:49 +02:00
inetpeer.c inetpeer: Fix data-races around sysctl. 2022-07-21 21:24:21 +02:00
ip_forward.c ip: Fix data-races around sysctl_ip_fwd_update_priority. 2022-07-29 17:25:13 +02:00
ip_fragment.c inet: inet_defrag: prevent sk release while still in use 2024-10-17 15:10:41 +02:00
ip_gre.c net: Handle l3mdev in ip_tunnel_init_flow 2024-10-17 15:12:01 +02:00
ip_input.c ipv4: ignore dst hint for multipath routes 2023-09-19 12:22:58 +02:00
ip_options.c net: clean up codestyle for net/ipv4 2020-08-25 06:28:02 -07:00
ip_output.c net: ipv4: fix a memleak in ip_setup_cork 2024-02-23 08:54:54 +01:00
ip_sockglue.c bpf: net: Change do_ip_getsockopt() to take the sockptr_t argument 2024-03-26 18:21:23 -04:00
ip_tunnel.c net/ip6_tunnel: Prevent perpetual tunnel growth 2025-10-29 14:03:08 +01:00
ip_tunnel_core.c tunnels: reset the GSO metadata before reusing the skb 2025-10-02 13:39:02 +02:00
ip_vti.c ip_vti: fix potential slab-use-after-free in decode_session6 2023-08-26 14:23:32 +02:00
ipcomp.c Networking changes for 5.14. 2021-06-30 15:51:09 -07:00
ipconfig.c net: ipconfig: Don't override command-line hostnames or domains 2021-06-02 13:27:03 -07:00
ipip.c ip_tunnel: use ndo_siocdevprivate 2021-07-27 20:11:44 +01:00
ipmr.c ipmr: fix incorrect parameter validation in the ip_mroute_getsockopt() function 2024-03-26 18:21:23 -04:00
ipmr_base.c ipmr: do not call mr_mfc_uses_dev() for unres entries 2025-03-13 12:50:11 +01:00
Kconfig tcp: configurable source port perturb table size 2022-12-02 17:41:11 +01:00
Makefile bpf: Clean up sockmap related Kconfigs 2021-02-26 12:28:03 -08:00
metrics.c ipv4: prevent potential spectre v1 gadget in ip_metrics_convert() 2023-02-01 08:27:27 +01:00
netfilter.c netfilter: Dissect flow after packet mangling 2021-04-18 22:04:16 +02:00
netlink.c treewide: Add SPDX license identifier for missed files 2019-05-21 10:50:45 +02:00
nexthop.c net: When removing nexthops, don't call synchronize_net if it is not necessary 2025-12-07 06:09:19 +09:00
ping.c ping: fix address binding wrt vrf 2022-05-18 10:26:57 +02:00
proc.c minmax: add a few more MIN_T/MAX_T users 2025-10-19 16:21:52 +02:00
protocol.c net: Remove the member netns_ok 2021-05-17 15:29:35 -07:00
raw.c net: drop nopreempt requirement on sock_prot_inuse_add() 2024-07-05 09:14:08 +02:00
raw_diag.c net: Use nlmsg_unicast() instead of netlink_unicast() 2021-07-13 09:28:29 -07:00
route.c ipv4: route: Prevent rt_bind_exception() from rebinding stale fnhe 2025-12-07 06:09:29 +09:00
syncookies.c tcp: fix cookie_init_timestamp() overflows 2023-11-20 11:08:16 +01:00
sysctl_net_ipv4.c tcp: restrict net.ipv4.tcp_app_win 2023-04-20 12:13:53 +02:00
tcp.c tcp: fix __tcp_close() to only send RST when required 2025-10-19 16:21:33 +02:00
tcp_bbr.c tcp: add accessors to read/set tp->snd_cwnd 2022-06-14 18:36:11 +02:00
tcp_bic.c tcp: add accessors to read/set tp->snd_cwnd 2022-06-14 18:36:11 +02:00
tcp_bpf.c tcp_bpf: Call sk_msg_free() when tcp_bpf_send_verdict() fails to allocate psock->cork. 2025-10-02 13:39:00 +02:00
tcp_cdg.c tcp: cdg: allow tcp_cdg_release() to be called multiple times 2022-11-26 09:24:50 +01:00
tcp_cong.c tcp: add accessors to read/set tp->snd_cwnd 2022-06-14 18:36:11 +02:00
tcp_cubic.c tcp_cubic: fix incorrect HyStart round start detection 2025-03-13 12:49:59 +01:00
tcp_dctcp.c tcp: Fix shift-out-of-bounds in dctcp_update_alpha(). 2024-06-16 13:39:47 +02:00
tcp_dctcp.h tcp: refactor DCTCP ECN ACK handling 2018-10-10 22:26:00 -07:00
tcp_diag.c inet_diag: Move the INET_DIAG_REQ_BYTECODE nlattr to cb->data 2020-02-27 18:50:19 -08:00
