--- /dev/null
+From 3d041393ea8c815f773020fb4a995331a69c0139 Mon Sep 17 00:00:00 2001
+From: Paolo Abeni <pabeni@redhat.com>
+Date: Mon, 14 Oct 2024 16:06:00 +0200
+Subject: mptcp: prevent MPC handshake on port-based signal endpoints
+
+From: Paolo Abeni <pabeni@redhat.com>
+
+commit 3d041393ea8c815f773020fb4a995331a69c0139 upstream.
+
+Syzkaller reported a lockdep splat:
+
+ ============================================
+ WARNING: possible recursive locking detected
+ 6.11.0-rc6-syzkaller-00019-g67784a74e258 #0 Not tainted
+ --------------------------------------------
+ syz-executor364/5113 is trying to acquire lock:
+ ffff8880449f1958 (k-slock-AF_INET){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:351 [inline]
+ ffff8880449f1958 (k-slock-AF_INET){+.-.}-{2:2}, at: sk_clone_lock+0x2cd/0xf40 net/core/sock.c:2328
+
+ but task is already holding lock:
+ ffff88803fe3cb58 (k-slock-AF_INET){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:351 [inline]
+ ffff88803fe3cb58 (k-slock-AF_INET){+.-.}-{2:2}, at: sk_clone_lock+0x2cd/0xf40 net/core/sock.c:2328
+
+ other info that might help us debug this:
+ Possible unsafe locking scenario:
+
+ CPU0
+ ----
+ lock(k-slock-AF_INET);
+ lock(k-slock-AF_INET);
+
+ *** DEADLOCK ***
+
+ May be due to missing lock nesting notation
+
+ 7 locks held by syz-executor364/5113:
+ #0: ffff8880449f0e18 (sk_lock-AF_INET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1607 [inline]
+ #0: ffff8880449f0e18 (sk_lock-AF_INET){+.+.}-{0:0}, at: mptcp_sendmsg+0x153/0x1b10 net/mptcp/protocol.c:1806
+ #1: ffff88803fe39ad8 (k-sk_lock-AF_INET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1607 [inline]
+ #1: ffff88803fe39ad8 (k-sk_lock-AF_INET){+.+.}-{0:0}, at: mptcp_sendmsg_fastopen+0x11f/0x530 net/mptcp/protocol.c:1727
+ #2: ffffffff8e938320 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:326 [inline]
+ #2: ffffffff8e938320 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:838 [inline]
+ #2: ffffffff8e938320 (rcu_read_lock){....}-{1:2}, at: __ip_queue_xmit+0x5f/0x1b80 net/ipv4/ip_output.c:470
+ #3: ffffffff8e938320 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:326 [inline]
+ #3: ffffffff8e938320 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:838 [inline]
+ #3: ffffffff8e938320 (rcu_read_lock){....}-{1:2}, at: ip_finish_output2+0x45f/0x1390 net/ipv4/ip_output.c:228
+ #4: ffffffff8e938320 (rcu_read_lock){....}-{1:2}, at: local_lock_acquire include/linux/local_lock_internal.h:29 [inline]
+ #4: ffffffff8e938320 (rcu_read_lock){....}-{1:2}, at: process_backlog+0x33b/0x15b0 net/core/dev.c:6104
+ #5: ffffffff8e938320 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:326 [inline]
+ #5: ffffffff8e938320 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:838 [inline]
+ #5: ffffffff8e938320 (rcu_read_lock){....}-{1:2}, at: ip_local_deliver_finish+0x230/0x5f0 net/ipv4/ip_input.c:232
+ #6: ffff88803fe3cb58 (k-slock-AF_INET){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:351 [inline]
+ #6: ffff88803fe3cb58 (k-slock-AF_INET){+.-.}-{2:2}, at: sk_clone_lock+0x2cd/0xf40 net/core/sock.c:2328
+
+ stack backtrace:
+ CPU: 0 UID: 0 PID: 5113 Comm: syz-executor364 Not tainted 6.11.0-rc6-syzkaller-00019-g67784a74e258 #0
+ Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
+ Call Trace:
+ <IRQ>
+ __dump_stack lib/dump_stack.c:93 [inline]
+ dump_stack_lvl+0x241/0x360 lib/dump_stack.c:119
+ check_deadlock kernel/locking/lockdep.c:3061 [inline]
+ validate_chain+0x15d3/0x5900 kernel/locking/lockdep.c:3855
+ __lock_acquire+0x137a/0x2040 kernel/locking/lockdep.c:5142
+ lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5759
+ __raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
+ _raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154
+ spin_lock include/linux/spinlock.h:351 [inline]
+ sk_clone_lock+0x2cd/0xf40 net/core/sock.c:2328
+ mptcp_sk_clone_init+0x32/0x13c0 net/mptcp/protocol.c:3279
+ subflow_syn_recv_sock+0x931/0x1920 net/mptcp/subflow.c:874
+ tcp_check_req+0xfe4/0x1a20 net/ipv4/tcp_minisocks.c:853
+ tcp_v4_rcv+0x1c3e/0x37f0 net/ipv4/tcp_ipv4.c:2267
+ ip_protocol_deliver_rcu+0x22e/0x440 net/ipv4/ip_input.c:205
+ ip_local_deliver_finish+0x341/0x5f0 net/ipv4/ip_input.c:233
+ NF_HOOK+0x3a4/0x450 include/linux/netfilter.h:314
+ NF_HOOK+0x3a4/0x450 include/linux/netfilter.h:314
+ __netif_receive_skb_one_core net/core/dev.c:5661 [inline]
+ __netif_receive_skb+0x2bf/0x650 net/core/dev.c:5775
+ process_backlog+0x662/0x15b0 net/core/dev.c:6108
+ __napi_poll+0xcb/0x490 net/core/dev.c:6772
+ napi_poll net/core/dev.c:6841 [inline]
+ net_rx_action+0x89b/0x1240 net/core/dev.c:6963
+ handle_softirqs+0x2c4/0x970 kernel/softirq.c:554
+ do_softirq+0x11b/0x1e0 kernel/softirq.c:455
+ </IRQ>
+ <TASK>
+ __local_bh_enable_ip+0x1bb/0x200 kernel/softirq.c:382
+ local_bh_enable include/linux/bottom_half.h:33 [inline]
+ rcu_read_unlock_bh include/linux/rcupdate.h:908 [inline]
+ __dev_queue_xmit+0x1763/0x3e90 net/core/dev.c:4450
+ dev_queue_xmit include/linux/netdevice.h:3105 [inline]
+ neigh_hh_output include/net/neighbour.h:526 [inline]
+ neigh_output include/net/neighbour.h:540 [inline]
+ ip_finish_output2+0xd41/0x1390 net/ipv4/ip_output.c:235
+ ip_local_out net/ipv4/ip_output.c:129 [inline]
+ __ip_queue_xmit+0x118c/0x1b80 net/ipv4/ip_output.c:535
+ __tcp_transmit_skb+0x2544/0x3b30 net/ipv4/tcp_output.c:1466
+ tcp_rcv_synsent_state_process net/ipv4/tcp_input.c:6542 [inline]
+ tcp_rcv_state_process+0x2c32/0x4570 net/ipv4/tcp_input.c:6729
+ tcp_v4_do_rcv+0x77d/0xc70 net/ipv4/tcp_ipv4.c:1934
+ sk_backlog_rcv include/net/sock.h:1111 [inline]
+ __release_sock+0x214/0x350 net/core/sock.c:3004
+ release_sock+0x61/0x1f0 net/core/sock.c:3558
+ mptcp_sendmsg_fastopen+0x1ad/0x530 net/mptcp/protocol.c:1733
+ mptcp_sendmsg+0x1884/0x1b10 net/mptcp/protocol.c:1812
+ sock_sendmsg_nosec net/socket.c:730 [inline]
+ __sock_sendmsg+0x1a6/0x270 net/socket.c:745
+ ____sys_sendmsg+0x525/0x7d0 net/socket.c:2597
+ ___sys_sendmsg net/socket.c:2651 [inline]
+ __sys_sendmmsg+0x3b2/0x740 net/socket.c:2737
+ __do_sys_sendmmsg net/socket.c:2766 [inline]
+ __se_sys_sendmmsg net/socket.c:2763 [inline]
+ __x64_sys_sendmmsg+0xa0/0xb0 net/socket.c:2763
+ do_syscall_x64 arch/x86/entry/common.c:52 [inline]
+ do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
+ entry_SYSCALL_64_after_hwframe+0x77/0x7f
+ RIP: 0033:0x7f04fb13a6b9
+ Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 01 1a 00 00 90 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 b8 ff ff ff f7 d8 64 89 01 48
+ RSP: 002b:00007ffd651f42d8 EFLAGS: 00000246 ORIG_RAX: 0000000000000133
+ RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007f04fb13a6b9
+ RDX: 0000000000000001 RSI: 0000000020000d00 RDI: 0000000000000004
+ RBP: 00007ffd651f4310 R08: 0000000000000001 R09: 0000000000000001
+ R10: 0000000020000080 R11: 0000000000000246 R12: 00000000000f4240
+ R13: 00007f04fb187449 R14: 00007ffd651f42f4 R15: 00007ffd651f4300
+ </TASK>
+
+As noted by Cong Wang, the splat is false positive, but the code
+path leading to the report is an unexpected one: a client is
+attempting an MPC handshake towards the in-kernel listener created
+by the in-kernel PM for a port based signal endpoint.
+
+Such connection will be never accepted; many of them can make the
+listener queue full and preventing the creation of MPJ subflow via
+such listener - its intended role.
+
+Explicitly detect this scenario at initial-syn time and drop the
+incoming MPC request.
+
+Fixes: 1729cf186d8a ("mptcp: create the listening socket for new port")
+Cc: stable@vger.kernel.org
+Reported-by: syzbot+f4aacdfef2c6a6529c3e@syzkaller.appspotmail.com
+Closes: https://syzkaller.appspot.com/bug?extid=f4aacdfef2c6a6529c3e
+Cc: Cong Wang <cong.wang@bytedance.com>
+Signed-off-by: Paolo Abeni <pabeni@redhat.com>
+Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
+Reviewed-by: Mat Martineau <martineau@kernel.org>
+Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
+Link: https://patch.msgid.link/20241014-net-mptcp-mpc-port-endp-v2-1-7faea8e6b6ae@kernel.org
+Signed-off-by: Jakub Kicinski <kuba@kernel.org>
+[ Conflicts in mib.[ch], because commit 6982826fe5e5 ("mptcp: fallback
+ to TCP after SYN+MPC drops"), and commit 27069e7cb3d1 ("mptcp: disable
+ active MPTCP in case of blackhole") are linked to new features, not
+ available in this version. Resolving the conflicts is easy, simply
+ adding the new lines declaring the new "endpoint attempt" MIB entry. ]
+Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+---
+ net/mptcp/mib.c | 1 +
+ net/mptcp/mib.h | 1 +
+ net/mptcp/pm_netlink.c | 1 +
+ net/mptcp/protocol.h | 1 +
+ net/mptcp/subflow.c | 11 +++++++++++
+ 5 files changed, 15 insertions(+)
+
+--- a/net/mptcp/mib.c
++++ b/net/mptcp/mib.c
+@@ -15,6 +15,7 @@ static const struct snmp_mib mptcp_snmp_
