kernel/linux.git/net/mptcp, branch v6.12.101

mptcp: only set DATA_FIN when a mapping is present

2026-08-03T09:17:24+00:00

commit b2ff91b752b0d85e8815e7f44fd85205c4268094 upstream. 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: Greg Kroah-Hartman

mptcp: decrement subflows counter on failed passive join

2026-08-03T09:17:24+00:00

commit f3ca0ee2cc308e33896536789cbc5f3a12ca7b30 upstream. 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: Greg Kroah-Hartman

mptcp: pm: fix extra_subflows underflow on userspace PM subflow creation

2026-06-19T11:42:39+00:00

commit 14e9fea30b68fc75b2b3d97396a7e6adb544bd2a upstream. The userspace PM increments extra_subflows after __mptcp_subflow_connect() succeeds, but __mptcp_subflow_connect() calls mptcp_pm_close_subflow() on failure to roll back the pre-increment done by the kernel PM's fill_*() helpers. Because the userspace PM hasn't incremented yet at that point, this decrement is spurious and causes extra_subflows to underflow. Fix it by aligning the userspace PM with the kernel PM: increment extra_subflows before calling __mptcp_subflow_connect(), so the existing error path in subflow.c correctly rolls it back on failure. Also simplify the error handling by taking pm.lock only when needed for cleanup. Fixes: 77e4b94a3de6 ("mptcp: update userspace pm infos") Cc: stable@vger.kernel.org Signed-off-by: Tao Cui Reviewed-by: Matthieu Baerts (NGI0) Signed-off-by: Matthieu Baerts (NGI0) Link: https://patch.msgid.link/20260602-net-mptcp-misc-fixes-7-1-rc7-v2-5-856831229976@kernel.org Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

mptcp: fix missing wakeups in edge scenarios

2026-06-19T11:42:38+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: add-addr: always drop other suboptions

2026-06-19T11:42:30+00:00

commit bd34fa0257261b76964df1c98f44b3cb4ee14620 upstream. When an ADD_ADDR needs to be sent, it could be prepared if there is enough remaining space and even if the packet is not a pure ACK. But it would be dropped soon after. Indeed, in mptcp_pm_add_addr_signal(), there is enough space to fit a DSS of 20 octets and an ADD_ADDR echo containing an IPv4 address on 8 octets for example. In this case, the packet would be prepared, the MPTCP_ADD_ADDR_ECHO bit would be removed from pm->addr_signal, but the option would be silently dropped in mptcp_established_options_add_addr() not to override DSS info in the union from 'struct mptcp_out_options', and also because mptcp_write_options() will enforce mutually exclusion with DSS. Instead, don't even try to send an ADD_ADDR if it is not a pure ACK. Retry for each new packet until a pure-ACK is emitted. That's fine to do that, because each time an ADD_ADDR (echo) is scheduled, a pure ACK is queued. This also simplifies the code, and the skb checks can be done earlier, before the lock. Note: also, since commit 6d0060f600ad ("mptcp: Write MPTCP DSS headers to outgoing data packets"), opts->ahmac would not have been set to 0 when other suboptions were not dropped, and when sending an ADD_ADDR echo. That would have resulted in sending an ADD_ADDR using garbage info, where there was not enough space, instead of an echo one without the ADD_ADDR HMAC. Fixes: 1bff1e43a30e ("mptcp: optimize out option generation") Cc: stable@vger.kernel.org Signed-off-by: Matthieu Baerts (NGI0) Link: https://patch.msgid.link/20260602-net-mptcp-misc-fixes-7-1-rc7-v2-11-856831229976@kernel.org Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman

mptcp: sockopt: check timestamping ret value

2026-06-19T11:42:30+00:00

commit 57132affbc89c02e1bf73fdf5724311bdc9a29da upstream. sock_set_timestamping() can fail for different reasons. The returned value should then be checked. If sock_set_timestamping() fails for at least one subflow, the first error is now reported to the userspace, similar to what is done with other socket options. Fixes: 9061f24bf82e ("mptcp: sockopt: propagate timestamp request to subflows") Cc: stable@vger.kernel.org Reported-by: Willem de Bruijn Closes: https://lore.kernel.org/willemdebruijn.kernel.178a41a53d041@gmail.com Reviewed-by: Mat Martineau Signed-off-by: Matthieu Baerts (NGI0) Link: https://patch.msgid.link/20260602-net-mptcp-misc-fixes-7-1-rc7-v2-7-856831229976@kernel.org Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman

mptcp: allow subflow rcv wnd to shrink

2026-06-19T11:42:30+00:00

commit da23be77e1292cd611e736c3aa17da633d7ddce7 upstream. In MPTCP connection, the `window` field in the TCP header refers to the MPTCP-level rcv_nxt and it's right edge should not move backward. Such constraint is enforced at DSS option generation time. At the same time, the TCP stack ensures independently that the TCP-level rcv wnd right's edge does not move backward. That in turn causes artificial inflating of the MPTCP rcv window when the incoming data is acked at the TCP level and is OoO in the MPTCP sequence space (or lands in the backlog). As a consequence, the incoming traffic can exceed the receiver rcvbuf size even when the sender is not misbehaving. Prevent such scenario forcibly allowing the TCP subflow to shrink the TCP-level rcv wnd regardless of the current netns setting. Fixes: f3589be0c420 ("mptcp: never shrink offered window") 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-v2-4-856831229976@kernel.org Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman

mptcp: close TOCTOU race while computing rcv_wnd

2026-06-19T11:42:30+00:00

commit 8ab24fdebc369c0dfb90f82c1650b1e66662bb45 upstream. The MPTCP output path access locklessly the MPTCP-level ack_seq in multiple times, using possibly different values for the data_ack in the DSS option and to compute the announced rcv wnd for the same packet. Refactor the cote to avoid inconsistencies which may confuse the peer. Also ensure that the MPTCP level rcv wnd is updated only when the egress packet actually contains a DSS ack. Fixes: fa3fe2b15031 ("mptcp: track window announced to peer") 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-v2-3-856831229976@kernel.org Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman

mptcp: fix retransmission loop when csum is enabled

2026-06-19T11:42:30+00:00

commit d1918b36edcaed0ec4ef6888b2358c6b1ddcff47 upstream. Sashiko noted that retransmission with csum enabled can actually transmit new data, but currently the relevant code does not update accordingly snd_nxt. The may cause incoming ack drop and an endless retransmission loop. Address the issue incrementing snd_nxt as needed. Fixes: 4e14867d5e91 ("mptcp: tune re-injections for csum enabled mode") 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-v2-2-856831229976@kernel.org Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman

mptcp: do not drop partial packets

2026-06-09T10:26:04+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 Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman