kernel/linux.git/net/mptcp, branch v5.10.268

mptcp: decrement subflows counter on failed passive join

2026-08-23T12:16:26+00:00

[ Upstream commit f3ca0ee2cc308e33896536789cbc5f3a12ca7b30 ] mptcp_pm_allow_new_subflow() increments extra_subflows before __mptcp_finish_join() on the passive MP_JOIN path. In case of race conditions, the subflow is dropped without calling mptcp_close_ssk(), so the counter is not rolled back. Call mptcp_pm_close_subflow() when the join completion fails to decrement the subflows counter. Fixes: 10f6d46c943d ("mptcp: fix race between MP_JOIN and close") Cc: stable@vger.kernel.org Signed-off-by: Chenguang Zhao Reviewed-by: Matthieu Baerts (NGI0) Signed-off-by: Matthieu Baerts (NGI0) Link: https://patch.msgid.link/20260722-net-mptcp-misc-fixes-7-2-rc5-v1-1-6fb595bc86ef@kernel.org Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

mptcp: fix subflow accounting on close

2026-08-23T12:16:26+00:00

[ Upstream commit 95d686517884a403412b000361cee2b08b2ed1e6 ] If the PM closes a fully established MPJ subflow or the subflow creation errors out in it's early stage the subflows counter is not bumped accordingly. This change adds the missing accounting, additionally taking care of updating accordingly the 'accept_subflow' flag. Fixes: a88c9e496937 ("mptcp: do not block subflows creation on errors") Signed-off-by: Paolo Abeni Signed-off-by: Mat Martineau Signed-off-by: Jakub Kicinski Stable-dep-of: f3ca0ee2cc30 ("mptcp: decrement subflows counter on failed passive join") Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

mptcp: only set DATA_FIN when a mapping is present

2026-08-23T12:16:26+00:00

[ Upstream commit b2ff91b752b0d85e8815e7f44fd85205c4268094 ] mptcp_get_options() clears only the status group of struct mptcp_options_received; data_seq, subflow_seq and data_len are filled in by mptcp_parse_option() exclusively inside the DSS mapping block, which runs only when the DSS M (mapping present) bit is set. A peer can send a DSS option with the DATA_FIN flag set but the mapping bit clear. The parser then records mp_opt->data_fin while leaving data_len and data_seq uninitialized. For a zero-length segment mptcp_incoming_options() evaluates if (mp_opt.data_fin && mp_opt.data_len == 1 && mptcp_update_rcv_data_fin(msk, mp_opt.data_seq, mp_opt.dsn64)) which reads the uninitialized data_len and data_seq; KMSAN reports an uninit-value in mptcp_incoming_options(). The stale data_seq can also be fed into the receive-side DATA_FIN sequence tracking. Record the DATA_FIN flag only when the DSS option carries a mapping, so data_fin is never set without data_seq and data_len also being present. data_fin is part of the status group that mptcp_get_options() clears up front, so on the no-map path it stays zero and the zero-length DATA_FIN branch is simply skipped. A DATA_FIN is always transmitted together with a mapping (mptcp_write_data_fin() sets use_map along with data_seq and data_len), so legitimate DATA_FIN handling is unaffected. Move the pr_debug() that logs the parsed DSS flags below the mapping block, so it reports the final data_fin value instead of the stale one it would otherwise print before the assignment. Fixes: 43b54c6ee382 ("mptcp: Use full MPTCP-level disconnect state machine") Suggested-by: Paolo Abeni Cc: stable@vger.kernel.org Signed-off-by: Michael Bommarito Reviewed-by: Matthieu Baerts (NGI0) Link: https://patch.msgid.link/20260709191925.2811195-1-michael.bommarito@gmail.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

mptcp: options: reset DSS fields in case of unexpected size

2026-08-23T12:16:16+00:00

commit 35772b4981f38ba8059372cde8753e8e477e98ec upstream. A remote peer could send a malformed DSS with a wrong size, followed by another DSS or MPC + Data. In this case, the first suboption will be ignored, but leaving some fields written, which could lead to inconsistency or access uninitialized data. Explicitly reset the fields that could have been modified in case of unexpected size. Link: https://netdev-ai.bots.linux.dev/sashiko/#/patchset/20260728-net-mptcp-misc-fixes-7-2-rc6-v1-0-f7e2d229159d%40kernel.org?part=1 Fixes: 648ef4b88673 ("mptcp: Implement MPTCP receive path") Cc: stable@vger.kernel.org Signed-off-by: Matthieu Baerts (NGI0) Link: https://patch.msgid.link/20260803-net-mptcp-misc-fixes-7-2-rc6-v2-1-b8f496d71664@kernel.org Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman

