kernel/linux.git/net/mptcp/ctrl.c, branch v6.12.80

mptcp: reset blackhole on success with non-loopback ifaces

2025-10-23T14:20:46+00:00

[ Upstream commit 833d4313bc1e9e194814917d23e8874d6b651649 ] When a first MPTCP connection gets successfully established after a blackhole period, 'active_disable_times' was supposed to be reset when this connection was done via any non-loopback interfaces. Unfortunately, the opposite condition was checked: only reset when the connection was established via a loopback interface. Fixing this by simply looking at the opposite. This is similar to what is done with TCP FastOpen, see tcp_fastopen_active_disable_ofo_check(). This patch is a follow-up of a previous discussion linked to commit 893c49a78d9f ("mptcp: Use __sk_dst_get() and dst_dev_rcu() in mptcp_active_enable()."), see [1]. Fixes: 27069e7cb3d1 ("mptcp: disable active MPTCP in case of blackhole") Cc: stable@vger.kernel.org Link: https://lore.kernel.org/4209a283-8822-47bd-95b7-87e96d9b7ea3@kernel.org [1] Signed-off-by: Matthieu Baerts (NGI0) Reviewed-by: Simon Horman Reviewed-by: Kuniyuki Iwashima Link: https://patch.msgid.link/20250918-net-next-mptcp-blackhole-reset-loopback-v1-1-bf5818326639@kernel.org Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

mptcp: Use __sk_dst_get() and dst_dev_rcu() in mptcp_active_enable().

2025-10-23T14:20:46+00:00

[ Upstream commit 893c49a78d9f85e4b8081b908fb7c407d018106a ] mptcp_active_enable() is called from subflow_finish_connect(), which is icsk->icsk_af_ops->sk_rx_dst_set() and it's not always under RCU. Using sk_dst_get(sk)->dev could trigger UAF. Let's use __sk_dst_get() and dst_dev_rcu(). Fixes: 27069e7cb3d1 ("mptcp: disable active MPTCP in case of blackhole") Signed-off-by: Kuniyuki Iwashima Reviewed-by: Matthieu Baerts (NGI0) Reviewed-by: Eric Dumazet Link: https://patch.msgid.link/20250916214758.650211-8-kuniyu@google.com Signed-off-by: Jakub Kicinski Stable-dep-of: 833d4313bc1e ("mptcp: reset blackhole on success with non-loopback ifaces") Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

mptcp: Call dst_release() in mptcp_active_enable().

2025-10-23T14:20:46+00:00

[ Upstream commit 108a86c71c93ff28087994e6107bc99ebe336629 ] mptcp_active_enable() calls sk_dst_get(), which returns dst with its refcount bumped, but forgot dst_release(). Let's add missing dst_release(). Cc: stable@vger.kernel.org Fixes: 27069e7cb3d1 ("mptcp: disable active MPTCP in case of blackhole") Signed-off-by: Kuniyuki Iwashima Reviewed-by: Matthieu Baerts (NGI0) Reviewed-by: Eric Dumazet Link: https://patch.msgid.link/20250916214758.650211-7-kuniyu@google.com Signed-off-by: Jakub Kicinski Stable-dep-of: 833d4313bc1e ("mptcp: reset blackhole on success with non-loopback ifaces") Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

mptcp: blackhole only if 1st SYN retrans w/o MPC is accepted

2025-02-08T08:58:16+00:00

commit e598d8981fd34470b78a1ae777dbf131b15d5bf2 upstream. The Fixes commit mentioned this: > An MPTCP firewall blackhole can be detected if the following SYN > retransmission after a fallback to "plain" TCP is accepted. But in fact, this blackhole was detected if any following SYN retransmissions after a fallback to TCP was accepted. That's because 'mptcp_subflow_early_fallback()' will set 'request_mptcp' to 0, and 'mpc_drop' will never be reset to 0 after. This is an issue, because some not so unusual situations might cause the kernel to detect a false-positive blackhole, e.g. a client trying to connect to a server while the network is not ready yet, causing a few SYN retransmissions, before reaching the end server. Fixes: 27069e7cb3d1 ("mptcp: disable active MPTCP in case of blackhole") Cc: stable@vger.kernel.org Reviewed-by: Mat Martineau Signed-off-by: Matthieu Baerts (NGI0) Signed-off-by: Paolo Abeni Signed-off-by: Greg Kroah-Hartman