tcp_fastopen.c tcp: annotate data-races around fastopenq.max_qlen 2023-07-27 08:47:04 +02:00
tcp_highspeed.c tcp: add accessors to read/set tp->snd_cwnd 2022-06-14 18:36:11 +02:00
tcp_htcp.c tcp: add accessors to read/set tp->snd_cwnd 2022-06-14 18:36:11 +02:00
tcp_hybla.c tcp: add accessors to read/set tp->snd_cwnd 2022-06-14 18:36:11 +02:00
tcp_illinois.c tcp: add accessors to read/set tp->snd_cwnd 2022-06-14 18:36:11 +02:00
tcp_input.c tcp: Don't call reqsk_fastopen_remove() in tcp_conn_request(). 2025-10-19 16:21:41 +02:00
tcp_ipv4.c tcp: avoid reusing FIN_WAIT2 when trying to find port in connect() process 2024-10-17 15:11:26 +02:00
tcp_lp.c tcp: add accessors to read/set tp->snd_cwnd 2022-06-14 18:36:11 +02:00
tcp_metrics.c tcp_metrics: validate source addr length 2024-07-18 13:07:30 +02:00
tcp_minisocks.c tcp: Defer ts_recent changes until req is owned 2025-03-13 12:50:57 +01:00
tcp_nv.c tcp: add accessors to read/set tp->snd_cwnd 2022-06-14 18:36:11 +02:00
tcp_offload.c net-timestamp: support TCP GSO case for a few missing flags 2025-03-13 12:51:07 +01:00
tcp_output.c tcp: fix tcp_tso_should_defer() vs large RTT 2025-10-29 14:03:08 +01:00
tcp_rate.c tcp: add accessors to read/set tp->snd_cwnd 2022-06-14 18:36:11 +02:00
tcp_recovery.c tcp: fix excessive TLP and RACK timeouts from HZ rounding 2023-10-25 11:58:57 +02:00
tcp_scalable.c tcp: add accessors to read/set tp->snd_cwnd 2022-06-14 18:36:11 +02:00
tcp_timer.c tcp: fix race in tcp_write_err() 2024-08-19 05:44:56 +02:00
tcp_ulp.c net/ulp: use consistent error code when blocking ULP 2023-01-24 07:22:48 +01:00
tcp_vegas.c tcp: add accessors to read/set tp->snd_cwnd 2022-06-14 18:36:11 +02:00
tcp_vegas.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
tcp_veno.c tcp: add accessors to read/set tp->snd_cwnd 2022-06-14 18:36:11 +02:00
tcp_westwood.c tcp: add accessors to read/set tp->snd_cwnd 2022-06-14 18:36:11 +02:00
tcp_yeah.c tcp: add accessors to read/set tp->snd_cwnd 2022-06-14 18:36:11 +02:00
tunnel4.c net: Remove the member netns_ok 2021-05-17 15:29:35 -07:00
udp.c udp: Fix memory accounting leak. 2025-10-19 16:21:27 +02:00
udp_bpf.c bpf, sockmap: Fix an infinite loop error when len is 0 in tcp_bpf_recvmsg_parser() 2023-03-17 08:48:54 +01:00
udp_diag.c net: Use nlmsg_unicast() instead of netlink_unicast() 2021-07-13 09:28:29 -07:00
udp_impl.h net: pass a sockptr_t into ->setsockopt 2020-07-24 15:41:54 -07:00
udp_offload.c udp: also consider secpath when evaluating ipsec use for checksumming 2025-08-28 16:24:16 +02:00
udp_tunnel_core.c net/tunnel: wait until all sk_user_data reader finish before releasing the sock 2022-12-31 13:14:19 +01:00
udp_tunnel_nic.c udp_tunnel: use netdev_warn() instead of netdev_WARN() 2025-12-07 06:09:22 +09:00
udp_tunnel_stub.c udp_tunnel: add central NIC RX port offload infrastructure 2020-07-10 13:54:00 -07:00
udplite.c udplite: Fix NULL pointer dereference in __sk_mem_raise_allocated(). 2023-05-30 13:55:31 +01:00
xfrm4_input.c xfrm: Preserve vlan tags for transport mode software GRO 2024-05-17 11:50:57 +02:00
xfrm4_output.c xfrm: fix unused variable warning if CONFIG_NETFILTER=n 2020-05-11 15:12:27 +02:00
xfrm4_policy.c xfrm: respect ip protocols rules criteria when performing dst lookups 2024-11-01 01:52:36 +01:00
xfrm4_protocol.c net: xfrm: unexport __init-annotated xfrm4_protocol_init() 2022-06-14 18:36:18 +02:00
xfrm4_state.c xfrm: remove output_finish indirection from xfrm_state_afinfo 2020-05-06 09:40:08 +02:00
xfrm4_tunnel.c xfrm: remove description from xfrm_type struct 2021-06-09 09:38:52 +02:00