syzbot

======================================================
WARNING: possible circular locking dependency detected
6.15.0-syzkaller-13526-g7a912d04415b #0 Not tainted
------------------------------------------------------
syz.9.1954/12576 is trying to acquire lock:
ffff888035d60d30 (&dev_instance_lock_key#20){+.+.}-{4:4}, at: netdev_lock include/linux/netdevice.h:2756 [inline]
ffff888035d60d30 (&dev_instance_lock_key#20){+.+.}-{4:4}, at: netdev_lock_ops include/net/netdev_lock.h:42 [inline]
ffff888035d60d30 (&dev_instance_lock_key#20){+.+.}-{4:4}, at: xsk_bind+0x37c/0x1570 net/xdp/xsk.c:1189

but task is already holding lock:
ffff88802a25d6b0 (&xs->mutex){+.+.}-{4:4}, at: xsk_bind+0x1f1/0x1570 net/xdp/xsk.c:1177

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (&xs->mutex){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/mutex.c:602 [inline]
       __mutex_lock+0x199/0xb90 kernel/locking/mutex.c:747
       xsk_notifier+0x101/0x280 net/xdp/xsk.c:1649
       notifier_call_chain+0xbc/0x410 kernel/notifier.c:85
       call_netdevice_notifiers_info+0xbe/0x140 net/core/dev.c:2230
       call_netdevice_notifiers_extack net/core/dev.c:2268 [inline]
       call_netdevice_notifiers net/core/dev.c:2282 [inline]
       unregister_netdevice_many_notify+0xf9d/0x2700 net/core/dev.c:12077
       rtnl_delete_link net/core/rtnetlink.c:3511 [inline]
       rtnl_dellink+0x3cb/0xa80 net/core/rtnetlink.c:3553
       rtnetlink_rcv_msg+0x95e/0xe90 net/core/rtnetlink.c:6944
       netlink_rcv_skb+0x158/0x420 net/netlink/af_netlink.c:2534
       netlink_unicast_kernel net/netlink/af_netlink.c:1313 [inline]
       netlink_unicast+0x53d/0x7f0 net/netlink/af_netlink.c:1339
       netlink_sendmsg+0x8d1/0xdd0 net/netlink/af_netlink.c:1883
       sock_sendmsg_nosec net/socket.c:712 [inline]
       __sock_sendmsg net/socket.c:727 [inline]
       ____sys_sendmsg+0xa98/0xc70 net/socket.c:2566
       ___sys_sendmsg+0x134/0x1d0 net/socket.c:2620
       __sys_sendmsg+0x16d/0x220 net/socket.c:2652
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (&net->xdp.lock){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/mutex.c:602 [inline]
       __mutex_lock+0x199/0xb90 kernel/locking/mutex.c:747
       xsk_notifier+0xa4/0x280 net/xdp/xsk.c:1645
       notifier_call_chain+0xbc/0x410 kernel/notifier.c:85
       call_netdevice_notifiers_info+0xbe/0x140 net/core/dev.c:2230
       call_netdevice_notifiers_extack net/core/dev.c:2268 [inline]
       call_netdevice_notifiers net/core/dev.c:2282 [inline]
       unregister_netdevice_many_notify+0xf9d/0x2700 net/core/dev.c:12077
       unregister_netdevice_many net/core/dev.c:12140 [inline]
       unregister_netdevice_queue+0x305/0x3f0 net/core/dev.c:11984
       register_netdevice+0x18f1/0x2270 net/core/dev.c:11149
       lapbeth_new_device drivers/net/wan/lapbether.c:420 [inline]
       lapbeth_device_event+0x5b1/0xbe0 drivers/net/wan/lapbether.c:462
       notifier_call_chain+0xbc/0x410 kernel/notifier.c:85
       call_netdevice_notifiers_info+0xbe/0x140 net/core/dev.c:2230
       call_netdevice_notifiers_extack net/core/dev.c:2268 [inline]
       call_netdevice_notifiers net/core/dev.c:2282 [inline]
       __dev_notify_flags+0x12c/0x2e0 net/core/dev.c:9497
       netif_change_flags+0x108/0x160 net/core/dev.c:9526
       dev_change_flags+0xba/0x250 net/core/dev_api.c:68
       devinet_ioctl+0x11d5/0x1f50 net/ipv4/devinet.c:1200
       inet_ioctl+0x3a7/0x3f0 net/ipv4/af_inet.c:1001
       sock_do_ioctl+0x118/0x280 net/socket.c:1190
       sock_ioctl+0x227/0x6b0 net/socket.c:1311
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:907 [inline]
       __se_sys_ioctl fs/ioctl.c:893 [inline]
       __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:893
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (&dev_instance_lock_key#20){+.+.}-{4:4}:
       check_prev_add kernel/locking/lockdep.c:3168 [inline]
       check_prevs_add kernel/locking/lockdep.c:3287 [inline]
       validate_chain kernel/locking/lockdep.c:3911 [inline]
       __lock_acquire+0x126f/0x1c90 kernel/locking/lockdep.c:5240
       lock_acquire kernel/locking/lockdep.c:5871 [inline]
       lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5828
       __mutex_lock_common kernel/locking/mutex.c:602 [inline]
       __mutex_lock+0x199/0xb90 kernel/locking/mutex.c:747
       netdev_lock include/linux/netdevice.h:2756 [inline]
       netdev_lock_ops include/net/netdev_lock.h:42 [inline]
       xsk_bind+0x37c/0x1570 net/xdp/xsk.c:1189
       __sys_bind_socket net/socket.c:1810 [inline]
       __sys_bind_socket net/socket.c:1802 [inline]
       __sys_bind+0x1a7/0x260 net/socket.c:1841
       __do_sys_bind net/socket.c:1846 [inline]
       __se_sys_bind net/socket.c:1844 [inline]
       __x64_sys_bind+0x72/0xb0 net/socket.c:1844
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

