kernel/linux.git/net/ipv4/syncookies.c, branch v6.18.21

tcp: secure_seq: add back ports to TS offset

2026-03-12T11:09:58+00:00

[ Upstream commit 165573e41f2f66ef98940cf65f838b2cb575d9d1 ] This reverts 28ee1b746f49 ("secure_seq: downgrade to per-host timestamp offsets") tcp_tw_recycle went away in 2017. Zhouyan Deng reported off-path TCP source port leakage via SYN cookie side-channel that can be fixed in multiple ways. One of them is to bring back TCP ports in TS offset randomization. As a bonus, we perform a single siphash() computation to provide both an ISN and a TS offset. Fixes: 28ee1b746f49 ("secure_seq: downgrade to per-host timestamp offsets") Reported-by: Zhouyan Deng Signed-off-by: Eric Dumazet Reviewed-by: Kuniyuki Iwashima Acked-by: Florian Westphal Link: https://patch.msgid.link/20260302205527.1982836-1-edumazet@google.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin

tcp: fix potential race in tcp_v6_syn_recv_sock()

2026-03-04T12:20:44+00:00

[ Upstream commit 858d2a4f67ff69e645a43487ef7ea7f28f06deae ] Code in tcp_v6_syn_recv_sock() after the call to tcp_v4_syn_recv_sock() is done too late. After tcp_v4_syn_recv_sock(), the child socket is already visible from TCP ehash table and other cpus might use it. Since newinet->pinet6 is still pointing to the listener ipv6_pinfo bad things can happen as syzbot found. Move the problematic code in tcp_v6_mapped_child_init() and call this new helper from tcp_v4_syn_recv_sock() before the ehash insertion. This allows the removal of one tcp_sync_mss(), since tcp_v4_syn_recv_sock() will call it with the correct context. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Reported-by: syzbot+937b5bbb6a815b3e5d0b@syzkaller.appspotmail.com Closes: https://lore.kernel.org/netdev/69949275.050a0220.2eeac1.0145.GAE@google.com/ Signed-off-by: Eric Dumazet Reviewed-by: Kuniyuki Iwashima Link: https://patch.msgid.link/20260217161205.2079883-1-edumazet@google.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin

tcp: accecn: AccECN negotiation

2025-09-18T06:47:51+00:00

Accurate ECN negotiation parts based on the specification: https://tools.ietf.org/id/draft-ietf-tcpm-accurate-ecn-28.txt Accurate ECN is negotiated using ECE, CWR and AE flags in the TCP header. TCP falls back into using RFC3168 ECN if one of the ends supports only RFC3168-style ECN. The AccECN negotiation includes reflecting IP ECN field value seen in SYN and SYNACK back using the same bits as negotiation to allow responding to SYN CE marks and to detect ECN field mangling. CE marks should not occur currently because SYN=1 segments are sent with Non-ECT in IP ECN field (but proposal exists to remove this restriction). Reflecting SYN IP ECN field in SYNACK is relatively simple. Reflecting SYNACK IP ECN field in the final/third ACK of the handshake is more challenging. Linux TCP code is not well prepared for using the final/third ACK a signalling channel which makes things somewhat complicated here. tcp_ecn sysctl can be used to select the highest ECN variant (Accurate ECN, ECN, No ECN) that is attemped to be negotiated and requested for incoming connection and outgoing connection: TCP_ECN_IN_NOECN_OUT_NOECN, TCP_ECN_IN_ECN_OUT_ECN, TCP_ECN_IN_ECN_OUT_NOECN, TCP_ECN_IN_ACCECN_OUT_ACCECN, TCP_ECN_IN_ACCECN_OUT_ECN, and TCP_ECN_IN_ACCECN_OUT_NOECN. After this patch, the size of tcp_request_sock remains unchanged and no new holes are added. Below are the pahole outcomes before and after this patch: [BEFORE THIS PATCH] struct tcp_request_sock { [...] u32 rcv_nxt; /* 352 4 */ u8 syn_tos; /* 356 1 */ /* size: 360, cachelines: 6, members: 16 */ } [AFTER THIS PATCH] struct tcp_request_sock { [...] u32 rcv_nxt; /* 352 4 */ u8 syn_tos; /* 356 1 */ bool accecn_ok; /* 357 1 */ u8 syn_ect_snt:2; /* 358: 0 1 */ u8 syn_ect_rcv:2; /* 358: 2 1 */ u8 accecn_fail_mode:4; /* 358: 4 1 */ /* size: 360, cachelines: 6, members: 20 */ } After this patch, the size of tcp_sock remains unchanged and no new holes are added. Also, 4 bits of the existing 2-byte hole are exploited. Below are the pahole outcomes before and after this patch: [BEFORE THIS PATCH] struct tcp_sock { [...] u8 dup_ack_counter:2; /* 2761: 0 1 */ u8 tlp_retrans:1; /* 2761: 2 1 */ u8 unused:5; /* 2761: 3 1 */ u8 thin_lto:1; /* 2762: 0 1 */ u8 fastopen_connect:1; /* 2762: 1 1 */ u8 fastopen_no_cookie:1; /* 2762: 2 1 */ u8 fastopen_client_fail:2; /* 2762: 3 1 */ u8 frto:1; /* 2762: 5 1 */ /* XXX 2 bits hole, try to pack */ [...] u8 keepalive_probes; /* 2765 1 */ /* XXX 2 bytes hole, try to pack */ [...] /* size: 3200, cachelines: 50, members: 164 */ } [AFTER THIS PATCH] struct tcp_sock { [...] u8 dup_ack_counter:2; /* 2761: 0 1 */ u8 tlp_retrans:1; /* 2761: 2 1 */ u8 syn_ect_snt:2; /* 2761: 3 1 */ u8 syn_ect_rcv:2; /* 2761: 5 1 */ u8 thin_lto:1; /* 2761: 7 1 */ u8 fastopen_connect:1; /* 2762: 0 1 */ u8 fastopen_no_cookie:1; /* 2762: 1 1 */ u8 fastopen_client_fail:2; /* 2762: 2 1 */ u8 frto:1; /* 2762: 4 1 */ /* XXX 3 bits hole, try to pack */ [...] u8 keepalive_probes; /* 2765 1 */ u8 accecn_fail_mode:4; /* 2766: 0 1 */ /* XXX 4 bits hole, try to pack */ /* XXX 1 byte hole, try to pack */ [...] /* size: 3200, cachelines: 50, members: 166 */ } Signed-off-by: Ilpo Järvinen Co-developed-by: Olivier Tilmans Signed-off-by: Olivier Tilmans Co-developed-by: Chia-Yu Chang Signed-off-by: Chia-Yu Chang Acked-by: Paolo Abeni Reviewed-by: Eric Dumazet Link: https://patch.msgid.link/20250916082434.100722-3-chia-yu.chang@nokia-bell-labs.com Signed-off-by: Paolo Abeni

net: annotate races around sk->sk_uid

2025-06-24T00:04:03+00:00

sk->sk_uid can be read while another thread changes its value in sockfs_setattr(). Add sk_uid(const struct sock *sk) helper to factorize the needed READ_ONCE() annotations, and add corresponding WRITE_ONCE() where needed. Fixes: 86741ec25462 ("net: core: Add a UID field to struct sock.") Signed-off-by: Eric Dumazet Cc: Lorenzo Colitti Reviewed-by: Maciej Żenczykowski Link: https://patch.msgid.link/20250620133001.4090592-2-edumazet@google.com Signed-off-by: Jakub Kicinski

tcp: be less liberal in TSEcr received while in SYN_RECV state

2025-02-27T02:11:17+00:00

Yong-Hao Zou mentioned that linux was not strict as other OS in 3WHS, for flows using TCP TS option (RFC 7323) As hinted by an old comment in tcp_check_req(), we can check the TSEcr value in the incoming packet corresponds to one of the SYNACK TSval values we have sent. In this patch, I record the oldest and most recent values that SYNACK packets have used. Send a challenge ACK if we receive a TSEcr outside of this range, and increase a new SNMP counter. nstat -az | grep TSEcrRejected TcpExtTSEcrRejected 0 0.0 Due to TCP fastopen implementation, do not apply yet these checks for fastopen flows. v2: No longer use req->num_timeout, but treq->snt_tsval_first to detect when first SYNACK is prepared. This means we make sure to not send an initial zero TSval. Make sure MPTCP and TCP selftests are passing. Change MIB name to TcpExtTSEcrRejected v1: https://lore.kernel.org/netdev/CADVnQykD8i4ArpSZaPKaoNxLJ2if2ts9m4As+=Jvdkrgx1qMHw@mail.gmail.com/T/ Reported-by: Yong-Hao Zou Signed-off-by: Eric Dumazet Reviewed-by: Matthieu Baerts (NGI0) Reviewed-by: Neal Cardwell Reviewed-by: Kuniyuki Iwashima Link: https://patch.msgid.link/20250225171048.3105061-1-edumazet@google.com Signed-off-by: Jakub Kicinski

tcp: use EXPORT_IPV6_MOD[_GPL]()

