netdev - [syzbot] [mptcp?] WARNING in subflow_data

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Message-ID: <68a5c278.050a0220.3d78fd.0000.GAE@google.com>
Date: Wed, 20 Aug 2025 05:41:28 -0700
From: syzbot <syzbot+0ff6b771b4f7a5bce83b@...kaller.appspotmail.com>
To: davem@...emloft.net, edumazet@...gle.com, geliang@...nel.org, 
	horms@...nel.org, kuba@...nel.org, linux-kernel@...r.kernel.org, 
	martineau@...nel.org, matttbe@...nel.org, mptcp@...ts.linux.dev, 
	netdev@...r.kernel.org, pabeni@...hat.com, syzkaller-bugs@...glegroups.com
Subject: [syzbot] [mptcp?] WARNING in subflow_data_ready (4)

Hello,

syzbot found the following issue on:

HEAD commit:    b19a97d57c15 Merge tag 'pull-fixes' of git://git.kernel.or..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=174817a2580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=b7511150b112b9c3
dashboard link: https://syzkaller.appspot.com/bug?extid=0ff6b771b4f7a5bce83b
compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-b19a97d5.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/d6e98c49ae62/vmlinux-b19a97d5.xz
kernel image: https://storage.googleapis.com/syzbot-assets/c90ded1d8e17/bzImage-b19a97d5.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+0ff6b771b4f7a5bce83b@...kaller.appspotmail.com

------------[ cut here ]------------
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>


---
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