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d887a33724
linux/net/ipv4
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Eric Dumazet d887a33724 ipv4: tcp: send zero IPID in SYNACK messages 
[ Upstream commit 970a5a3ea8 ]

In commit 431280eebe ("ipv4: tcp: send zero IPID for RST and
ACK sent in SYN-RECV and TIME-WAIT state") we took care of some
ctl packets sent by TCP.

It turns out we need to use a similar strategy for SYNACK packets.

By default, they carry IP_DF and IPID==0, but there are ways
to ask them to use the hashed IP ident generator and thus
be used to build off-path attacks.
(Ref: Off-Path TCP Exploits of the Mixed IPID Assignment)

One of this way is to force (before listener is started)
echo 1 >/proc/sys/net/ipv4/ip_no_pmtu_disc

Another way is using forged ICMP ICMP_FRAG_NEEDED
with a very small MTU (like 68) to force a false return from
ip_dont_fragment()

In this patch, ip_build_and_send_pkt() uses the following
heuristics.

1) Most SYNACK packets are smaller than IPV4_MIN_MTU and therefore
can use IP_DF regardless of the listener or route pmtu setting.

2) In case the SYNACK packet is bigger than IPV4_MIN_MTU,
we use prandom_u32() generator instead of the IPv4 hashed ident one.