2025-02-14T21:09:39+00:00

Use EXPORT_IPV6_MOD[_GPL]() for symbols that don't need to be exported unless CONFIG_IPV6=m tcp_hashinfo and tcp_openreq_init_rwin() are no longer used from any module anyway. Signed-off-by: Eric Dumazet Reviewed-by: Kuniyuki Iwashima Reviewed-by: Mateusz Polchlopek Link: https://patch.msgid.link/20250212132418.1524422-4-edumazet@google.com Signed-off-by: Jakub Kicinski

tcp: use sk_skb_reason_drop to free rx packets

2024-06-19T11:44:22+00:00

Replace kfree_skb_reason with sk_skb_reason_drop and pass the receiving socket to the tracepoint. Reported-by: kernel test robot Closes: https://lore.kernel.org/r/202406011539.jhwBd7DX-lkp@intel.com/ Signed-off-by: Yan Zhai Acked-by: Jesper Dangaard Brouer Signed-off-by: David S. Miller

tcp: annotate data-races around tp->window_clamp

2024-04-06T05:32:37+00:00

tp->window_clamp can be read locklessly, add READ_ONCE() and WRITE_ONCE() annotations. Signed-off-by: Eric Dumazet Reviewed-by: Jason Xing Link: https://lore.kernel.org/r/20240404114231.2195171-1-edumazet@google.com Signed-off-by: Jakub Kicinski

tcp: Clear req->syncookie in reqsk_alloc().