+ SNMP_MIB_ITEM("MPCapableACKRX", MPTCP_MIB_MPCAPABLEPASSIVEACK),
+ SNMP_MIB_ITEM("MPCapableFallbackACK", MPTCP_MIB_MPCAPABLEPASSIVEFALLBACK),
+ SNMP_MIB_ITEM("MPCapableFallbackSYNACK", MPTCP_MIB_MPCAPABLEACTIVEFALLBACK),
++ SNMP_MIB_ITEM("MPCapableEndpAttempt", MPTCP_MIB_MPCAPABLEENDPATTEMPT),
+ SNMP_MIB_ITEM("MPFallbackTokenInit", MPTCP_MIB_TOKENFALLBACKINIT),
+ SNMP_MIB_ITEM("MPTCPRetrans", MPTCP_MIB_RETRANSSEGS),
+ SNMP_MIB_ITEM("MPJoinNoTokenFound", MPTCP_MIB_JOINNOTOKEN),
+--- a/net/mptcp/mib.h
++++ b/net/mptcp/mib.h
+@@ -8,6 +8,7 @@ enum linux_mptcp_mib_field {
+ MPTCP_MIB_MPCAPABLEPASSIVEACK, /* Received third ACK with MP_CAPABLE */
+ MPTCP_MIB_MPCAPABLEPASSIVEFALLBACK,/* Server-side fallback during 3-way handshake */
+ MPTCP_MIB_MPCAPABLEACTIVEFALLBACK, /* Client-side fallback during 3-way handshake */
++ MPTCP_MIB_MPCAPABLEENDPATTEMPT, /* Prohibited MPC to port-based endp */
+ MPTCP_MIB_TOKENFALLBACKINIT, /* Could not init/allocate token */
+ MPTCP_MIB_RETRANSSEGS, /* Segments retransmitted at the MPTCP-level */
+ MPTCP_MIB_JOINNOTOKEN, /* Received MP_JOIN but the token was not found */
+--- a/net/mptcp/pm_netlink.c
++++ b/net/mptcp/pm_netlink.c
+@@ -1125,6 +1125,7 @@ static int mptcp_pm_nl_create_listen_soc
+ */
+ inet_sk_state_store(newsk, TCP_LISTEN);
+ lock_sock(ssk);
++ WRITE_ONCE(mptcp_subflow_ctx(ssk)->pm_listener, true);
+ err = __inet_listen_sk(ssk, backlog);
+ if (!err)
+ mptcp_event_pm_listener(ssk, MPTCP_EVENT_LISTENER_CREATED);
+--- a/net/mptcp/protocol.h
++++ b/net/mptcp/protocol.h
+@@ -504,6 +504,7 @@ struct mptcp_subflow_context {
+ __unused : 9;
+ enum mptcp_data_avail data_avail;
+ bool scheduled;
++ bool pm_listener; /* a listener managed by the kernel PM? */
+ u32 remote_nonce;
+ u64 thmac;
+ u32 local_nonce;
+--- a/net/mptcp/subflow.c
++++ b/net/mptcp/subflow.c
+@@ -132,6 +132,13 @@ static void subflow_add_reset_reason(str
+ }
+ }
+
++static int subflow_reset_req_endp(struct request_sock *req, struct sk_buff *skb)
++{
++ SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_MPCAPABLEENDPATTEMPT);
++ subflow_add_reset_reason(skb, MPTCP_RST_EPROHIBIT);
++ return -EPERM;
++}
++
+ /* Init mptcp request socket.
+ *
+ * Returns an error code if a JOIN has failed and a TCP reset
+@@ -163,6 +170,8 @@ static int subflow_check_req(struct requ
+ if (opt_mp_capable) {
+ SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_MPCAPABLEPASSIVE);
+
++ if (unlikely(listener->pm_listener))
++ return subflow_reset_req_endp(req, skb);
+ if (opt_mp_join)
+ return 0;
+ } else if (opt_mp_join) {
+@@ -170,6 +179,8 @@ static int subflow_check_req(struct requ
+
+ if (mp_opt.backup)
+ SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_JOINSYNBACKUPRX);
++ } else if (unlikely(listener->pm_listener)) {
++ return subflow_reset_req_endp(req, skb);
+ }
+
+ if (opt_mp_capable && listener->request_mptcp) {
projects / thirdparty / kernel / stable-queue.git / commitdiff