mptcp: sysctl: blackhole timeout: avoid using current->nsproxy

2025-01-17T12:40:46+00:00

commit 92cf7a51bdae24a32c592adcdd59a773ae149289 upstream. As mentioned in the previous commit, using the 'net' structure via 'current' is not recommended for different reasons: - Inconsistency: getting info from the reader's/writer's netns vs only from the opener's netns. - current->nsproxy can be NULL in some cases, resulting in an 'Oops' (null-ptr-deref), e.g. when the current task is exiting, as spotted by syzbot [1] using acct(2). The 'pernet' structure can be obtained from the table->data using container_of(). Fixes: 27069e7cb3d1 ("mptcp: disable active MPTCP in case of blackhole") Cc: stable@vger.kernel.org Link: https://lore.kernel.org/67769ecb.050a0220.3a8527.003f.GAE@google.com [1] Suggested-by: Al Viro Reviewed-by: Mat Martineau Signed-off-by: Matthieu Baerts (NGI0) Link: https://patch.msgid.link/20250108-net-sysctl-current-nsproxy-v1-3-5df34b2083e8@kernel.org Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman

mptcp: sysctl: sched: avoid using current->nsproxy

2025-01-17T12:40:46+00:00

commit d38e26e36206ae3d544d496513212ae931d1da0a upstream. Using the 'net' structure via 'current' is not recommended for different reasons. First, if the goal is to use it to read or write per-netns data, this is inconsistent with how the "generic" sysctl entries are doing: directly by only using pointers set to the table entry, e.g. table->data. Linked to that, the per-netns data should always be obtained from the table linked to the netns it had been created for, which may not coincide with the reader's or writer's netns. Another reason is that access to current->nsproxy->netns can oops if attempted when current->nsproxy had been dropped when the current task is exiting. This is what syzbot found, when using acct(2): Oops: general protection fault, probably for non-canonical address 0xdffffc0000000005: 0000 [#1] PREEMPT SMP KASAN PTI KASAN: null-ptr-deref in range [0x0000000000000028-0x000000000000002f] CPU: 1 UID: 0 PID: 5924 Comm: syz-executor Not tainted 6.13.0-rc5-syzkaller-00004-gccb98ccef0e5 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024 RIP: 0010:proc_scheduler+0xc6/0x3c0 net/mptcp/ctrl.c:125 Code: 03 42 80 3c 38 00 0f 85 fe 02 00 00 4d 8b a4 24 08 09 00 00 48 b8 00 00 00 00 00 fc ff df 49 8d 7c 24 28 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 cc 02 00 00 4d 8b 7c 24 28 48 8d 84 24 c8 00 00 RSP: 0018:ffffc900034774e8 EFLAGS: 00010206 RAX: dffffc0000000000 RBX: 1ffff9200068ee9e RCX: ffffc90003477620 RDX: 0000000000000005 RSI: ffffffff8b08f91e RDI: 0000000000000028 RBP: 0000000000000001 R08: ffffc90003477710 R09: 0000000000000040 R10: 0000000000000040 R11: 00000000726f7475 R12: 0000000000000000 R13: ffffc90003477620 R14: ffffc90003477710 R15: dffffc0000000000 FS: 0000000000000000(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fee3cd452d8 CR3: 000000007d116000 CR4: 00000000003526f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: proc_sys_call_handler+0x403/0x5d0 fs/proc/proc_sysctl.c:601 __kernel_write_iter+0x318/0xa80 fs/read_write.c:612 __kernel_write+0xf6/0x140 fs/read_write.c:632 do_acct_process+0xcb0/0x14a0 kernel/acct.c:539 acct_pin_kill+0x2d/0x100 kernel/acct.c:192 pin_kill+0x194/0x7c0 fs/fs_pin.c:44 mnt_pin_kill+0x61/0x1e0 fs/fs_pin.c:81 cleanup_mnt+0x3ac/0x450 fs/namespace.c:1366 task_work_run+0x14e/0x250 kernel/task_work.c:239 exit_task_work include/linux/task_work.h:43 [inline] do_exit+0xad8/0x2d70 kernel/exit.c:938 do_group_exit+0xd3/0x2a0 kernel/exit.c:1087 get_signal+0x2576/0x2610 kernel/signal.c:3017 arch_do_signal_or_restart+0x90/0x7e0 arch/x86/kernel/signal.c:337 exit_to_user_mode_loop kernel/entry/common.c:111 [inline] exit_to_user_mode_prepare include/linux/entry-common.h:329 [inline] __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline] syscall_exit_to_user_mode+0x150/0x2a0 kernel/entry/common.c:218 do_syscall_64+0xda/0x250 arch/x86/entry/common.c:89 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fee3cb87a6a Code: Unable to access opcode bytes at 0x7fee3cb87a40. RSP: 002b:00007fffcccac688 EFLAGS: 00000202 ORIG_RAX: 0000000000000037 RAX: 0000000000000000 RBX: 00007fffcccac710 RCX: 00007fee3cb87a6a RDX: 0000000000000041 RSI: 0000000000000000 RDI: 0000000000000003 RBP: 0000000000000003 R08: 00007fffcccac6ac R09: 00007fffcccacac7 R10: 00007fffcccac710 R11: 0000000000000202 R12: 00007fee3cd49500 R13: 00007fffcccac6ac R14: 0000000000000000 R15: 00007fee3cd4b000 Modules linked in: ---[ end trace 0000000000000000 ]--- RIP: 0010:proc_scheduler+0xc6/0x3c0 net/mptcp/ctrl.c:125 Code: 03 42 80 3c 38 00 0f 85 fe 02 00 00 4d 8b a4 24 08 09 00 00 48 b8 00 00 00 00 00 fc ff df 49 8d 7c 24 28 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 cc 02 00 00 4d 8b 7c 24 28 48 8d 84 24 c8 00 00 RSP: 0018:ffffc900034774e8 EFLAGS: 00010206 RAX: dffffc0000000000 RBX: 1ffff9200068ee9e RCX: ffffc90003477620 RDX: 0000000000000005 RSI: ffffffff8b08f91e RDI: 0000000000000028 RBP: 0000000000000001 R08: ffffc90003477710 R09: 0000000000000040 R10: 0000000000000040 R11: 00000000726f7475 R12: 0000000000000000 R13: ffffc90003477620 R14: ffffc90003477710 R15: dffffc0000000000 FS: 0000000000000000(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fee3cd452d8 CR3: 000000007d116000 CR4: 00000000003526f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 ---------------- Code disassembly (best guess), 1 bytes skipped: 0: 42 80 3c 38 00 cmpb $0x0,(%rax,%r15,1) 5: 0f 85 fe 02 00 00 jne 0x309 b: 4d 8b a4 24 08 09 00 mov 0x908(%r12),%r12 12: 00 13: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax 1a: fc ff df 1d: 49 8d 7c 24 28 lea 0x28(%r12),%rdi 22: 48 89 fa mov %rdi,%rdx 25: 48 c1 ea 03 shr $0x3,%rdx * 29: 80 3c 02 00 cmpb $0x0,(%rdx,%rax,1) <-- trapping instruction 2d: 0f 85 cc 02 00 00 jne 0x2ff 33: 4d 8b 7c 24 28 mov 0x28(%r12),%r15 38: 48 rex.W 39: 8d .byte 0x8d 3a: 84 24 c8 test %ah,(%rax,%rcx,8) Here with 'net.mptcp.scheduler', the 'net' structure is not really needed, because the table->data already has a pointer to the current scheduler, the only thing needed from the per-netns data. Simply use 'data', instead of getting (most of the time) the same thing, but from a longer and indirect way. Fixes: 6963c508fd7a ("mptcp: only allow set existing scheduler for net.mptcp.scheduler") Cc: stable@vger.kernel.org Reported-by: syzbot+e364f774c6f57f2c86d1@syzkaller.appspotmail.com Closes: https://lore.kernel.org/67769ecb.050a0220.3a8527.003f.GAE@google.com Suggested-by: Al Viro Reviewed-by: Mat Martineau Signed-off-by: Matthieu Baerts (NGI0) Link: https://patch.msgid.link/20250108-net-sysctl-current-nsproxy-v1-2-5df34b2083e8@kernel.org Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman

mptcp: sysctl: avail sched: remove write access

2025-01-17T12:40:46+00:00

commit 771ec78dc8b48d562e6015bb535ed3cd37043d78 upstream. 'net.mptcp.available_schedulers' sysctl knob is there to list available schedulers, not to modify this list. There are then no reasons to give write access to it. Nothing would have been written anyway, but no errors would have been returned, which is unexpected. Fixes: 73c900aa3660 ("mptcp: add net.mptcp.available_schedulers") Cc: stable@vger.kernel.org Reviewed-by: Mat Martineau Signed-off-by: Matthieu Baerts (NGI0) Reviewed-by: Eric Dumazet Link: https://patch.msgid.link/20250108-net-sysctl-current-nsproxy-v1-1-5df34b2083e8@kernel.org Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman

mptcp: disable active MPTCP in case of blackhole

2024-09-11T22:57:50+00:00

An MPTCP firewall blackhole can be detected if the following SYN retransmission after a fallback to "plain" TCP is accepted. In case of blackhole, a similar technique to the one in place with TFO is now used: MPTCP can be disabled for a certain period of time, 1h by default. This time period will grow exponentially when more blackhole issues get detected right after MPTCP is re-enabled and will reset to the initial value when the blackhole issue goes away. The blackhole period can be modified thanks to a new sysctl knob: blackhole_timeout. Two new MIB counters help understanding what's happening: - 'Blackhole', incremented when a blackhole is detected. - 'MPCapableSYNTXDisabled', incremented when an MPTCP connection directly falls back to TCP during the blackhole period. Because the technique is inspired by the one used by TFO, an important part of the new code is similar to what can find in tcp_fastopen.c, with some adaptations to the MPTCP case. Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/57 Signed-off-by: Matthieu Baerts (NGI0) Link: https://patch.msgid.link/20240909-net-next-mptcp-fallback-x-mpc-v1-3-da7ebb4cd2a3@kernel.org Signed-off-by: Jakub Kicinski

mptcp: fallback to TCP after SYN+MPC drops

2024-09-11T22:57:50+00:00

Some middleboxes might be nasty with MPTCP, and decide to drop packets with MPTCP options, instead of just dropping the MPTCP options (or letting them pass...). In this case, it sounds better to fallback to "plain" TCP after 2 retransmissions, and try again. Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/477 Signed-off-by: Matthieu Baerts (NGI0) Reviewed-by: Eric Dumazet Link: https://patch.msgid.link/20240909-net-next-mptcp-fallback-x-mpc-v1-2-da7ebb4cd2a3@kernel.org Signed-off-by: Jakub Kicinski

sysctl: treewide: constify the ctl_table argument of proc_handlers

2024-07-24T18:59:29+00:00

const qualify the struct ctl_table argument in the proc_handler function signatures. This is a prerequisite to moving the static ctl_table structs into .rodata data which will ensure that proc_handler function pointers cannot be modified. This patch has been generated by the following coccinelle script: ``` virtual patch @r1@ identifier ctl, write, buffer, lenp, ppos; identifier func !~ "appldata_(timer|interval)_handler|sched_(rt|rr)_handler|rds_tcp_skbuf_handler|proc_sctp_do_(hmac_alg|rto_min|rto_max|udp_port|alpha_beta|auth|probe_interval)"; @@ int func( - struct ctl_table *ctl + const struct ctl_table *ctl ,int write, void *buffer, size_t *lenp, loff_t *ppos); @r2@ identifier func, ctl, write, buffer, lenp, ppos; @@ int func( - struct ctl_table *ctl + const struct ctl_table *ctl ,int write, void *buffer, size_t *lenp, loff_t *ppos) { ... } @r3@ identifier func; @@ int func( - struct ctl_table * + const struct ctl_table * ,int , void *, size_t *, loff_t *); @r4@ identifier func, ctl; @@ int func( - struct ctl_table *ctl + const struct ctl_table *ctl ,int , void *, size_t *, loff_t *); @r5@ identifier func, write, buffer, lenp, ppos; @@ int func( - struct ctl_table * + const struct ctl_table * ,int write, void *buffer, size_t *lenp, loff_t *ppos); ``` * Code formatting was adjusted in xfs_sysctl.c to comply with code conventions. The xfs_stats_clear_proc_handler, xfs_panic_mask_proc_handler and xfs_deprecated_dointvec_minmax where adjusted. * The ctl_table argument in proc_watchdog_common was const qualified. This is called from a proc_handler itself and is calling back into another proc_handler, making it necessary to change it as part of the proc_handler migration. Co-developed-by: Thomas Weißschuh Signed-off-by: Thomas Weißschuh Co-developed-by: Joel Granados Signed-off-by: Joel Granados