======================================================
WARNING: possible circular locking dependency detected
6.4.0-syzkaller #0 Not tainted
------------------------------------------------------
syz.0.7327/22857 is trying to acquire lock:
ffffffff85a38ed8 (nr_neigh_list_lock){+...}-{3:3}, at: spin_lock_bh include/linux/spinlock.h:355 [inline]
ffffffff85a38ed8 (nr_neigh_list_lock){+...}-{3:3}, at: nr_remove_neigh+0x1c/0x180 net/netrom/nr_route.c:315

but task is already holding lock:
ffff88816c12dc70 (&nr_node->node_lock){+...}-{3:3}, at: spin_lock_bh include/linux/spinlock.h:355 [inline]
ffff88816c12dc70 (&nr_node->node_lock){+...}-{3:3}, at: nr_node_lock include/net/netrom.h:152 [inline]
ffff88816c12dc70 (&nr_node->node_lock){+...}-{3:3}, at: nr_add_node+0x36c/0x15a0 net/netrom/nr_route.c:214

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (&nr_node->node_lock){+...}-{3:3}:
       __raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline]
       _raw_spin_lock_bh+0x33/0x40 kernel/locking/spinlock.c:178
       spin_lock_bh include/linux/spinlock.h:355 [inline]
       nr_node_lock include/net/netrom.h:152 [inline]
       nr_rt_device_down+0x125/0x4f0 net/netrom/nr_route.c:524
       nr_device_event+0xa9/0xd0 net/netrom/af_netrom.c:126
       notifier_call_chain+0x4b/0x1d0 kernel/notifier.c:93
       call_netdevice_notifiers_info net/core/dev.c:1935 [inline]
       call_netdevice_notifiers_info net/core/dev.c:1920 [inline]
       call_netdevice_notifiers_extack net/core/dev.c:1973 [inline]
       call_netdevice_notifiers net/core/dev.c:1987 [inline]
       __dev_notify_flags+0x1a4/0x290 net/core/dev.c:8609
       dev_change_flags+0x71/0x90 net/core/dev.c:8645
       dev_ifsioc+0x3c6/0x770 net/core/dev_ioctl.c:348
       dev_ioctl+0x1a7/0x7c0 net/core/dev_ioctl.c:605
       sock_do_ioctl+0x10c/0x1a0 net/socket.c:1216
       sock_ioctl+0x156/0x4a0 net/socket.c:1319
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:870 [inline]
       __se_sys_ioctl fs/ioctl.c:856 [inline]
       __x64_sys_ioctl+0xf6/0x150 fs/ioctl.c:856
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x3c/0xc0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x6f/0xd9

-> #1 (nr_node_list_lock){+...}-{3:3}:
       __raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline]
       _raw_spin_lock_bh+0x33/0x40 kernel/locking/spinlock.c:178
       spin_lock_bh include/linux/spinlock.h:355 [inline]
       nr_rt_device_down+0x87/0x4f0 net/netrom/nr_route.c:522
       nr_device_event+0xa9/0xd0 net/netrom/af_netrom.c:126
       notifier_call_chain+0x4b/0x1d0 kernel/notifier.c:93
       call_netdevice_notifiers_info net/core/dev.c:1935 [inline]
       call_netdevice_notifiers_info net/core/dev.c:1920 [inline]
       call_netdevice_notifiers_extack net/core/dev.c:1973 [inline]
       call_netdevice_notifiers net/core/dev.c:1987 [inline]
       __dev_notify_flags+0x1a4/0x290 net/core/dev.c:8609
       dev_change_flags+0x71/0x90 net/core/dev.c:8645
       dev_ifsioc+0x3c6/0x770 net/core/dev_ioctl.c:348
       dev_ioctl+0x1a7/0x7c0 net/core/dev_ioctl.c:605
       sock_do_ioctl+0x10c/0x1a0 net/socket.c:1216
       sock_ioctl+0x156/0x4a0 net/socket.c:1319
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:870 [inline]
       __se_sys_ioctl fs/ioctl.c:856 [inline]
       __x64_sys_ioctl+0xf6/0x150 fs/ioctl.c:856
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x3c/0xc0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x6f/0xd9

