kernel/linux.git/net/mptcp/pm_kernel.c, branch v6.18.21

MPTCP: fix lock class name family in pm_nl_create_listen_socket

2026-03-25T10:10:43+00:00

[ Upstream commit 7ab4a7c5d969642782b8a5b608da0dd02aa9f229 ] In mptcp_pm_nl_create_listen_socket(), use entry->addr.family instead of sk->sk_family for lock class setup. The 'sk' parameter is a netlink socket, not the MPTCP subflow socket being created. Fixes: cee4034a3db1 ("mptcp: fix lockdep false positive in mptcp_pm_nl_create_listen_socket()") Signed-off-by: Li Xiasong Reviewed-by: Matthieu Baerts (NGI0) Link: https://patch.msgid.link/20260319112159.3118874-1-lixiasong1@huawei.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin

mptcp: pm: in-kernel: always mark signal+subflow endp as used

2026-03-12T11:09:43+00:00

commit 579a752464a64cb5f9139102f0e6b90a1f595ceb upstream. Syzkaller managed to find a combination of actions that was generating this warning: msk->pm.local_addr_used == 0 WARNING: net/mptcp/pm_kernel.c:1071 at __mark_subflow_endp_available net/mptcp/pm_kernel.c:1071 [inline], CPU#1: syz.2.17/961 WARNING: net/mptcp/pm_kernel.c:1071 at mptcp_nl_remove_subflow_and_signal_addr net/mptcp/pm_kernel.c:1103 [inline], CPU#1: syz.2.17/961 WARNING: net/mptcp/pm_kernel.c:1071 at mptcp_pm_nl_del_addr_doit+0x81d/0x8f0 net/mptcp/pm_kernel.c:1210, CPU#1: syz.2.17/961 Modules linked in: CPU: 1 UID: 0 PID: 961 Comm: syz.2.17 Not tainted 6.19.0-08368-gfafda3b4b06b #22 PREEMPT(full) Hardware name: QEMU Ubuntu 25.10 PC v2 (i440FX + PIIX, + 10.1 machine, 1996), BIOS 1.17.0-debian-1.17.0-1build1 04/01/2014 RIP: 0010:__mark_subflow_endp_available net/mptcp/pm_kernel.c:1071 [inline] RIP: 0010:mptcp_nl_remove_subflow_and_signal_addr net/mptcp/pm_kernel.c:1103 [inline] RIP: 0010:mptcp_pm_nl_del_addr_doit+0x81d/0x8f0 net/mptcp/pm_kernel.c:1210 Code: 89 c5 e8 46 30 6f fe e9 21 fd ff ff 49 83 ed 80 e8 38 30 6f fe 4c 89 ef be 03 00 00 00 e8 db 49 df fe eb ac e8 24 30 6f fe 90 <0f> 0b 90 e9 1d ff ff ff e8 16 30 6f fe eb 05 e8 0f 30 6f fe e8 9a RSP: 0018:ffffc90001663880 EFLAGS: 00010293 RAX: ffffffff82de1a6c RBX: 0000000000000000 RCX: ffff88800722b500 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000 RBP: ffff8880158b22d0 R08: 0000000000010425 R09: ffffffffffffffff R10: ffffffff82de18ba R11: 0000000000000000 R12: ffff88800641a640 R13: ffff8880158b1880 R14: ffff88801ec3c900 R15: ffff88800641a650 FS: 00005555722c3500(0000) GS:ffff8880f909d000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f66346e0f60 CR3: 000000001607c000 CR4: 0000000000350ef0 Call Trace: genl_family_rcv_msg_doit+0x117/0x180 net/netlink/genetlink.c:1115 genl_family_rcv_msg net/netlink/genetlink.c:1195 [inline] genl_rcv_msg+0x3a8/0x3f0 net/netlink/genetlink.c:1210 netlink_rcv_skb+0x16d/0x240 net/netlink/af_netlink.c:2550 genl_rcv+0x28/0x40 net/netlink/genetlink.c:1219 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline] netlink_unicast+0x3e9/0x4c0 net/netlink/af_netlink.c:1344 netlink_sendmsg+0x4aa/0x5b0 net/netlink/af_netlink.c:1894 sock_sendmsg_nosec net/socket.c:727 [inline] __sock_sendmsg+0xc9/0xf0 net/socket.c:742 ____sys_sendmsg+0x272/0x3b0 net/socket.c:2592 ___sys_sendmsg+0x2de/0x320 net/socket.c:2646 __sys_sendmsg net/socket.c:2678 [inline] __do_sys_sendmsg net/socket.c:2683 [inline] __se_sys_sendmsg net/socket.c:2681 [inline] __x64_sys_sendmsg+0x110/0x1a0 net/socket.c:2681 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x143/0x440 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f66346f826d Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007ffc83d8bdc8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 00007f6634985fa0 RCX: 00007f66346f826d RDX: 00000000040000b0 RSI: 0000200000000740 RDI: 0000000000000007 RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00007f6634985fa8 R13: 00007f6634985fac R14: 0000000000000000 R15: 0000000000001770 The actions that caused that seem to be: - Set the MPTCP subflows limit to 0 - Create an MPTCP endpoint with both the 'signal' and 'subflow' flags - Create a new MPTCP connection from a different address: an ADD_ADDR linked to the MPTCP endpoint will be sent ('signal' flag), but no subflows is initiated ('subflow' flag) - Remove the MPTCP endpoint In this case, msk->pm.local_addr_used has been kept to 0 -- because no subflows have been created -- but the corresponding bit in msk->pm.id_avail_bitmap has been cleared when the ADD_ADDR has been sent. This later causes a splat when removing the MPTCP endpoint because msk->pm.local_addr_used has been kept to 0. Now, if an endpoint has both the signal and subflow flags, but it is not possible to create subflows because of the limits or the c-flag case, then the local endpoint counter is still incremented: the endpoint is used at the end. This avoids issues later when removing the endpoint and calling __mark_subflow_endp_available(), which expects msk->pm.local_addr_used to have been previously incremented if the endpoint was marked as used according to msk->pm.id_avail_bitmap. Note that signal_and_subflow variable is reset to false when the limits and the c-flag case allows subflows creation. Also, local_addr_used is only incremented for non ID0 subflows. Fixes: 85df533a787b ("mptcp: pm: do not ignore 'subflow' if 'signal' flag is also set") Cc: stable@vger.kernel.org Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/613 Reviewed-by: Mat Martineau Signed-off-by: Matthieu Baerts (NGI0) Link: https://patch.msgid.link/20260303-net-mptcp-misc-fixes-7-0-rc2-v1-4-4b5462b6f016@kernel.org Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman

mptcp: pm: in-kernel: always set ID as avail when rm endp

2026-03-04T12:21:25+00:00

[ Upstream commit d191101dee25567c2af3b28565f45346c33d65f5 ] Syzkaller managed to find a combination of actions that was generating this warning: WARNING: net/mptcp/pm_kernel.c:1074 at __mark_subflow_endp_available net/mptcp/pm_kernel.c:1074 [inline], CPU#1: syz.7.48/2535 WARNING: net/mptcp/pm_kernel.c:1074 at mptcp_pm_nl_fullmesh net/mptcp/pm_kernel.c:1446 [inline], CPU#1: syz.7.48/2535 WARNING: net/mptcp/pm_kernel.c:1074 at mptcp_pm_nl_set_flags_all net/mptcp/pm_kernel.c:1474 [inline], CPU#1: syz.7.48/2535 WARNING: net/mptcp/pm_kernel.c:1074 at mptcp_pm_nl_set_flags+0x5de/0x640 net/mptcp/pm_kernel.c:1538, CPU#1: syz.7.48/2535 Modules linked in: CPU: 1 UID: 0 PID: 2535 Comm: syz.7.48 Not tainted 6.18.0-03987-gea5f5e676cf5 #17 PREEMPT(voluntary) Hardware name: QEMU Ubuntu 25.10 PC (i440FX + PIIX, 1996), BIOS 1.17.0-debian-1.17.0-1 04/01/2014 RIP: 0010:__mark_subflow_endp_available net/mptcp/pm_kernel.c:1074 [inline] RIP: 0010:mptcp_pm_nl_fullmesh net/mptcp/pm_kernel.c:1446 [inline] RIP: 0010:mptcp_pm_nl_set_flags_all net/mptcp/pm_kernel.c:1474 [inline] RIP: 0010:mptcp_pm_nl_set_flags+0x5de/0x640 net/mptcp/pm_kernel.c:1538 Code: 89 c7 e8 c5 8c 73 fe e9 f7 fd ff ff 49 83 ef 80 e8 b7 8c 73 fe 4c 89 ff be 03 00 00 00 e8 4a 29 e3 fe eb ac e8 a3 8c 73 fe 90 <0f> 0b 90 e9 3d ff ff ff e8 95 8c 73 fe b8 a1 ff ff ff eb 1a e8 89 RSP: 0018:ffffc9001535b820 EFLAGS: 00010287 netdevsim0: tun_chr_ioctl cmd 1074025677 RAX: ffffffff82da294d RBX: 0000000000000001 RCX: 0000000000080000 RDX: ffffc900096d0000 RSI: 00000000000006d6 RDI: 00000000000006d7 netdevsim0: linktype set to 823 RBP: ffff88802cdb2240 R08: 00000000000104ae R09: ffffffffffffffff R10: ffffffff82da27d4 R11: 0000000000000000 R12: 0000000000000000 R13: ffff88801246d8c0 R14: ffffc9001535b8b8 R15: ffff88802cdb1800 FS: 00007fc6ac5a76c0(0000) GS:ffff8880f90c8000(0000) knlGS:0000000000000000 netlink: 'syz.3.50': attribute type 5 has an invalid length. CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 netlink: 1232 bytes leftover after parsing attributes in process `syz.3.50'. CR2: 0000200000010000 CR3: 0000000025b1a000 CR4: 0000000000350ef0 Call Trace: mptcp_pm_set_flags net/mptcp/pm_netlink.c:277 [inline] mptcp_pm_nl_set_flags_doit+0x1d7/0x210 net/mptcp/pm_netlink.c:282 genl_family_rcv_msg_doit+0x117/0x180 net/netlink/genetlink.c:1115 genl_family_rcv_msg net/netlink/genetlink.c:1195 [inline] genl_rcv_msg+0x3a8/0x3f0 net/netlink/genetlink.c:1210 netlink_rcv_skb+0x16d/0x240 net/netlink/af_netlink.c:2550 genl_rcv+0x28/0x40 net/netlink/genetlink.c:1219 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline] netlink_unicast+0x3e9/0x4c0 net/netlink/af_netlink.c:1344 netlink_sendmsg+0x4ab/0x5b0 net/netlink/af_netlink.c:1894 sock_sendmsg_nosec net/socket.c:718 [inline] __sock_sendmsg+0xc9/0xf0 net/socket.c:733 ____sys_sendmsg+0x272/0x3b0 net/socket.c:2608 ___sys_sendmsg+0x2de/0x320 net/socket.c:2662 __sys_sendmsg net/socket.c:2694 [inline] __do_sys_sendmsg net/socket.c:2699 [inline] __se_sys_sendmsg net/socket.c:2697 [inline] __x64_sys_sendmsg+0x110/0x1a0 net/socket.c:2697 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xed/0x360 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fc6adb66f6d Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007fc6ac5a6ff8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 00007fc6addf5fa0 RCX: 00007fc6adb66f6d RDX: 0000000000048084 RSI: 00002000000002c0 RDI: 000000000000000e RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 netlink: 'syz.5.51': attribute type 2 has an invalid length. R13: 00007fff25e91fe0 R14: 00007fc6ac5a7ce4 R15: 00007fff25e920d7 The actions that caused that seem to be: - Create an MPTCP endpoint for address A without any flags - Create a new MPTCP connection from address A - Remove the MPTCP endpoint: the corresponding subflows will be removed - Recreate the endpoint with the same ID, but with the subflow flag - Change the same endpoint to add the fullmesh flag In this case, msk->pm.local_addr_used has been kept to 0 as expected, but the corresponding bit in msk->pm.id_avail_bitmap was still unset after having removed the endpoint, causing the splat later on. When removing an endpoint, the corresponding endpoint ID was only marked as available for "signal" types with an announced address, plus all "subflow" types, but not the other types like an endpoint corresponding to the initial subflow. In these cases, re-creating an endpoint with the same ID didn't signal/create anything. Here, adding the fullmesh flag was creating the splat when calling __mark_subflow_endp_available() from mptcp_pm_nl_fullmesh(), because msk->pm.local_addr_used was set to 0 while the ID was marked as used. To fix this issue, the corresponding bit in msk->pm.id_avail_bitmap can always be set as available when removing an MPTCP in-kernel endpoint. In other words, moving the call to __set_bit() to do it in all cases, except for "subflow" types where this bit is handled in a dedicated helper. Note: instead of adding a new spin_(un)lock_bh that would be taken in all cases, do all the actions requiring the spin lock under the same block. This modification potentially fixes another issue reported by syzbot, see [1]. But without a reproducer or more details about what exactly happened before, it is hard to confirm. Fixes: e255683c06df ("mptcp: pm: re-using ID of unused removed ADD_ADDR") Cc: stable@vger.kernel.org Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/606 Reported-by: syzbot+f56f7d56e2c6e11a01b6@syzkaller.appspotmail.com Closes: https://lore.kernel.org/68fcfc4a.050a0220.346f24.02fb.GAE@google.com [1] Reviewed-by: Mat Martineau Signed-off-by: Matthieu Baerts (NGI0) Link: https://patch.msgid.link/20260205-net-mptcp-misc-fixes-6-19-rc8-v2-1-c2720ce75c34@kernel.org Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin

mptcp: fix race in mptcp_pm_nl_flush_addrs_doit()

