======================================================
WARNING: possible circular locking dependency detected
6.13.0-syzkaller-02526-gc4b9570cfb63 #0 Not tainted
------------------------------------------------------
syz.3.1882/10770 is trying to acquire lock:
ffff0000c462a470 (&nr_node->node_lock){+...}-{3:3}, at: spin_lock_bh include/linux/spinlock.h:356 [inline]
ffff0000c462a470 (&nr_node->node_lock){+...}-{3:3}, at: nr_node_lock include/net/netrom.h:152 [inline]
ffff0000c462a470 (&nr_node->node_lock){+...}-{3:3}, at: nr_rt_device_down+0x138/0x6f8 net/netrom/nr_route.c:519

but task is already holding lock:
ffff80009024b158 (nr_node_list_lock){+...}-{3:3}, at: spin_lock_bh include/linux/spinlock.h:356 [inline]
ffff80009024b158 (nr_node_list_lock){+...}-{3:3}, at: nr_rt_device_down+0xb8/0x6f8 net/netrom/nr_route.c:517

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (nr_node_list_lock){+...}-{3:3}:
       __raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline]
       _raw_spin_lock_bh+0x48/0x60 kernel/locking/spinlock.c:178
       spin_lock_bh include/linux/spinlock.h:356 [inline]
       nr_rt_device_down+0xb8/0x6f8 net/netrom/nr_route.c:517
       nr_device_event+0x138/0x164 net/netrom/af_netrom.c:126
       notifier_call_chain+0x1c4/0x550 kernel/notifier.c:85
       raw_notifier_call_chain+0x3c/0x50 kernel/notifier.c:453
       __dev_notify_flags+0x2c4/0x550
       dev_change_flags+0xd0/0x15c net/core/dev.c:9045
       dev_ifsioc+0xc8/0x904 net/core/dev_ioctl.c:526
       dev_ioctl+0x4d8/0xd34 net/core/dev_ioctl.c:783
       sock_do_ioctl+0x1d4/0x2d0 net/socket.c:1223
       sock_ioctl+0x4ec/0x838 net/socket.c:1328
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:906 [inline]
       __se_sys_ioctl fs/ioctl.c:892 [inline]
       __arm64_sys_ioctl+0x14c/0x1cc fs/ioctl.c:892
       __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
       invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:49
       el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132
       do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151
       el0_svc+0x54/0x168 arch/arm64/kernel/entry-common.c:744
       el0t_64_sync_handler+0x84/0x108 arch/arm64/kernel/entry-common.c:762
       el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:600

-> #1 (nr_neigh_list_lock){+...}-{3:3}:
       __raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline]
       _raw_spin_lock_bh+0x48/0x60 kernel/locking/spinlock.c:178
       spin_lock_bh include/linux/spinlock.h:356 [inline]
       nr_remove_neigh+0x30/0xec net/netrom/nr_route.c:307
       nr_add_node+0x1754/0x1ea0 net/netrom/nr_route.c:249
       nr_rt_ioctl+0xc6c/0xf28 net/netrom/nr_route.c:651
       nr_ioctl+0x19c/0x474 net/netrom/af_netrom.c:1254
       sock_do_ioctl+0x134/0x2d0 net/socket.c:1209
       sock_ioctl+0x4ec/0x838 net/socket.c:1328
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:906 [inline]
       __se_sys_ioctl fs/ioctl.c:892 [inline]
       __arm64_sys_ioctl+0x14c/0x1cc fs/ioctl.c:892
       __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
       invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:49
       el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132
       do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151
       el0_svc+0x54/0x168 arch/arm64/kernel/entry-common.c:744
       el0t_64_sync_handler+0x84/0x108 arch/arm64/kernel/entry-common.c:762
       el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:600