2024-03-20T02:35:59+00:00

syzkaller reported a read of uninit req->syncookie. [0] Originally, req->syncookie was used only in tcp_conn_request() to indicate if we need to encode SYN cookie in SYN+ACK, so the field remains uninitialised in other places. The commit 695751e31a63 ("bpf: tcp: Handle BPF SYN Cookie in cookie_v[46]_check().") added another meaning in ACK path; req->syncookie is set true if SYN cookie is validated by BPF kfunc. After the change, cookie_v[46]_check() always read req->syncookie, but it is not initialised in the normal SYN cookie case as reported by KMSAN. Let's make sure we always initialise req->syncookie in reqsk_alloc(). [0]: BUG: KMSAN: uninit-value in cookie_v4_check+0x22b7/0x29e0 net/ipv4/syncookies.c:477 cookie_v4_check+0x22b7/0x29e0 net/ipv4/syncookies.c:477 tcp_v4_cookie_check net/ipv4/tcp_ipv4.c:1855 [inline] tcp_v4_do_rcv+0xb17/0x10b0 net/ipv4/tcp_ipv4.c:1914 tcp_v4_rcv+0x4ce4/0x5420 net/ipv4/tcp_ipv4.c:2322 ip_protocol_deliver_rcu+0x2a3/0x13d0 net/ipv4/ip_input.c:205 ip_local_deliver_finish+0x332/0x500 net/ipv4/ip_input.c:233 NF_HOOK include/linux/netfilter.h:314 [inline] ip_local_deliver+0x21f/0x490 net/ipv4/ip_input.c:254 dst_input include/net/dst.h:460 [inline] ip_rcv_finish+0x4a2/0x520 net/ipv4/ip_input.c:449 NF_HOOK include/linux/netfilter.h:314 [inline] ip_rcv+0xcd/0x380 net/ipv4/ip_input.c:569 __netif_receive_skb_one_core net/core/dev.c:5538 [inline] __netif_receive_skb+0x319/0x9e0 net/core/dev.c:5652 process_backlog+0x480/0x8b0 net/core/dev.c:5981 __napi_poll+0xe7/0x980 net/core/dev.c:6632 napi_poll net/core/dev.c:6701 [inline] net_rx_action+0x89d/0x1820 net/core/dev.c:6813 __do_softirq+0x1c0/0x7d7 kernel/softirq.c:554 do_softirq+0x9a/0x100 kernel/softirq.c:455 __local_bh_enable_ip+0x9f/0xb0 kernel/softirq.c:382 local_bh_enable include/linux/bottom_half.h:33 [inline] rcu_read_unlock_bh include/linux/rcupdate.h:820 [inline] __dev_queue_xmit+0x2776/0x52c0 net/core/dev.c:4362 dev_queue_xmit include/linux/netdevice.h:3091 [inline] neigh_hh_output include/net/neighbour.h:526 [inline] neigh_output include/net/neighbour.h:540 [inline] ip_finish_output2+0x187a/0x1b70 net/ipv4/ip_output.c:235 __ip_finish_output+0x287/0x810 ip_finish_output+0x4b/0x550 net/ipv4/ip_output.c:323 NF_HOOK_COND include/linux/netfilter.h:303 [inline] ip_output+0x15f/0x3f0 net/ipv4/ip_output.c:433 dst_output include/net/dst.h:450 [inline] ip_local_out net/ipv4/ip_output.c:129 [inline] __ip_queue_xmit+0x1e93/0x2030 net/ipv4/ip_output.c:535 ip_queue_xmit+0x60/0x80 net/ipv4/ip_output.c:549 __tcp_transmit_skb+0x3c70/0x4890 net/ipv4/tcp_output.c:1462 tcp_transmit_skb net/ipv4/tcp_output.c:1480 [inline] tcp_write_xmit+0x3ee1/0x8900 net/ipv4/tcp_output.c:2792 __tcp_push_pending_frames net/ipv4/tcp_output.c:2977 [inline] tcp_send_fin+0xa90/0x12e0 net/ipv4/tcp_output.c:3578 tcp_shutdown+0x198/0x1f0 net/ipv4/tcp.c:2716 inet_shutdown+0x33f/0x5b0 net/ipv4/af_inet.c:923 __sys_shutdown_sock net/socket.c:2425 [inline] __sys_shutdown net/socket.c:2437 [inline] __do_sys_shutdown net/socket.c:2445 [inline] __se_sys_shutdown+0x2a4/0x440 net/socket.c:2443 __x64_sys_shutdown+0x6c/0xa0 net/socket.c:2443 do_syscall_64+0xd5/0x1f0 entry_SYSCALL_64_after_hwframe+0x6d/0x75 Uninit was stored to memory at: reqsk_alloc include/net/request_sock.h:148 [inline] inet_reqsk_alloc+0x651/0x7a0 net/ipv4/tcp_input.c:6978 cookie_tcp_reqsk_alloc+0xd4/0x900 net/ipv4/syncookies.c:328 cookie_tcp_check net/ipv4/syncookies.c:388 [inline] cookie_v4_check+0x289f/0x29e0 net/ipv4/syncookies.c:420 tcp_v4_cookie_check net/ipv4/tcp_ipv4.c:1855 [inline] tcp_v4_do_rcv+0xb17/0x10b0 net/ipv4/tcp_ipv4.c:1914 tcp_v4_rcv+0x4ce4/0x5420 