2026-02-06T15:57:31+00:00

[ Upstream commit e2a9eeb69f7d4ca4cf4c70463af77664fdb6ab1d ] syzbot and Eulgyu Kim reported crashes in mptcp_pm_nl_get_local_id() and/or mptcp_pm_nl_is_backup() Root cause is list_splice_init() in mptcp_pm_nl_flush_addrs_doit() which is not RCU ready. list_splice_init_rcu() can not be called here while holding pernet->lock spinlock. Many thanks to Eulgyu Kim for providing a repro and testing our patches. Fixes: 141694df6573 ("mptcp: remove address when netlink flushes addrs") Signed-off-by: Eric Dumazet Reported-by: syzbot+5498a510ff9de39d37da@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/6970a46d.a00a0220.3ad28e.5cf0.GAE@google.com/T/ Reported-by: Eulgyu Kim Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/611 Reviewed-by: Mat Martineau Signed-off-by: Matthieu Baerts (NGI0) Link: https://patch.msgid.link/20260124-net-mptcp-race_nl_flush_addrs-v3-1-b2dc1b613e9d@kernel.org Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin

mptcp: fix address removal logic in mptcp_pm_nl_rm_addr

2025-11-20T04:07:15+00:00

Fix inverted WARN_ON_ONCE condition that prevented normal address removal counter updates. The current code only executes decrement logic when the counter is already 0 (abnormal state), while normal removals (counter > 0) are ignored. Signed-off-by: Gang Yan Fixes: 636113918508 ("mptcp: pm: remove '_nl' from mptcp_pm_nl_rm_addr_received") Cc: stable@vger.kernel.org Reviewed-by: Matthieu Baerts (NGI0) Signed-off-by: Matthieu Baerts (NGI0) Link: https://patch.msgid.link/20251118-net-mptcp-misc-fixes-6-18-rc6-v1-10-806d3781c95f@kernel.org Signed-off-by: Jakub Kicinski

mptcp: pm: in-kernel: C-flag: handle late ADD_ADDR

2025-10-22T00:36:45+00:00

The special C-flag case expects the ADD_ADDR to be received when switching to 'fully-established'. But for various reasons, the ADD_ADDR could be sent after the "4th ACK", and the special case doesn't work. On NIPA, the new test validating this special case for the C-flag failed a few times, e.g. 102 default limits, server deny join id 0 syn rx [FAIL] got 0 JOIN[s] syn rx expected 2 Server ns stats (...) MPTcpExtAddAddrTx 1 MPTcpExtEchoAdd 1 Client ns stats (...) MPTcpExtAddAddr 1 MPTcpExtEchoAddTx 1 synack rx [FAIL] got 0 JOIN[s] synack rx expected 2 ack rx [FAIL] got 0 JOIN[s] ack rx expected 2 join Rx [FAIL] see above syn tx [FAIL] got 0 JOIN[s] syn tx expected 2 join Tx [FAIL] see above I had a suspicion about what the issue could be: the ADD_ADDR might have been received after the switch to the 'fully-established' state. The issue was not easy to reproduce. The packet capture shown that the ADD_ADDR can indeed be sent with a delay, and the client would not try to establish subflows to it as expected. A simple fix is not to mark the endpoints as 'used' in the C-flag case, when looking at creating subflows to the remote initial IP address and port. In this case, there is no need to try. Note: newly added fullmesh endpoints will still continue to be used as expected, thanks to the conditions behind mptcp_pm_add_addr_c_flag_case. Fixes: 4b1ff850e0c1 ("mptcp: pm: in-kernel: usable client side with C-flag") Cc: stable@vger.kernel.org Reviewed-by: Geliang Tang Signed-off-by: Matthieu Baerts (NGI0) Link: https://patch.msgid.link/20251020-net-mptcp-c-flag-late-add-addr-v1-1-8207030cb0e8@kernel.org Signed-off-by: Jakub Kicinski