-> #0 (nr_neigh_list_lock){+...}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3113 [inline]
       check_prevs_add kernel/locking/lockdep.c:3232 [inline]
       validate_chain kernel/locking/lockdep.c:3847 [inline]
       __lock_acquire+0x13fe/0x1be0 kernel/locking/lockdep.c:5088
       lock_acquire kernel/locking/lockdep.c:5705 [inline]
       lock_acquire+0xcd/0x2d0 kernel/locking/lockdep.c:5670
       __raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline]
       _raw_spin_lock_bh+0x33/0x40 kernel/locking/spinlock.c:178
       spin_lock_bh include/linux/spinlock.h:355 [inline]
       nr_remove_neigh+0x1c/0x180 net/netrom/nr_route.c:315
       nr_add_node+0x1396/0x15a0 net/netrom/nr_route.c:249
       nr_rt_ioctl+0xd0b/0x1a00 net/netrom/nr_route.c:656
       nr_ioctl+0x130/0x1d0 net/netrom/af_netrom.c:1249
       sock_do_ioctl+0x82/0x1a0 net/socket.c:1202
       sock_ioctl+0x156/0x4a0 net/socket.c:1319
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:870 [inline]
       __se_sys_ioctl fs/ioctl.c:856 [inline]
       __x64_sys_ioctl+0xf6/0x150 fs/ioctl.c:856
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x3c/0xc0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x6f/0xd9

other info that might help us debug this:

Chain exists of:
  nr_neigh_list_lock --> nr_node_list_lock --> &nr_node->node_lock

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&nr_node->node_lock);
                               lock(nr_node_list_lock);
                               lock(&nr_node->node_lock);
  lock(nr_neigh_list_lock);

 *** DEADLOCK ***

1 lock held by syz.0.7327/22857:
 #0: ffff88816c12dc70 (&nr_node->node_lock){+...}-{3:3}, at: spin_lock_bh include/linux/spinlock.h:355 [inline]
 #0: ffff88816c12dc70 (&nr_node->node_lock){+...}-{3:3}, at: nr_node_lock include/net/netrom.h:152 [inline]
 #0: ffff88816c12dc70 (&nr_node->node_lock){+...}-{3:3}, at: nr_add_node+0x36c/0x15a0 net/netrom/nr_route.c:214

stack backtrace:
CPU: 1 PID: 22857 Comm: syz.0.7327 Not tainted 6.4.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 12/27/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0xd9/0x1b0 lib/dump_stack.c:106
 check_noncircular+0xf8/0x110 kernel/locking/lockdep.c:2188
 check_prev_add kernel/locking/lockdep.c:3113 [inline]
 check_prevs_add kernel/locking/lockdep.c:3232 [inline]
 validate_chain kernel/locking/lockdep.c:3847 [inline]
 __lock_acquire+0x13fe/0x1be0 kernel/locking/lockdep.c:5088
 lock_acquire kernel/locking/lockdep.c:5705 [inline]
 lock_acquire+0xcd/0x2d0 kernel/locking/lockdep.c:5670
 __raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline]
 _raw_spin_lock_bh+0x33/0x40 kernel/locking/spinlock.c:178
 spin_lock_bh include/linux/spinlock.h:355 [inline]
 nr_remove_neigh+0x1c/0x180 net/netrom/nr_route.c:315
 nr_add_node+0x1396/0x15a0 net/netrom/nr_route.c:249
 nr_rt_ioctl+0xd0b/0x1a00 net/netrom/nr_route.c:656
 nr_ioctl+0x130/0x1d0 net/netrom/af_netrom.c:1249
 sock_do_ioctl+0x82/0x1a0 net/socket.c:1202
 sock_ioctl+0x156/0x4a0 net/socket.c:1319
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:870 [inline]
 __se_sys_ioctl fs/ioctl.c:856 [inline]
 __x64_sys_ioctl+0xf6/0x150 fs/ioctl.c:856
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3c/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x6f/0xd9
RIP: 0033:0x7f025598cde9
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:00007f0256766038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f0255ba6160 RCX: 00007f025598cde9
RDX: 0000200000000280 RSI: 000000000000890b RDI: 0000000000000008
RBP: 00007f0255a0e2a0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f0255ba6160 R15: 00007fff6d8f1ea8
 </TASK>