[PATCH 6.1 43/64] mptcp: ensure context reset on disconnect()

Greg Kroah-Hartman
2026-02-17T20:47:20Z

From: Paolo Abeni <pabeni@redhat.com>

commit 86730ac255b0497a272704de9a1df559f5d6602e upstream.

After the blamed commit below, if the MPC subflow is already in TCP_CLOSE
status or has fallback to TCP at mptcp_disconnect() time,
mptcp_do_fastclose() skips setting the `send_fastclose flag` and the later
__mptcp_close_ssk() does not reset anymore the related subflow context.

Any later connection will be created with both the `request_mptcp` flag
and the msk-level fallback status off (it is unconditionally cleared at
MPTCP disconnect time), leading to a warning in subflow_data_ready():

WARNING: CPU: 26 PID: 8996 at net/mptcp/subflow.c:1519 subflow_data_ready (net/mptcp/subflow.c:1519 (discriminator 13))
Modules linked in:
CPU: 26 UID: 0 PID: 8996 Comm: syz.22.39 Not tainted 6.18.0-rc7-05427-g11fc074f6c36 #1 PREEMPT(voluntary)
Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
RIP: 0010:subflow_data_ready (net/mptcp/subflow.c:1519 (discriminator 13))
Code: 90 0f 0b 90 90 e9 04 fe ff ff e8 b7 1e f5 fe 89 ee bf 07 00 00 00 e8 db 19 f5 fe 83 fd 07 0f 84 35 ff ff ff e8 9d 1e f5 fe 90 <0f> 0b 90 e9 27 ff ff ff e8 8f 1e f5 fe 4c 89 e7 48 89 de e8 14 09
RSP: 0018:ffffc9002646fb30 EFLAGS: 00010293
RAX: 0000000000000000 RBX: ffff88813b218000 RCX: ffffffff825c8435
RDX: ffff8881300b3580 RSI: ffffffff825c8443 RDI: 0000000000000005
RBP: 000000000000000b R08: ffffffff825c8435 R09: 000000000000000b
R10: 0000000000000005 R11: 0000000000000007 R12: ffff888131ac0000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
FS: 00007f88330af6c0(0000) GS:ffff888a93dd2000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f88330aefe8 CR3: 000000010ff59000 CR4: 0000000000350ef0
Call Trace:
<TASK>
tcp_data_ready (net/ipv4/tcp_input.c:5356)
tcp_data_queue (net/ipv4/tcp_input.c:5445)
tcp_rcv_state_process (net/ipv4/tcp_input.c:7165)
tcp_v4_do_rcv (net/ipv4/tcp_ipv4.c:1955)
__release_sock (include/net/sock.h:1158 (discriminator 6) net/core/sock.c:3180 (discriminator 6))
release_sock (net/core/sock.c:3737)
mptcp_sendmsg (net/mptcp/protocol.c:1763 net/mptcp/protocol.c:1857)
inet_sendmsg (net/ipv4/af_inet.c:853 (discriminator 7))
__sys_sendto (net/socket.c:727 (discriminator 15) net/socket.c:742 (discriminator 15) net/socket.c:2244 (discriminator 15))
__x64_sys_sendto (net/socket.c:2247)
do_syscall_64 (arch/x86/entry/syscall_64.c:63 (discriminator 1) arch/x86/entry/syscall_64.c:94 (discriminator 1))
entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130)
RIP: 0033:0x7f883326702d

Address the issue setting an explicit `fastclosing` flag at fastclose
time, and checking such flag after mptcp_do_fastclose().

Fixes: ae155060247b ("mptcp: fix duplicate reset on fastclose")
Cc: stable@vger.kernel.org
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-v1-2-d1f9fd1c36c8@kernel.org
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
[ Conflicts in protocol.[ch] because the context has changed. ]
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/mptcp/protocol.c | 9 ++++++---
net/mptcp/protocol.h | 3 ++-
2 files changed, 8 insertions(+), 4 deletions(-)

--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -2456,10 +2456,10 @@ bool __mptcp_retransmit_pending_data(str
*/
static void __mptcp_subflow_disconnect(struct sock *ssk,
struct mptcp_subflow_context *subflow,
- unsigned int flags)
+ bool fastclosing)
{
if (((1 << ssk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN)) ||
- subflow->send_fastclose) {
+ fastclosing) {
/* The MPTCP code never wait on the subflow sockets, TCP-level
* disconnect should never fail
*/
@@ -2511,7 +2511,7 @@ static void __mptcp_close_ssk(struct soc

need_push = (flags & MPTCP_CF_PUSH) && __mptcp_retransmit_pending_data(sk);
if (!dispose_it) {
- __mptcp_subflow_disconnect(ssk, subflow, flags);
+ __mptcp_subflow_disconnect(ssk, subflow, msk->fastclosing);
if (msk->subflow && ssk == msk->subflow->sk)
msk->subflow->state = SS_UNCONNECTED;
release_sock(ssk);
@@ -2802,6 +2802,8 @@ static void mptcp_do_fastclose(struct so
struct mptcp_subflow_context *subflow, *tmp;
struct mptcp_sock *msk = mptcp_sk(sk);

+ msk->fastclosing = 1;
+
/* Explicitly send the fastclose reset as need */
if (__mptcp_check_fallback(msk))
return;
@@ -3290,6 +3292,7 @@ static int mptcp_disconnect(struct sock
WRITE_ONCE(msk->csum_enabled, mptcp_is_checksum_enabled(sock_net(sk)));
mptcp_pm_data_reset(msk);
mptcp_ca_reset(sk);
+ msk->fastclosing = 0;

WRITE_ONCE(sk->sk_shutdown, 0);
sk_error_report(sk);
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -289,7 +289,8 @@ struct mptcp_sock {
nodelay:1,
fastopening:1,
in_accept_queue:1,
- free_first:1;
+ free_first:1,
+ fastclosing:1;
int keepalive_cnt;
int keepalive_idle;
int keepalive_intvl;