Chain exists of:
  &dev_instance_lock_key#20 --> &net->xdp.lock --> &xs->mutex

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&xs->mutex);
                               lock(&net->xdp.lock);
                               lock(&xs->mutex);
  lock(&dev_instance_lock_key#20);

 *** DEADLOCK ***

2 locks held by syz.9.1954/12576:
 #0: ffffffff9034f1a8 (rtnl_mutex){+.+.}-{4:4}, at: xsk_bind+0x1dc/0x1570 net/xdp/xsk.c:1176
 #1: ffff88802a25d6b0 (&xs->mutex){+.+.}-{4:4}, at: xsk_bind+0x1f1/0x1570 net/xdp/xsk.c:1177

stack backtrace:
CPU: 0 UID: 0 PID: 12576 Comm: syz.9.1954 Not tainted 6.15.0-syzkaller-13526-g7a912d04415b #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
 print_circular_bug+0x275/0x350 kernel/locking/lockdep.c:2046
 check_noncircular+0x14c/0x170 kernel/locking/lockdep.c:2178
 check_prev_add kernel/locking/lockdep.c:3168 [inline]
 check_prevs_add kernel/locking/lockdep.c:3287 [inline]
 validate_chain kernel/locking/lockdep.c:3911 [inline]
 __lock_acquire+0x126f/0x1c90 kernel/locking/lockdep.c:5240
 lock_acquire kernel/locking/lockdep.c:5871 [inline]
 lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5828
 __mutex_lock_common kernel/locking/mutex.c:602 [inline]
 __mutex_lock+0x199/0xb90 kernel/locking/mutex.c:747
 netdev_lock include/linux/netdevice.h:2756 [inline]
 netdev_lock_ops include/net/netdev_lock.h:42 [inline]
 xsk_bind+0x37c/0x1570 net/xdp/xsk.c:1189
 __sys_bind_socket net/socket.c:1810 [inline]
 __sys_bind_socket net/socket.c:1802 [inline]
 __sys_bind+0x1a7/0x260 net/socket.c:1841
 __do_sys_bind net/socket.c:1846 [inline]
 __se_sys_bind net/socket.c:1844 [inline]
 __x64_sys_bind+0x72/0xb0 net/socket.c:1844
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f889098e929
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:00007f88918b2038 EFLAGS: 00000246 ORIG_RAX: 0000000000000031
RAX: ffffffffffffffda RBX: 00007f8890bb5fa0 RCX: 00007f889098e929
RDX: 000000000000002a RSI: 00002000000001c0 RDI: 0000000000000004
RBP: 00007f8890a10b39 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f8890bb5fa0 R15: 00007ffeb1964dd8
 </TASK>