Fixes: 1da177e4c3 ("Linux-2.6.12-rc2")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Ray Che <xijiache@gmail.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Cc: Geoff Alexander <alexandg@cs.unm.edu>
Cc: Willy Tarreau <w@1wt.eu>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
2022-02-01 17:27:14 +01:00
..
bpfilter
netfilter netfilter: ipt_CLUSTERIP: fix refcount leak in clusterip_tg_check() 2022-01-27 11:03:50 +01:00
af_inet.c net: fix use-after-free in tw_timer_handler 2022-01-05 12:42:39 +01:00
ah4.c Networking changes for 5.14. 2021-06-30 15:51:09 -07:00
arp.c net: Exempt multicast addresses from five-second neighbor lifetime 2020-11-13 14:24:39 -08:00
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 net: remove the unnecessary check in cipso_v4_doi_free 2021-09-03 13:52:29 +01:00
datagram.c
devinet.c net: return correct error code 2021-12-08 09:04:38 +01:00
esp4_offload.c xfrm: remove description from xfrm_type struct 2021-06-09 09:38:52 +02:00
esp4.c ipsec: Remove unneeded extra variable in esp4 esp_ssg_unref() 2021-07-20 16:14:23 +02:00
fib_frontend.c ipv4: convert fib_num_tclassid_users to atomic_t 2021-12-08 09:04:49 +01:00
fib_lookup.h ipv4: Fix spelling mistakes 2021-06-07 14:08:30 -07:00
fib_notifier.c
fib_rules.c ipv4: convert fib_num_tclassid_users to atomic_t 2021-12-08 09:04:49 +01:00
fib_semantics.c ipv4: avoid quadratic behavior in netns dismantle 2022-01-27 11:05:27 +01:00
fib_trie.c memcg: enable accounting for IP address and routing-related objects 2021-07-20 06:00:38 -07:00
fou.c fou: remove sparse errors 2021-08-31 12:03:33 +01:00
gre_demux.c net: Remove the member netns_ok 2021-05-17 15:29:35 -07:00
gre_offload.c ip_gre: add csum offload support for gre header 2021-01-29 20:39:14 -08:00
icmp.c icmp: fix icmp_ext_echo_iio parsing in icmp_build_probe 2021-10-14 07:54:47 -07:00
igmp.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2021-08-13 06:41:22 -07:00
inet_connection_sock.c inet: use #ifdef CONFIG_SOCK_RX_QUEUE_MAPPING consistently 2021-12-17 10:30:13 +01:00
inet_diag.c inet_diag: fix kernel-infoleak for UDP sockets 2021-12-22 09:32:40 +01:00
inet_fragment.c inet: frags: annotate races around fqdir->dead and fqdir->high_thresh 2022-01-27 11:05:35 +01:00
inet_hashtables.c tcp: switch orphan_count to bare per-cpu counters 2021-11-18 19:16:33 +01:00
inet_timewait_sock.c
inetpeer.c inetpeer: use div64_ul() and clamp_val() calculate inet_peer_threshold 2021-03-01 13:32:12 -08:00
ip_forward.c
ip_fragment.c inet: frags: annotate races around fqdir->dead and fqdir->high_thresh 2022-01-27 11:05:35 +01:00
ip_gre.c gre: Don't accidentally set RTO_ONLINK in gre_fill_metadata_dst() 2022-01-27 11:05:36 +01:00
ip_input.c net: use indirect call helpers for dst_input 2021-02-03 14:51:39 -08:00
ip_options.c
ip_output.c ipv4: tcp: send zero IPID in SYNACK messages 2022-02-01 17:27:14 +01:00
ip_sockglue.c Revert "Revert "ipv4: fix memory leaks in ip_cmsg_send() callers"" 2021-09-14 14:24:31 +01:00
ip_tunnel_core.c net: ip_tunnel: clean up endianness conversions 2021-01-08 19:25:35 -08:00
ip_tunnel.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2021-07-31 09:14:46 -07:00
ip_vti.c ip_tunnel: use ndo_siocdevprivate 2021-07-27 20:11:44 +01:00
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_base.c
ipmr.c ipmr: Fix indentation issue 2021-07-07 20:52:25 -07:00
Kconfig
Makefile bpf: Clean up sockmap related Kconfigs 2021-02-26 12:28:03 -08:00
metrics.c treewide: rename nla_strlcpy to nla_strscpy. 2020-11-16 08:08:54 -08:00
netfilter.c netfilter: Dissect flow after packet mangling 2021-04-18 22:04:16 +02:00
netlink.c
nexthop.c net: nexthop: release IPv6 per-cpu dsts when replacing a nexthop group 2021-12-01 09:04:49 +01:00
ping.c ping: fix the sk_bound_dev_if match in ping_lookup 2022-02-01 17:27:08 +01:00
proc.c tcp: switch orphan_count to bare per-cpu counters 2021-11-18 19:16:33 +01:00
protocol.c net: Remove the member netns_ok 2021-05-17 15:29:35 -07:00
raw_diag.c net: Use nlmsg_unicast() instead of netlink_unicast() 2021-07-13 09:28:29 -07:00
raw.c ipv4: raw: lock the socket in raw_bind() 2022-02-01 17:27:14 +01:00
route.c ipv4: fix endianness issue in inet_rtm_getroute_build_skb() 2021-08-31 12:03:03 +01:00
syncookies.c selinux/stable-5.11 PR 20201214 2020-12-16 11:01:04 -08:00
sysctl_net_ipv4.c net: Introduce net.ipv4.tcp_migrate_req. 2021-06-15 18:01:05 +02:00
tcp_bbr.c tcp_bbr: fix u32 wrap bug in round logic if bbr_init() called after 2B packets 2021-08-11 15:00:15 -07:00
tcp_bic.c
tcp_bpf.c bpf, sockmap: Fix return codes from tcp_bpf_recvmsg_parser() 2022-01-27 11:03:50 +01:00
tcp_cdg.c
tcp_cong.c net: Only allow init netns to set default tcp cong to a restricted algo 2021-05-04 11:58:28 -07:00
tcp_cubic.c tcp_cubic: fix spurious Hystart ACK train detections for not-cwnd-limited flows 2021-12-01 09:04:52 +01:00
tcp_dctcp.c
tcp_dctcp.h
tcp_diag.c
tcp_fastopen.c tcp: enable data-less, empty-cookie SYN with TFO_SERVER_COOKIE_NOT_REQD 2021-08-16 17:25:49 -07:00
tcp_highspeed.c
tcp_htcp.c
tcp_hybla.c
tcp_illinois.c
tcp_input.c inet: fully convert sk->sk_rx_dst to RCU rules 2021-12-29 12:28:42 +01:00
tcp_ipv4.c inet: fully convert sk->sk_rx_dst to RCU rules 2021-12-29 12:28:42 +01:00
tcp_lp.c ipv4: tcp_lp.c: Couple of typo fixes 2021-03-28 17:31:13 -07:00
tcp_metrics.c fixes-v5.11 2020-12-14 16:40:27 -08:00
tcp_minisocks.c tcp: Add stats for socket migration. 2021-06-23 12:56:08 -07:00
tcp_nv.c
tcp_offload.c net, gro: Set inner transport header offset in tcp/udp GRO hook 2021-08-02 10:20:56 +01:00
tcp_output.c net: add and use skb_unclone_keeptruesize() helper 2021-11-25 09:49:08 +01:00
tcp_rate.c
tcp_recovery.c tcp: more accurately check DSACKs to grow RACK reordering window 2021-07-27 20:07:21 +01:00
tcp_scalable.c
tcp_timer.c net: sock: introduce sk_error_report 2021-06-29 11:28:21 -07:00
tcp_ulp.c
tcp_vegas.c tcp: use semicolons rather than commas to separate statements 2020-10-13 17:11:52 -07:00
tcp_vegas.h
tcp_veno.c
tcp_westwood.c
tcp_yeah.c tcp_yeah: check struct yeah size at compile time 2021-06-29 11:54:36 -07:00
tcp.c inet: fully convert sk->sk_rx_dst to RCU rules 2021-12-29 12:28:42 +01:00
tunnel4.c net: Remove the member netns_ok 2021-05-17 15:29:35 -07:00
udp_bpf.c net: Implement ->sock_is_readable() for UDP and AF_UNIX 2021-10-26 12:29:33 -07:00
udp_diag.c net: Use nlmsg_unicast() instead of netlink_unicast() 2021-07-13 09:28:29 -07:00
udp_impl.h
udp_offload.c fou: remove sparse errors 2021-08-31 12:03:33 +01:00
udp_tunnel_core.c udp_tunnel: reshuffle NETIF_F_RX_UDP_TUNNEL_PORT checks 2021-01-07 12:53:29 -08:00
udp_tunnel_nic.c udp_tunnel: Fix udp_tunnel_nic work-queue type 2021-09-13 12:38:45 +01:00
udp_tunnel_stub.c
udp.c net: udp: fix alignment problem in udp4_seq_show() 2022-01-11 15:35:18 +01:00
udplite.c net: Remove the member netns_ok 2021-05-17 15:29:35 -07:00
xfrm4_input.c
xfrm4_output.c
xfrm4_policy.c
xfrm4_protocol.c net: Remove the member netns_ok 2021-05-17 15:29:35 -07:00
xfrm4_state.c
xfrm4_tunnel.c xfrm: remove description from xfrm_type struct 2021-06-09 09:38:52 +02:00