[v6.1] WARNING in mptcp_nl_cmd_set_flags

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 8e60a714ba3b Linux 6.1.132
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=13099404580000
kernel config: https://syzkaller.appspot.com/x/.config?x=ebc45e145d6155ea
dashboard link: https://syzkaller.appspot.com/bug?extid=d61a77d26f4c1e0f6ee7
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/c8b8da8486ff/disk-8e60a714.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/ad79748d8748/vmlinux-8e60a714.xz
kernel image: https://storage.googleapis.com/syzbot-assets/28699fcb5d47/bzImage-8e60a714.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+d61a77...@syzkaller.appspotmail.com

------------[ cut here ]------------
WARNING: CPU: 0 PID: 15333 at net/mptcp/pm_netlink.c:1548 __mark_subflow_endp_available include/linux/refcount.h:-1 [inline]
WARNING: CPU: 0 PID: 15333 at net/mptcp/pm_netlink.c:1548 mptcp_pm_nl_fullmesh net/mptcp/pm_netlink.c:2018 [inline]
WARNING: CPU: 0 PID: 15333 at net/mptcp/pm_netlink.c:1548 mptcp_nl_set_flags net/mptcp/pm_netlink.c:2041 [inline]
WARNING: CPU: 0 PID: 15333 at net/mptcp/pm_netlink.c:1548 mptcp_nl_cmd_set_flags+0xe58/0x11f0 net/mptcp/pm_netlink.c:2107
Modules linked in:
CPU: 0 PID: 15333 Comm: syz.4.2446 Not tainted 6.1.132-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
RIP: 0010:__mark_subflow_endp_available net/mptcp/pm_netlink.c:1548 [inline]
RIP: 0010:mptcp_pm_nl_fullmesh net/mptcp/pm_netlink.c:2018 [inline]
RIP: 0010:mptcp_nl_set_flags net/mptcp/pm_netlink.c:2041 [inline]
RIP: 0010:mptcp_nl_cmd_set_flags+0xe58/0x11f0 net/mptcp/pm_netlink.c:2107
Code: 0e 01 00 00 49 89 c5 e8 26 38 e7 f6 e9 c0 fc ff ff e8 1c 38 e7 f6 4c 89 f7 be 03 00 00 00 e8 df 78 a0 f9 eb a0 e8 08 38 e7 f6 <0f> 0b e9 10 ff ff ff 89 d9 80 e1 07 38 c1 0f 8c d3 fc ff ff 48 89
RSP: 0018:ffffc900034cf260 EFLAGS: 00010283
RAX: ffffffff8aa37248 RBX: 0000000000000000 RCX: 0000000000080000
RDX: ffffc9000ee4d000 RSI: 0000000000002f37 RDI: 0000000000002f38
RBP: ffffc900034cf510 R08: ffffffff8aa37140 R09: ffffed100f1a45a0
R10: 0000000000000000 R11: dffffc0000000001 R12: dffffc0000000000
R13: ffff888078d22280 R14: ffff888078d22cf0 R15: 1ffff1100f1a459e
FS: 00007f03262d16c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b2e10aff8 CR3: 000000001ce7a000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
genl_family_rcv_msg_doit net/netlink/genetlink.c:756 [inline]
genl_family_rcv_msg net/netlink/genetlink.c:833 [inline]
genl_rcv_msg+0xbfa/0xf50 net/netlink/genetlink.c:850
netlink_rcv_skb+0x1cd/0x410 net/netlink/af_netlink.c:2493
genl_rcv+0x24/0x40 net/netlink/genetlink.c:861
netlink_unicast_kernel net/netlink/af_netlink.c:1311 [inline]
netlink_unicast+0x7e2/0x970 net/netlink/af_netlink.c:1337
netlink_sendmsg+0xa26/0xd60 net/netlink/af_netlink.c:1859
sock_sendmsg_nosec net/socket.c:718 [inline]
__sock_sendmsg net/socket.c:730 [inline]
____sys_sendmsg+0x5d3/0x9a0 net/socket.c:2519
___sys_sendmsg net/socket.c:2573 [inline]
__sys_sendmsg+0x2a9/0x390 net/socket.c:2602
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f032538d169
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f03262d1038 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f03255a5fa0 RCX: 00007f032538d169
RDX: 0000000000000000 RSI: 0000200000000480 RDI: 0000000000000006
RBP: 00007f032540e2a0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f03255a5fa0 R15: 00007ffde1f50f68
</TASK>


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.