mptcp: pm: in-kernel: add laminar endpoints

2025-09-27T00:44:05+00:00

Currently, upon the reception of an ADD_ADDR (and when the fullmesh flag is not used), the in-kernel PM will create new subflows using the local address the routing configuration will pick. It would be easier to pick local addresses from a selected list of endpoints, and use it only once, than relying on routing rules. Use case: both the client (C) and the server (S) have two addresses (a and b). The client establishes the connection between C(a) and S(a). Once established, the server announces its additional address S(b). Once received, the client connects to it using its second address C(b). Compared to a situation without the 'laminar' endpoint for C(b), the client didn't use this address C(b) to establish a subflow to the server's primary address S(a). So at the end, we have: C S C(a) --- S(a) C(b) --- S(b) In case of a 3rd address on each side (C(c) and S(c)), upon the reception of an ADD_ADDR with S(c), the client should not pick C(b) because it has already been used. C(c) should then be used. Note that this situation is currently possible if C doesn't add any endpoint, but configure the routing in order to pick C(b) for the route to S(b), and pick C(c) for the route to S(c). That doesn't sound very practical because it means knowing in advance the IP addresses that will be used and announced by the server. 'laminar', like the idea of laminar flows: the different subflows don't mix with each other on an endpoint, unlike the "turbulent" way traffic is mixed by 'fullmesh'. In the code, the new endpoint type is added. Similar to the other subflow types, an MPTCP_INFO counter is added. While at it, hole are now commented in struct mptcp_info, to remember next time that these holes can no longer be used. Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/503 Reviewed-by: Mat Martineau Signed-off-by: Matthieu Baerts (NGI0) Link: https://patch.msgid.link/20250925-net-next-mptcp-c-flag-laminar-v1-15-ad126cc47c6b@kernel.org Signed-off-by: Jakub Kicinski

mptcp: pm: in-kernel: compare IDs instead of addresses

2025-09-27T00:44:05+00:00

When receiving an ADD_ADDR right after the 3WHS, the connection will switch to 'fully established'. It means the MPTCP worker will be called to treat two events, in this order: ADD_ADDR_RECEIVED, PM_ESTABLISHED. The MPTCP endpoints cannot have the ID 0, because it is reserved to the address and port used by the initial subflow. To be able to deal with this case in different places, msk->mpc_endpoint_id contains the endpoint ID linked to the initial subflow. This variable was only set when treating the first PM_ESTABLISHED event, after ADD_ADDR_RECEIVED. That's why in fill_local_addresses_vec(), the endpoint addresses were compared with the one of the initial subflow, instead of only comparing the IDs. Instead, msk->mpc_endpoint_id is now set when treating ADD_ADDR_RECEIVED as well, if needed, then the IDs can be compared. To be able to do so, the code doing that is now in a dedicated helper, and called from the functions linked to the two actions. While at it, mptcp_endp_get_local_id() has also been moved up, next to this new helper, because they are linked, and to be able to use it in fill_local_addresses_vec() in the next commit. Reviewed-by: Mat Martineau Signed-off-by: Matthieu Baerts (NGI0) Link: https://patch.msgid.link/20250925-net-next-mptcp-c-flag-laminar-v1-14-ad126cc47c6b@kernel.org Signed-off-by: Jakub Kicinski

mptcp: pm: in-kernel: reduce pernet struct size

2025-09-27T00:44:05+00:00

All the 'unsigned int' variables from the 'pm_nl_pernet' structure are bounded to MPTCP_PM_ADDR_MAX, currently set to 8. The endpoint ID is also bounded by the protocol to 8-bit. MPTCP_PM_ADDR_MAX, if extended later, will never over 8-bit. So no need to use 'unsigned int' variables, 'u8' is enough. Note that the exposed counters in MPTCP_INFO are already limited to 8-bit, same for pm->extra_subflows, and others. So it seems even better to limit them to 8-bit. Reviewed-by: Mat Martineau Signed-off-by: Matthieu Baerts (NGI0) Link: https://patch.msgid.link/20250925-net-next-mptcp-c-flag-laminar-v1-13-ad126cc47c6b@kernel.org Signed-off-by: Jakub Kicinski

mptcp: pm: in-kernel: remove stale_loss_cnt

2025-09-27T00:44:05+00:00

It is currently not used. It was in fact never used since its introduction in commit ff5a0b421cb2 ("mptcp: faster active backup recovery"). It was probably initially added to struct pm_nl_pernet during the development of this commit, before being added to struct mptcp_pernet in ctrl.c, but not removed from the first place. Reviewed-by: Mat Martineau Signed-off-by: Matthieu Baerts (NGI0) Link: https://patch.msgid.link/20250925-net-next-mptcp-c-flag-laminar-v1-12-ad126cc47c6b@kernel.org Signed-off-by: Jakub Kicinski