======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.1.5584/28052 is trying to acquire lock:
ffffffff8ff4be18 (nr_neigh_list_lock){+...}-{3:3}, at: spin_lock_bh include/linux/spinlock.h:348 [inline]
ffffffff8ff4be18 (nr_neigh_list_lock){+...}-{3:3}, at: nr_remove_neigh net/netrom/nr_route.c:307 [inline]
ffffffff8ff4be18 (nr_neigh_list_lock){+...}-{3:3}, at: nr_del_node+0x57d/0xbb0 net/netrom/nr_route.c:342

but task is already holding lock:
ffff88801b754270 (&nr_node->node_lock){+...}-{3:3}, at: spin_lock_bh include/linux/spinlock.h:348 [inline]
ffff88801b754270 (&nr_node->node_lock){+...}-{3:3}, at: nr_node_lock include/net/netrom.h:152 [inline]
ffff88801b754270 (&nr_node->node_lock){+...}-{3:3}, at: nr_del_node+0x2a9/0xbb0 net/netrom/nr_route.c:335

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:150 [inline]
       _raw_spin_lock_bh+0x36/0x50 kernel/locking/spinlock.c:182
       spin_lock_bh include/linux/spinlock.h:348 [inline]
       nr_node_lock include/net/netrom.h:152 [inline]
       nr_rt_device_down+0x153/0x860 net/netrom/nr_route.c:519
       nr_device_event+0x137/0x150 net/netrom/af_netrom.c:126
       notifier_call_chain+0x1ad/0x3d0 kernel/notifier.c:85
       call_netdevice_notifiers_extack net/core/dev.c:2287 [inline]
       call_netdevice_notifiers net/core/dev.c:2301 [inline]
       __dev_notify_flags+0x16d/0x310 net/core/dev.c:9851
       netif_change_flags+0xe8/0x1a0 net/core/dev.c:9878
       dev_change_flags+0x130/0x260 net/core/dev_api.c:68
       dev_ioctl+0x7b4/0x1150 net/core/dev_ioctl.c:814
       sock_do_ioctl+0x23e/0x320 net/socket.c:1327
       sock_ioctl+0x5c6/0x7f0 net/socket.c:1434
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:597 [inline]
       __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (nr_node_list_lock){+...}-{3:3}:
       __raw_spin_lock_bh include/linux/spinlock_api_smp.h:150 [inline]
       _raw_spin_lock_bh+0x36/0x50 kernel/locking/spinlock.c:182
       spin_lock_bh include/linux/spinlock.h:348 [inline]
       nr_rt_device_down+0xbe/0x860 net/netrom/nr_route.c:517
       nr_device_event+0x137/0x150 net/netrom/af_netrom.c:126
       notifier_call_chain+0x1ad/0x3d0 kernel/notifier.c:85
       call_netdevice_notifiers_extack net/core/dev.c:2287 [inline]
       call_netdevice_notifiers net/core/dev.c:2301 [inline]
       __dev_notify_flags+0x16d/0x310 net/core/dev.c:9851
       netif_change_flags+0xe8/0x1a0 net/core/dev.c:9878
       dev_change_flags+0x130/0x260 net/core/dev_api.c:68
       dev_ioctl+0x7b4/0x1150 net/core/dev_ioctl.c:814
       sock_do_ioctl+0x23e/0x320 net/socket.c:1327
       sock_ioctl+0x5c6/0x7f0 net/socket.c:1434
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:597 [inline]
       __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (nr_neigh_list_lock){+...}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3165 [inline]
       check_prevs_add kernel/locking/lockdep.c:3284 [inline]
       validate_chain kernel/locking/lockdep.c:3908 [inline]
       __lock_acquire+0x15a5/0x2cf0 kernel/locking/lockdep.c:5237
       lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5868
       __raw_spin_lock_bh include/linux/spinlock_api_smp.h:150 [inline]
       _raw_spin_lock_bh+0x36/0x50 kernel/locking/spinlock.c:182
       spin_lock_bh include/linux/spinlock.h:348 [inline]
       nr_remove_neigh net/netrom/nr_route.c:307 [inline]
       nr_del_node+0x57d/0xbb0 net/netrom/nr_route.c:342
       nr_rt_ioctl+0xb34/0xf90 net/netrom/nr_route.c:678
       sock_do_ioctl+0x101/0x320 net/socket.c:1313
       sock_ioctl+0x5c6/0x7f0 net/socket.c:1434
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:597 [inline]
       __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x15f/0xf80 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:
  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 ***

2 locks held by syz.1.5584/28052:
 #0: ffffffff8ff4be78 (nr_node_list_lock){+...}-{3:3}, at: spin_lock_bh include/linux/spinlock.h:348 [inline]
 #0: ffffffff8ff4be78 (nr_node_list_lock){+...}-{3:3}, at: nr_del_node+0x253/0xbb0 net/netrom/nr_route.c:334
 #1: ffff88801b754270 (&nr_node->node_lock){+...}-{3:3}, at: spin_lock_bh include/linux/spinlock.h:348 [inline]
 #1: ffff88801b754270 (&nr_node->node_lock){+...}-{3:3}, at: nr_node_lock include/net/netrom.h:152 [inline]
 #1: ffff88801b754270 (&nr_node->node_lock){+...}-{3:3}, at: nr_del_node+0x2a9/0xbb0 net/netrom/nr_route.c:335

stack backtrace:
CPU: 0 UID: 0 PID: 28052 Comm: syz.1.5584 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_circular_bug+0x2e1/0x300 kernel/locking/lockdep.c:2043
 check_noncircular+0x12e/0x150 kernel/locking/lockdep.c:2175
 check_prev_add kernel/locking/lockdep.c:3165 [inline]
 check_prevs_add kernel/locking/lockdep.c:3284 [inline]
 validate_chain kernel/locking/lockdep.c:3908 [inline]
 __lock_acquire+0x15a5/0x2cf0 kernel/locking/lockdep.c:5237
 lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5868
 __raw_spin_lock_bh include/linux/spinlock_api_smp.h:150 [inline]
 _raw_spin_lock_bh+0x36/0x50 kernel/locking/spinlock.c:182
 spin_lock_bh include/linux/spinlock.h:348 [inline]
 nr_remove_neigh net/netrom/nr_route.c:307 [inline]
 nr_del_node+0x57d/0xbb0 net/netrom/nr_route.c:342
 nr_rt_ioctl+0xb34/0xf90 net/netrom/nr_route.c:678
 sock_do_ioctl+0x101/0x320 net/socket.c:1313
 sock_ioctl+0x5c6/0x7f0 net/socket.c:1434
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:597 [inline]
 __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f4cf799c819
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f4cf87cb028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f4cf7c15fa0 RCX: 00007f4cf799c819
RDX: 00002000000001c0 RSI: 000000000000890c RDI: 0000000000000006
RBP: 00007f4cf7a32c91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f4cf7c16038 R14: 00007f4cf7c15fa0 R15: 00007ffe06429c98
 </TASK>
netlink: 24 bytes leftover after parsing attributes in process `syz.1.5584'.
tipc: Enabling of bearer <eth:syzkaller0> rejected, failed to enable media
sctp: [Deprecated]: syz.1.5584 (pid 28052) Use of int in max_burst socket option deprecated.
Use struct sctp_assoc_value instead