kernel/linux.git/net/ipv4/tcp.c, branch v7.1

tcp: fix stale per-CPU tcp_tw_isn leak enabling ISN prediction

2026-05-21T02:14:06+00:00

Blamed commit moved the TIME_WAIT-derived ISN from the skb control block to a per-CPU variable, assuming the value would always be consumed by tcp_conn_request() for the same packet that wrote it. That assumption is violated by multiple drop paths between the producer (__this_cpu_write(tcp_tw_isn, isn) in tcp_v{4,6}_rcv()) and the consumer (tcp_conn_request()): - min_ttl / min_hopcount check - xfrm policy check - tcp_inbound_hash() MD5/AO mismatch - tcp_filter() eBPF/SO_ATTACH_FILTER drop - th->syn && th->fin discard in tcp_rcv_state_process() TCP_LISTEN - psp_sk_rx_policy_check() in tcp_v{4,6}_do_rcv() - tcp_checksum_complete() in tcp_v{4,6}_do_rcv() - tcp_v{4,6}_cookie_check() returning NULL When a packet is dropped on any of these paths, tcp_tw_isn is left set. The next SYN processed on the same CPU then consumes the non zero value in tcp_conn_request(), receiving a potentially predictable ISN. This patch moves back tcp_tw_isn to skb->cb[], getting rid of the per-cpu variable. Note that tcp_v{4,6}_fill_cb() do not set it. Very litle impact on overall code size/complexity: $ scripts/bloat-o-meter -t vmlinux.old vmlinux.new add/remove: 0/0 grow/shrink: 2/1 up/down: 8/-15 (-7) Function old new delta tcp_v6_rcv 3038 3042 +4 tcp_v4_rcv 3035 3039 +4 tcp_conn_request 2938 2923 -15 Total: Before=24436060, After=24436053, chg -0.00% Fixes: 41eecbd712b7 ("tcp: replace TCP_SKB_CB(skb)->tcp_tw_isn with a per-cpu field") Reported-by: Chris Mason Signed-off-by: Eric Dumazet Reviewed-by: Kuniyuki Iwashima Link: https://patch.msgid.link/20260519084611.2485277-1-edumazet@google.com Signed-off-by: Jakub Kicinski

Merge tag 'net-7.1-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net

2026-04-23T23:50:42+00:00

Pull networking fixes from Jakub Kicinski: "Including fixes from Netfilter. Steady stream of fixes. Last two weeks feel comparable to the two weeks before the merge window. Lots of AI-aided bug discovery. A newer big source is Sashiko/Gemini (Roman Gushchin's system), which points out issues in existing code during patch review (maybe 25% of fixes here likely originating from Sashiko). Nice thing is these are often fixed by the respective maintainers, not drive-bys. Current release - new code bugs: - kconfig: MDIO_PIC64HPSC should depend on ARCH_MICROCHIP Previous releases - regressions: - add async ndo_set_rx_mode and switch drivers which we promised to be called under the per-netdev mutex to it - dsa: remove duplicate netdev_lock_ops() for conduit ethtool ops - hv_sock: report EOF instead of -EIO for FIN - vsock/virtio: fix MSG_PEEK calculation on bytes to copy Previous releases - always broken: - ipv6: fix possible UAF in icmpv6_rcv() - icmp: validate reply type before using icmp_pointers - af_unix: drop all SCM attributes for SOCKMAP - netfilter: fix a number of bugs in the osf (OS fingerprinting) - eth: intel: fix timestamp interrupt configuration for E825C Misc: - bunch of data-race annotations" * tag 'net-7.1-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net: (148 commits) rxrpc: Fix error handling in rxgk_extract_token() rxrpc: Fix re-decryption of RESPONSE packets rxrpc: Fix rxrpc_input_call_event() to only unshare DATA packets rxrpc: Fix missing validation of ticket length in non-XDR key preparsing rxgk: Fix potential integer overflow in length check rxrpc: Fix conn-level packet handling to unshare RESPONSE packets rxrpc: Fix potential UAF after skb_unshare() failure rxrpc: Fix rxkad crypto unalignment handling rxrpc: Fix memory leaks in rxkad_verify_response() net: rds: fix MR cleanup on copy error m68k: mvme147: Make me the maintainer net: txgbe: fix firmware version check selftests/bpf: check epoll readiness during reuseport migration tcp: call sk_data_ready() after listener migration vhost_net: fix sleeping with preempt-disabled in vhost_net_busy_poll() ipv6: Cap TLV scan in ip6_tnl_parse_tlv_enc_lim tipc: fix double-free in tipc_buf_append() llc: Return -EINPROGRESS from llc_ui_connect() ipv4: icmp: validate reply type before using icmp_pointers selftests/net: packetdrill: cover RFC 5961 5.2 challenge ACK on both edges ...