net/ipv4/tcp_ipv4.c:2322 ip_protocol_deliver_rcu+0x2a3/0x13d0 net/ipv4/ip_input.c:205 ip_local_deliver_finish+0x332/0x500 net/ipv4/ip_input.c:233 NF_HOOK include/linux/netfilter.h:314 [inline] ip_local_deliver+0x21f/0x490 net/ipv4/ip_input.c:254 dst_input include/net/dst.h:460 [inline] ip_rcv_finish+0x4a2/0x520 net/ipv4/ip_input.c:449 NF_HOOK include/linux/netfilter.h:314 [inline] ip_rcv+0xcd/0x380 net/ipv4/ip_input.c:569 __netif_receive_skb_one_core net/core/dev.c:5538 [inline] __netif_receive_skb+0x319/0x9e0 net/core/dev.c:5652 process_backlog+0x480/0x8b0 net/core/dev.c:5981 __napi_poll+0xe7/0x980 net/core/dev.c:6632 napi_poll net/core/dev.c:6701 [inline] net_rx_action+0x89d/0x1820 net/core/dev.c:6813 __do_softirq+0x1c0/0x7d7 kernel/softirq.c:554 Uninit was created at: __alloc_pages+0x9a7/0xe00 mm/page_alloc.c:4592 __alloc_pages_node include/linux/gfp.h:238 [inline] alloc_pages_node include/linux/gfp.h:261 [inline] alloc_slab_page mm/slub.c:2175 [inline] allocate_slab mm/slub.c:2338 [inline] new_slab+0x2de/0x1400 mm/slub.c:2391 ___slab_alloc+0x1184/0x33d0 mm/slub.c:3525 __slab_alloc mm/slub.c:3610 [inline] __slab_alloc_node mm/slub.c:3663 [inline] slab_alloc_node mm/slub.c:3835 [inline] kmem_cache_alloc+0x6d3/0xbe0 mm/slub.c:3852 reqsk_alloc include/net/request_sock.h:131 [inline] inet_reqsk_alloc+0x66/0x7a0 net/ipv4/tcp_input.c:6978 tcp_conn_request+0x484/0x44e0 net/ipv4/tcp_input.c:7135 tcp_v4_conn_request+0x16f/0x1d0 net/ipv4/tcp_ipv4.c:1716 tcp_rcv_state_process+0x2e5/0x4bb0 net/ipv4/tcp_input.c:6655 tcp_v4_do_rcv+0xbfd/0x10b0 net/ipv4/tcp_ipv4.c:1929 tcp_v4_rcv+0x4ce4/0x5420 net/ipv4/tcp_ipv4.c:2322 ip_protocol_deliver_rcu+0x2a3/0x13d0 net/ipv4/ip_input.c:205 ip_local_deliver_finish+0x332/0x500 net/ipv4/ip_input.c:233 NF_HOOK include/linux/netfilter.h:314 [inline] ip_local_deliver+0x21f/0x490 net/ipv4/ip_input.c:254 dst_input include/net/dst.h:460 [inline] ip_sublist_rcv_finish net/ipv4/ip_input.c:580 [inline] ip_list_rcv_finish net/ipv4/ip_input.c:631 [inline] ip_sublist_rcv+0x15f3/0x17f0 net/ipv4/ip_input.c:639 ip_list_rcv+0x9ef/0xa40 net/ipv4/ip_input.c:674 __netif_receive_skb_list_ptype net/core/dev.c:5581 [inline] __netif_receive_skb_list_core+0x15c5/0x1670 net/core/dev.c:5629 __netif_receive_skb_list net/core/dev.c:5681 [inline] netif_receive_skb_list_internal+0x106c/0x16f0 net/core/dev.c:5773 gro_normal_list include/net/gro.h:438 [inline] napi_complete_done+0x425/0x880 net/core/dev.c:6113 virtqueue_napi_complete drivers/net/virtio_net.c:465 [inline] virtnet_poll+0x149d/0x2240 drivers/net/virtio_net.c:2211 __napi_poll+0xe7/0x980 net/core/dev.c:6632 napi_poll net/core/dev.c:6701 [inline] net_rx_action+0x89d/0x1820 net/core/dev.c:6813 __do_softirq+0x1c0/0x7d7 kernel/softirq.c:554 CPU: 0 PID: 16792 Comm: syz-executor.2 Not tainted 6.8.0-syzkaller-05562-g61387b8dcf1d #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/29/2024 Fixes: 695751e31a63 ("bpf: tcp: Handle BPF SYN Cookie in cookie_v[46]_check().") Reported-by: syzkaller Reported-by: Eric Dumazet Closes: https://lore.kernel.org/bpf/CANn89iKdN9c+C_2JAUbc+VY3DDQjAQukMtiBbormAmAk9CdvQA@mail.gmail.com/ Signed-off-by: Kuniyuki Iwashima Reviewed-by: Eric Dumazet Acked-by: Martin KaFai Lau Link: https://lore.kernel.org/r/20240315224710.55209-1-kuniyu@amazon.com Signed-off-by: Jakub Kicinski

tcp: use drop reasons in cookie check for ipv4

2024-02-28T10:39:21+00:00

Now it's time to use the prepared definitions to refine this part. Four reasons used might enough for now, I think. Signed-off-by: Jason Xing Reviewed-by: Eric Dumazet Reviewed-by: David Ahern Reviewed-by: Kuniyuki Iwashima Signed-off-by: David S. Miller