Re: [syzbot] [mptcp?] WARNING in subflow_data_ready (4)

syzbot
2025-11-27T08:03:02Z

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
WARNING in subflow_data_ready

MPTCP: fallaback under lock 0 req mpc 1 req mpj 0 state 16 parent state 7 send 0 received 0
------------[ cut here ]------------
WARNING: CPU: 1 PID: 23 at net/mptcp/subflow.c:1527 subflow_data_ready+0x59d/0x980 net/mptcp/subflow.c:1527
Modules linked in:
CPU: 1 UID: 0 PID: 23 Comm: ksoftirqd/1 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:subflow_data_ready+0x59d/0x980 net/mptcp/subflow.c:1527
Code: e0 48 c7 c7 c0 71 ee 8c 44 89 f9 8b 54 24 1c 48 c1 ee 02 45 0f b7 c0 83 e6 01 e8 2e 6c 51 f6 48 8b 7c 24 10 e8 44 ee 16 00 90 <0f> 0b 90 58 5a e8 e9 fb 72 f6 48 89 df e8 51 ac ff ff 31 ff 89 c5
RSP: 0018:ffffc900001d7348 EFLAGS: 00010202
RAX: 0000000000000101 RBX: ffff8880343cd940 RCX: 0000000000000002
RDX: 0000000000000000 RSI: ffffffff8da29344 RDI: ffffffff8bf078c0
RBP: ffff8880312b1538 R08: 0000000000000001 R09: 0000000000000001
R10: ffffffff90824bd7 R11: 0000000000000001 R12: ffff8880312b0c00
R13: 1ffff9200003ae70 R14: 0000000000000004 R15: 0000000000000000
FS: 0000000000000000(0000) GS:ffff888124b0d000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f6ced887d58 CR3: 0000000064f00000 CR4: 00000000003526f0
Call Trace:
<TASK>
tcp_data_ready+0x110/0x550 net/ipv4/tcp_input.c:5355
tcp_data_queue+0x1aa6/0x5000 net/ipv4/tcp_input.c:5445
tcp_rcv_state_process+0xfb6/0x6490 net/ipv4/tcp_input.c:7159
tcp_v4_do_rcv+0x68e/0x10a0 net/ipv4/tcp_ipv4.c:1954
tcp_v4_rcv+0x3077/0x4db0 net/ipv4/tcp_ipv4.c:2374
ip_protocol_deliver_rcu+0xba/0x4c0 net/ipv4/ip_input.c:205
ip_local_deliver_finish+0x3f2/0x720 net/ipv4/ip_input.c:239
NF_HOOK include/linux/netfilter.h:318 [inline]
NF_HOOK include/linux/netfilter.h:312 [inline]
ip_local_deliver+0x18e/0x1f0 net/ipv4/ip_input.c:260
dst_input include/net/dst.h:474 [inline]
ip_rcv_finish net/ipv4/ip_input.c:453 [inline]
NF_HOOK include/linux/netfilter.h:318 [inline]
NF_HOOK include/linux/netfilter.h:312 [inline]
ip_rcv+0x2e0/0x600 net/ipv4/ip_input.c:573
__netif_receive_skb_one_core+0x197/0x1e0 net/core/dev.c:6079
__netif_receive_skb+0x1d/0x160 net/core/dev.c:6192
process_backlog+0x439/0x15e0 net/core/dev.c:6544
__napi_poll.constprop.0+0xba/0x550 net/core/dev.c:7594
napi_poll net/core/dev.c:7657 [inline]
net_rx_action+0x97f/0xef0 net/core/dev.c:7784
handle_softirqs+0x219/0x8e0 kernel/softirq.c:622
run_ksoftirqd kernel/softirq.c:1063 [inline]
run_ksoftirqd+0x3a/0x60 kernel/softirq.c:1055
smpboot_thread_fn+0x3f7/0xae0 kernel/smpboot.c:160
kthread+0x3c5/0x780 kernel/kthread.c:463
ret_from_fork+0x675/0x7d0 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>

Tested on:

commit: 8e621c9a Merge tag 'net-6.18-rc7' of git://git.kernel...
git tree: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
console output: https://syzkaller.appspot.com/x/log.txt?x=14916f42580000
kernel config: https://syzkaller.appspot.com/x/.config?x=1cd7f786c0f5182f
dashboard link: https://syzkaller.appspot.com/bug?extid=0ff6b771b4f7a5bce83b
compiler: gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
patch: https://syzkaller.appspot.com/x/patch.diff?x=158f657c580000