tcp: annotate data-races around tp->plb_rehash

2026-04-18T18:10:14+00:00

tcp_get_timestamping_opt_stats() intentionally runs lockless, we must add READ_ONCE() and WRITE_ONCE() annotations to keep KCSAN happy. Fixes: 29c1c44646ae ("tcp: add u32 counter in tcp_sock and an SNMP counter for PLB") Signed-off-by: Eric Dumazet Link: https://patch.msgid.link/20260416200319.3608680-15-edumazet@google.com Signed-off-by: Jakub Kicinski

tcp: annotate data-races around (tp->write_seq - tp->snd_nxt)

2026-04-18T18:10:13+00:00

tcp_get_timestamping_opt_stats() intentionally runs lockless, we must add READ_ONCE() annotations to keep KCSAN happy. WRITE_ONCE() annotations are already present. Fixes: e08ab0b377a1 ("tcp: add bytes not sent to SCM_TIMESTAMPING_OPT_STATS") Signed-off-by: Eric Dumazet Link: https://patch.msgid.link/20260416200319.3608680-14-edumazet@google.com Signed-off-by: Jakub Kicinski

tcp: annotate data-races around tp->timeout_rehash

2026-04-18T18:10:13+00:00

tcp_get_timestamping_opt_stats() intentionally runs lockless, we must add READ_ONCE() and WRITE_ONCE() annotations to keep KCSAN happy. Fixes: 32efcc06d2a1 ("tcp: export count for rehash attempts") Signed-off-by: Eric Dumazet Link: https://patch.msgid.link/20260416200319.3608680-13-edumazet@google.com Signed-off-by: Jakub Kicinski

tcp: annotate data-races around tp->srtt_us

2026-04-18T18:10:13+00:00

tcp_get_timestamping_opt_stats() intentionally runs lockless, we must add READ_ONCE() and WRITE_ONCE() annotations to keep KCSAN happy. Fixes: e8bd8fca6773 ("tcp: add SRTT to SCM_TIMESTAMPING_OPT_STATS") Signed-off-by: Eric Dumazet Link: https://patch.msgid.link/20260416200319.3608680-12-edumazet@google.com Signed-off-by: Jakub Kicinski

tcp: annotate data-races around tp->reord_seen

2026-04-18T18:10:13+00:00

tcp_get_timestamping_opt_stats() intentionally runs lockless, we must add READ_ONCE() and WRITE_ONCE() annotations to keep KCSAN happy. Fixes: 7ec65372ca53 ("tcp: add stat of data packet reordering events") Signed-off-by: Eric Dumazet Link: https://patch.msgid.link/20260416200319.3608680-11-edumazet@google.com Signed-off-by: Jakub Kicinski

tcp: annotate data-races around tp->dsack_dups

2026-04-18T18:10:13+00:00

tcp_get_timestamping_opt_stats() intentionally runs lockless, we must add READ_ONCE() and WRITE_ONCE() annotations to keep KCSAN happy. Fixes: 7e10b6554ff2 ("tcp: add dsack blocks received stats") Signed-off-by: Eric Dumazet Link: https://patch.msgid.link/20260416200319.3608680-10-edumazet@google.com Signed-off-by: Jakub Kicinski

tcp: annotate data-races around tp->bytes_retrans

2026-04-18T18:10:13+00:00

tcp_get_timestamping_opt_stats() intentionally runs lockless, we must add READ_ONCE() and WRITE_ONCE() annotations to keep KCSAN happy. Fixes: fb31c9b9f6c8 ("tcp: add data bytes retransmitted stats") Signed-off-by: Eric Dumazet Link: https://patch.msgid.link/20260416200319.3608680-9-edumazet@google.com Signed-off-by: Jakub Kicinski

tcp: annotate data-races around tp->bytes_sent

2026-04-18T18:10:12+00:00

tcp_get_timestamping_opt_stats() intentionally runs lockless, we must add READ_ONCE() and WRITE_ONCE() annotations to keep KCSAN happy. Fixes: ba113c3aa79a ("tcp: add data bytes sent stats") Signed-off-by: Eric Dumazet Link: https://patch.msgid.link/20260416200319.3608680-8-edumazet@google.com Signed-off-by: Jakub Kicinski