mptcp: fix missing wakeups in edge scenarios

2026-07-04T11:38:41+00:00

[ Upstream commit 9d8d28738f24b75616d6ca7a27cb4aed88520343 ] The mptcp_recvmsg() can fill MPTCP socket receive queue via mptcp_move_skbs(), but currently does not try to wakeup any listener, because the same process is going to check the receive queue soon. When multiple threads are reading from the same fd, the above can cause stall. Add the missing wakeup. Fixes: 6771bfd9ee24 ("mptcp: update mptcp ack sequence from work queue") Cc: stable@vger.kernel.org Signed-off-by: Paolo Abeni Reviewed-by: Matthieu Baerts (NGI0) Signed-off-by: Matthieu Baerts (NGI0) Link: https://patch.msgid.link/20260602-net-mptcp-misc-fixes-7-1-rc7-v2-1-856831229976@kernel.org Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

mptcp: do not drop partial packets

2026-06-19T11:21:45+00:00

[ Upstream commit 50c2d91c5dfa0e465826ec1f8dbad9cdc254bd85 ] When a packet arrives with map_seq < ack_seq < end_seq, the beginning of the packet has already been acknowledged but the end contains new data. Currently the entire packet is dropped as "old data," forcing the sender to retransmit. Instead, skip the already-acked bytes by adjusting the skb offset and enqueue only the new portion. Update bytes_received and ack_seq to reflect the new data consumed. A previous attempt at this fix has been sent by Paolo Abeni [1], but had issues [2]: it also added a zero-window check and changed rcv_wnd_sent initialization, which caused test regressions. This version addresses only the partial packet handling without modifying receive window accounting. Fixes: ab174ad8ef76 ("mptcp: move ooo skbs into msk out of order queue.") Cc: stable@vger.kernel.org Link: https://lore.kernel.org/c9b426a4e163aa3c4fe8b80c79f1a610f47ae7d8.1763075056.git.pabeni@redhat.com [1] Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/600 [2] Signed-off-by: Shardul Bankar [pabeni@redhat.com: update map] Signed-off-by: Paolo Abeni Reviewed-by: Matthieu Baerts (NGI0) Signed-off-by: Matthieu Baerts (NGI0) Link: https://patch.msgid.link/20260515-net-mptcp-misc-fixes-7-1-rc4-v2-1-701e96419f2f@kernel.org Signed-off-by: Paolo Abeni [ dropped `msk->bytes_received += copy_len;` and relocated the `drop:` label to the function end for the existing RCVPRUNED `goto drop;` ] Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

mptcp: pm: ADD_ADDR rtx: fix potential data-race

2026-06-19T11:21:44+00:00

[ Upstream commit 5cd6e0ad79d2615264f63929f8b457ad97ae550d ] This mptcp_pm_add_timer() helper is executed as a timer callback in softirq context. To avoid any data races, the socket lock needs to be held with bh_lock_sock(). If the socket is in use, retry again soon after, similar to what is done with the keepalive timer. Fixes: 00cfd77b9063 ("mptcp: retransmit ADD_ADDR when timeout") Cc: stable@vger.kernel.org Reviewed-by: Mat Martineau Signed-off-by: Matthieu Baerts (NGI0) Link: https://patch.msgid.link/20260505-net-mptcp-pm-fixes-7-1-rc3-v1-3-fca8091060a4@kernel.org Signed-off-by: Jakub Kicinski [ relocated change from net/mptcp/pm.c to net/mptcp/pm_netlink.c ] Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

mptcp: pm: ignore unknown endpoint flags

2026-01-19T12:12:03+00:00

[ Upstream commit 0ace3297a7301911e52d8195cb1006414897c859 ] Before this patch, the kernel was saving any flags set by the userspace, even unknown ones. This doesn't cause critical issues because the kernel is only looking at specific ones. But on the other hand, endpoints dumps could tell the userspace some recent flags seem to be supported on older kernel versions. Instead, ignore all unknown flags when parsing them. By doing that, the userspace can continue to set unsupported flags, but it has a way to verify what is supported by the kernel. Note that it sounds better to continue accepting unsupported flags not to change the behaviour, but also that eases things on the userspace side by adding "optional" endpoint types only supported by newer kernel versions without having to deal with the different kernel versions. A note for the backports: there will be conflicts in mptcp.h on older versions not having the mentioned flags, the new line should still be added last, and the '5' needs to be adapted to have the same value as the last entry. Fixes: 01cacb00b35c ("mptcp: add netlink-based PM") Cc: stable@vger.kernel.org Reviewed-by: Mat Martineau Signed-off-by: Matthieu Baerts (NGI0) Link: https://patch.msgid.link/20251205-net-mptcp-misc-fixes-6-19-rc1-v1-1-9e4781a6c1b8@kernel.org Signed-off-by: Jakub Kicinski [ GENMASK(5, 0) => GENMASK(2, 0) and applied fix to mptcp_pm_parse_addr() ] Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