-> #0 (&nr_node->node_lock){+...}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3163 [inline]
       check_prevs_add kernel/locking/lockdep.c:3282 [inline]
       validate_chain kernel/locking/lockdep.c:3906 [inline]
       __lock_acquire+0x34f0/0x7904 kernel/locking/lockdep.c:5228
       lock_acquire+0x23c/0x724 kernel/locking/lockdep.c:5851
       __raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline]
       _raw_spin_lock_bh+0x48/0x60 kernel/locking/spinlock.c:178
       spin_lock_bh include/linux/spinlock.h:356 [inline]
       nr_node_lock include/net/netrom.h:152 [inline]
       nr_rt_device_down+0x138/0x6f8 net/netrom/nr_route.c:519
       nr_device_event+0x138/0x164 net/netrom/af_netrom.c:126
       notifier_call_chain+0x1c4/0x550 kernel/notifier.c:85
       raw_notifier_call_chain+0x3c/0x50 kernel/notifier.c:453
       __dev_notify_flags+0x2c4/0x550
       dev_change_flags+0xd0/0x15c net/core/dev.c:9045
       dev_ifsioc+0xc8/0x904 net/core/dev_ioctl.c:526
       dev_ioctl+0x4d8/0xd34 net/core/dev_ioctl.c:783
       sock_do_ioctl+0x1d4/0x2d0 net/socket.c:1223
       sock_ioctl+0x4ec/0x838 net/socket.c:1328
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:906 [inline]
       __se_sys_ioctl fs/ioctl.c:892 [inline]
       __arm64_sys_ioctl+0x14c/0x1cc fs/ioctl.c:892
       __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
       invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:49
       el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132
       do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151
       el0_svc+0x54/0x168 arch/arm64/kernel/entry-common.c:744
       el0t_64_sync_handler+0x84/0x108 arch/arm64/kernel/entry-common.c:762
       el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:600

other info that might help us debug this:

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

 Possible unsafe locking scenario:

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

 *** DEADLOCK ***

3 locks held by syz.3.1882/10770:
 #0: ffff8000900fa5a8 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_lock+0x20/0x2c net/core/rtnetlink.c:79
 #1: ffff80009024b0f8 (nr_neigh_list_lock){+...}-{3:3}, at: spin_lock_bh include/linux/spinlock.h:356 [inline]
 #1: ffff80009024b0f8 (nr_neigh_list_lock){+...}-{3:3}, at: nr_rt_device_down+0x38/0x6f8 net/netrom/nr_route.c:514
 #2: ffff80009024b158 (nr_node_list_lock){+...}-{3:3}, at: spin_lock_bh include/linux/spinlock.h:356 [inline]
 #2: ffff80009024b158 (nr_node_list_lock){+...}-{3:3}, at: nr_rt_device_down+0xb8/0x6f8 net/netrom/nr_route.c:517

stack backtrace:
CPU: 1 UID: 0 PID: 10770 Comm: syz.3.1882 Not tainted 6.13.0-syzkaller-02526-gc4b9570cfb63 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 12/27/2024
Call trace:
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:466 (C)
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0xe4/0x150 lib/dump_stack.c:120
 dump_stack+0x1c/0x28 lib/dump_stack.c:129
 print_circular_bug+0x154/0x1c0 kernel/locking/lockdep.c:2076
 check_noncircular+0x310/0x404 kernel/locking/lockdep.c:2208
 check_prev_add kernel/locking/lockdep.c:3163 [inline]
 check_prevs_add kernel/locking/lockdep.c:3282 [inline]
 validate_chain kernel/locking/lockdep.c:3906 [inline]
 __lock_acquire+0x34f0/0x7904 kernel/locking/lockdep.c:5228
 lock_acquire+0x23c/0x724 kernel/locking/lockdep.c:5851
 __raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline]
 _raw_spin_lock_bh+0x48/0x60 kernel/locking/spinlock.c:178
 spin_lock_bh include/linux/spinlock.h:356 [inline]
 nr_node_lock include/net/netrom.h:152 [inline]
 nr_rt_device_down+0x138/0x6f8 net/netrom/nr_route.c:519
 nr_device_event+0x138/0x164 net/netrom/af_netrom.c:126
 notifier_call_chain+0x1c4/0x550 kernel/notifier.c:85
 raw_notifier_call_chain+0x3c/0x50 kernel/notifier.c:453
 __dev_notify_flags+0x2c4/0x550
 dev_change_flags+0xd0/0x15c net/core/dev.c:9045
 dev_ifsioc+0xc8/0x904 net/core/dev_ioctl.c:526
 dev_ioctl+0x4d8/0xd34 net/core/dev_ioctl.c:783
 sock_do_ioctl+0x1d4/0x2d0 net/socket.c:1223
 sock_ioctl+0x4ec/0x838 net/socket.c:1328
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:906 [inline]
 __se_sys_ioctl fs/ioctl.c:892 [inline]
 __arm64_sys_ioctl+0x14c/0x1cc fs/ioctl.c:892
 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
 invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:49
 el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132
 do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151
 el0_svc+0x54/0x168 arch/arm64/kernel/entry-common.c:744
 el0t_64_sync_handler+0x84/0x108 arch/arm64/kernel/entry-common.c:762
 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:600