[ Upstream commit
71154bbe49423128c1c8577b6576de1ed6836830 ]
Syzkaller reports a simult-connect race leading to inconsistent fallback
status:
WARNING: CPU: 3 PID: 33 at net/mptcp/subflow.c:1515 subflow_data_ready+0x40b/0x7c0 net/mptcp/subflow.c:1515
Modules linked in:
CPU: 3 UID: 0 PID: 33 Comm: ksoftirqd/3 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
RIP: 0010:subflow_data_ready+0x40b/0x7c0 net/mptcp/subflow.c:1515
Code: 89 ee e8 78 61 3c f6 40 84 ed 75 21 e8 8e 66 3c f6 44 89 fe bf 07 00 00 00 e8 c1 61 3c f6 41 83 ff 07 74 09 e8 76 66 3c f6 90 <0f> 0b 90 e8 6d 66 3c f6 48 89 df e8 e5 ad ff ff 31 ff 89 c5 89 c6
RSP: 0018:
ffffc900006cf338 EFLAGS:
00010246
RAX:
0000000000000000 RBX:
ffff888031acd100 RCX:
ffffffff8b7f2abf
RDX:
ffff88801e6ea440 RSI:
ffffffff8b7f2aca RDI:
0000000000000005
RBP:
0000000000000000 R08:
0000000000000005 R09:
0000000000000007
R10:
0000000000000004 R11:
0000000000002c10 R12:
ffff88802ba69900
R13:
1ffff920000d9e67 R14:
ffff888046f81800 R15:
0000000000000004
FS:
0000000000000000(0000) GS:
ffff8880d69bc000(0000) knlGS:
0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0:
0000000080050033
CR2:
0000560fc0ca1670 CR3:
0000000032c3a000 CR4:
0000000000352ef0
Call Trace:
<TASK>
tcp_data_queue+0x13b0/0x4f90 net/ipv4/tcp_input.c:5197
tcp_rcv_state_process+0xfdf/0x4ec0 net/ipv4/tcp_input.c:6922
tcp_v6_do_rcv+0x492/0x1740 net/ipv6/tcp_ipv6.c:1672
tcp_v6_rcv+0x2976/0x41e0 net/ipv6/tcp_ipv6.c:1918
ip6_protocol_deliver_rcu+0x188/0x1520 net/ipv6/ip6_input.c:438
ip6_input_finish+0x1e4/0x4b0 net/ipv6/ip6_input.c:489
NF_HOOK include/linux/netfilter.h:318 [inline]
NF_HOOK include/linux/netfilter.h:312 [inline]
ip6_input+0x105/0x2f0 net/ipv6/ip6_input.c:500
dst_input include/net/dst.h:471 [inline]
ip6_rcv_finish net/ipv6/ip6_input.c:79 [inline]
NF_HOOK include/linux/netfilter.h:318 [inline]
NF_HOOK include/linux/netfilter.h:312 [inline]
ipv6_rcv+0x264/0x650 net/ipv6/ip6_input.c:311
__netif_receive_skb_one_core+0x12d/0x1e0 net/core/dev.c:5979
__netif_receive_skb+0x1d/0x160 net/core/dev.c:6092
process_backlog+0x442/0x15e0 net/core/dev.c:6444
__napi_poll.constprop.0+0xba/0x550 net/core/dev.c:7494
napi_poll net/core/dev.c:7557 [inline]
net_rx_action+0xa9f/0xfe0 net/core/dev.c:7684
handle_softirqs+0x216/0x8e0 kernel/softirq.c:579
run_ksoftirqd kernel/softirq.c:968 [inline]
run_ksoftirqd+0x3a/0x60 kernel/softirq.c:960
smpboot_thread_fn+0x3f7/0xae0 kernel/smpboot.c:160
kthread+0x3c2/0x780 kernel/kthread.c:463
ret_from_fork+0x5d7/0x6f0 arch/x86/kernel/process.c:148
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>
The TCP subflow can process the simult-connect syn-ack packet after
transitioning to TCP_FIN1 state, bypassing the MPTCP fallback check,
as the sk_state_change() callback is not invoked for * -> FIN_WAIT1
transitions.
That will move the msk socket to an inconsistent status and the next
incoming data will hit the reported splat.
Close the race moving the simult-fallback check at the earliest possible
stage - that is at syn-ack generation time.
About the fixes tags: [2] was supposed to also fix this issue introduced
by [3]. [1] is required as a dependence: it was not explicitly marked as
a fix, but it is one and it has already been backported before [3]. In
other words, this commit should be backported up to [3], including [2]
and [1] if that's not already there.
Fixes: 23e89e8ee7be ("tcp: Don't drop SYN+ACK for simultaneous connect().") [1]
Fixes: 4fd19a307016 ("mptcp: fix inconsistent state on fastopen race") [2]
Fixes: 1e777f39b4d7 ("mptcp: add MSG_FASTOPEN sendmsg flag support") [3]
Cc: stable@vger.kernel.org
Reported-by: syzbot+0ff6b771b4f7a5bce83b@syzkaller.appspotmail.com
Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/586
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://patch.msgid.link/20251212-net-mptcp-subflow_data_ready-warn-v1-1-d1f9fd1c36c8@kernel.org
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
[ adapted mptcp_try_fallback() call ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
*/
subflow->snd_isn = TCP_SKB_CB(skb)->end_seq;
if (subflow->request_mptcp) {
+ if (unlikely(subflow_simultaneous_connect(sk))) {
+ WARN_ON_ONCE(!mptcp_try_fallback(sk));
+
+ /* Ensure mptcp_finish_connect() will not process the
+ * MPC handshake.
+ */
+ subflow->request_mptcp = 0;
+ return false;
+ }
+
opts->suboptions = OPTION_MPTCP_MPC_SYN;
opts->csum_reqd = mptcp_is_checksum_enabled(sock_net(sk));
opts->allow_join_id0 = mptcp_allow_join_id0(sock_net(sk));
{
struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
- return (1 << sk->sk_state) &
- (TCPF_ESTABLISHED | TCPF_FIN_WAIT1 | TCPF_FIN_WAIT2 | TCPF_CLOSING) &&
- is_active_ssk(subflow) &&
- !subflow->conn_finished;
+ /* Note that the sk state implies !subflow->conn_finished. */
+ return sk->sk_state == TCP_SYN_RECV && is_active_ssk(subflow);
}
#ifdef CONFIG_SYN_COOKIES
{
struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
struct sock *parent = subflow->conn;
- struct mptcp_sock *msk;
+ struct mptcp_sock *msk = mptcp_sk(parent);
__subflow_state_change(sk);
- msk = mptcp_sk(parent);
- if (subflow_simultaneous_connect(sk)) {
- WARN_ON_ONCE(!mptcp_try_fallback(sk));
- pr_fallback(msk);
- subflow->conn_finished = 1;
- mptcp_propagate_state(parent, sk, subflow, NULL);
- }
-
/* as recvmsg() does not acquire the subflow socket for ssk selection
* a fin packet carrying a DSS can be unnoticed if we don't trigger
* the data available machinery here.
projects / thirdparty / kernel / stable.git / commitdiff
