syzbot

     __do_sys_sendto net/socket.c:2187 [inline]
     __se_sys_sendto net/socket.c:2183 [inline]
     __x64_sys_sendto+0xde/0x100 net/socket.c:2183
     do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
     do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
     entry_SYSCALL_64_after_hwframe+0x77/0x7f
------------[ cut here ]------------
WARNING: CPU: 0 PID: 12 at lib/ref_tracker.c:179 ref_tracker_dir_exit+0x3d0/0x510 lib/ref_tracker.c:179
Modules linked in:
CPU: 0 UID: 0 PID: 12 Comm: kworker/u8:0 Not tainted 6.15.0-syzkaller-10820-gcd2e103d57e5 #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Workqueue: netns cleanup_net
RIP: 0010:ref_tracker_dir_exit+0x3d0/0x510 lib/ref_tracker.c:179
Code: 26 cb fc 48 89 df 48 8b 74 24 10 e8 ba f7 71 06 eb 1b e8 f3 25 cb fc 48 8b 5c 24 18 48 89 df 48 8b 74 24 10 e8 a1 f7 71 06 90 <0f> 0b 90 4c 8d 73 44 4c 89 f7 be 04 00 00 00 e8 fc b1 2e fd 4c 89
RSP: 0018:ffffc900001175d8 EFLAGS: 00010246
RAX: 03cda7b46790a600 RBX: ffff888071064610 RCX: 0000000000000000
RDX: 0000000000000007 RSI: ffffffff8d9705da RDI: 00000000ffffffff
RBP: ffff888071064660 R08: ffffffff8fa0bcf7 R09: 1ffffffff1f4179e
R10: dffffc0000000000 R11: fffffbfff1f4179f R12: ffff88804dc71e40
R13: ffff888071064660 R14: dffffc0000000000 R15: 1ffff11009b8e3c8
FS:  0000000000000000(0000) GS:ffff888125c5f000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f2a33e1ff98 CR3: 0000000074f6c000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000097 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 free_netdev+0x46a/0x700 net/core/dev.c:11874
 netdev_run_todo+0xd0c/0xea0 net/core/dev.c:11406
 default_device_exit_batch+0x81e/0x890 net/core/dev.c:12644
 ops_exit_list net/core/net_namespace.c:206 [inline]
 ops_undo_list+0x522/0x990 net/core/net_namespace.c:253
 cleanup_net+0x4c5/0x800 net/core/net_namespace.c:686
 process_one_work kernel/workqueue.c:3238 [inline]
 process_scheduled_works+0xade/0x17b0 kernel/workqueue.c:3321
 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3402
 kthread+0x711/0x8a0 kernel/kthread.c:464
 ret_from_fork+0x3fc/0x770 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>