mptcp: Fix proto fallback detection with BPF

2025-12-06T21:08:24+00:00

commit c77b3b79a92e3345aa1ee296180d1af4e7031f8f upstream. The sockmap feature allows bpf syscall from userspace, or based on bpf sockops, replacing the sk_prot of sockets during protocol stack processing with sockmap's custom read/write interfaces. ''' tcp_rcv_state_process() syn_recv_sock()/subflow_syn_recv_sock() tcp_init_transfer(BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB) bpf_skops_established <== sockops bpf_sock_map_update(sk) <== call bpf helper tcp_bpf_update_proto() <== update sk_prot ''' When the server has MPTCP enabled but the client sends a TCP SYN without MPTCP, subflow_syn_recv_sock() performs a fallback on the subflow, replacing the subflow sk's sk_prot with the native sk_prot. ''' subflow_syn_recv_sock() subflow_ulp_fallback() subflow_drop_ctx() mptcp_subflow_ops_undo_override() ''' Then, this subflow can be normally used by sockmap, which replaces the native sk_prot with sockmap's custom sk_prot. The issue occurs when the user executes accept::mptcp_stream_accept::mptcp_fallback_tcp_ops(). Here, it uses sk->sk_prot to compare with the native sk_prot, but this is incorrect when sockmap is used, as we may incorrectly set sk->sk_socket->ops. This fix uses the more generic sk_family for the comparison instead. Additionally, this also prevents a WARNING from occurring: result from ./scripts/decode_stacktrace.sh: ------------[ cut here ]------------ WARNING: CPU: 0 PID: 337 at net/mptcp/protocol.c:68 mptcp_stream_accept \ (net/mptcp/protocol.c:4005) Modules linked in: ... PKRU: 55555554 Call Trace: do_accept (net/socket.c:1989) __sys_accept4 (net/socket.c:2028 net/socket.c:2057) __x64_sys_accept (net/socket.c:2067) x64_sys_call (arch/x86/entry/syscall_64.c:41) do_syscall_64 (arch/x86/entry/syscall_64.c:63 arch/x86/entry/syscall_64.c:94) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130) RIP: 0033:0x7f87ac92b83d ---[ end trace 0000000000000000 ]--- Fixes: 0b4f33def7bb ("mptcp: fix tcp fallback crash") Signed-off-by: Jiayuan Chen Signed-off-by: Martin KaFai Lau Reviewed-by: Jakub Sitnicki Reviewed-by: Matthieu Baerts (NGI0) Cc: Link: https://patch.msgid.link/20251111060307.194196-3-jiayuan.chen@linux.dev [ Conflicts in protocol.c, because commit 8e2b8a9fa512 ("mptcp: don't overwrite sock_ops in mptcp_is_tcpsk()") is not in this version. It changes the logic on how and where the sock_ops is overridden in case of passive fallback. To fix this, mptcp_is_tcpsk() is modified to use the family, but first, a check of the protocol is required to continue returning 'false' in case of MPTCP socket. ] Signed-off-by: Matthieu Baerts (NGI0) Signed-off-by: Greg Kroah-Hartman

mptcp: do not fallback when OoO is present

2025-12-06T21:08:21+00:00

[ Upstream commit 1bba3f219c5e8c29e63afa3c1fc24f875ebec119 ] In case of DSS corruption, the MPTCP protocol tries to avoid the subflow reset if fallback is possible. Such corruptions happen in the receive path; to ensure fallback is possible the stack additionally needs to check for OoO data, otherwise the fallback will break the data stream. Fixes: e32d262c89e2 ("mptcp: handle consistently DSS corruption") Cc: stable@vger.kernel.org Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/598 Signed-off-by: Paolo Abeni Reviewed-by: Matthieu Baerts (NGI0) Signed-off-by: Matthieu Baerts (NGI0) Link: https://patch.msgid.link/20251118-net-mptcp-misc-fixes-6-18-rc6-v1-4-806d3781c95f@kernel.org Signed-off-by: Jakub Kicinski [ patch mptcp_dss_corruption() ] Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman