======================================================
WARNING: possible circular locking dependency detected
6.9.0-rc7-syzkaller-00183-gcf87f46fd34d #0 Not tainted
------------------------------------------------------
syz-executor.0/6299 is trying to acquire lock:
ffff80008f9bc578 (nr_neigh_list_lock){+...}-{2:2}, at: spin_lock_bh include/linux/spinlock.h:356 [inline]
ffff80008f9bc578 (nr_neigh_list_lock){+...}-{2:2}, at: nr_remove_neigh net/netrom/nr_route.c:315 [inline]
ffff80008f9bc578 (nr_neigh_list_lock){+...}-{2:2}, at: nr_del_node+0x344/0x850 net/netrom/nr_route.c:349

but task is already holding lock:
ffff0000cc469270 (&nr_node->node_lock){+...}-{2:2}, at: spin_lock_bh include/linux/spinlock.h:356 [inline]
ffff0000cc469270 (&nr_node->node_lock){+...}-{2:2}, at: nr_node_lock include/net/netrom.h:152 [inline]
ffff0000cc469270 (&nr_node->node_lock){+...}-{2:2}, at: nr_del_node+0xb4/0x850 net/netrom/nr_route.c:342

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (&nr_node->node_lock){+...}-{2:2}:
       __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+0x138/0x810 net/netrom/nr_route.c:524
       nr_device_event+0x138/0x164 net/netrom/af_netrom.c:126
       notifier_call_chain+0x1bc/0x540 kernel/notifier.c:93
       raw_notifier_call_chain+0x3c/0x50 kernel/notifier.c:461
       __dev_notify_flags+0x2c4/0x550
       dev_change_flags+0xd0/0x15c net/core/dev.c:8769
       dev_ifsioc+0xc8/0x904 net/core/dev_ioctl.c:530
       dev_ioctl+0x4d8/0xd34 net/core/dev_ioctl.c:787
       sock_do_ioctl+0x1d4/0x2d0 net/socket.c:1236
       sock_ioctl+0x4ec/0x838 net/socket.c:1341
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:904 [inline]
       __se_sys_ioctl fs/ioctl.c:890 [inline]
       __arm64_sys_ioctl+0x14c/0x1c8 fs/ioctl.c:890
       __invoke_syscall arch/arm64/kernel/syscall.c:34 [inline]
       invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:48
       el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:133
       do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:152
       el0_svc+0x54/0x168 arch/arm64/kernel/entry-common.c:712
       el0t_64_sync_handler+0x84/0xfc arch/arm64/kernel/entry-common.c:730
       el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:598

-> #1 (nr_node_list_lock){+...}-{2:2}:
       __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+0xc0/0x810 net/netrom/nr_route.c:522
       nr_device_event+0x138/0x164 net/netrom/af_netrom.c:126
       notifier_call_chain+0x1bc/0x540 kernel/notifier.c:93
       raw_notifier_call_chain+0x3c/0x50 kernel/notifier.c:461
       __dev_notify_flags+0x2c4/0x550
       dev_change_flags+0xd0/0x15c net/core/dev.c:8769
       dev_ifsioc+0xc8/0x904 net/core/dev_ioctl.c:530
       dev_ioctl+0x4d8/0xd34 net/core/dev_ioctl.c:787
       sock_do_ioctl+0x1d4/0x2d0 net/socket.c:1236
       sock_ioctl+0x4ec/0x838 net/socket.c:1341
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:904 [inline]
       __se_sys_ioctl fs/ioctl.c:890 [inline]
       __arm64_sys_ioctl+0x14c/0x1c8 fs/ioctl.c:890
       __invoke_syscall arch/arm64/kernel/syscall.c:34 [inline]
       invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:48
       el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:133
       do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:152
       el0_svc+0x54/0x168 arch/arm64/kernel/entry-common.c:712
       el0t_64_sync_handler+0x84/0xfc arch/arm64/kernel/entry-common.c:730
       el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:598

-> #0 (nr_neigh_list_lock){+...}-{2:2}:
       check_prev_add kernel/locking/lockdep.c:3134 [inline]
       check_prevs_add kernel/locking/lockdep.c:3253 [inline]
       validate_chain kernel/locking/lockdep.c:3869 [inline]
       __lock_acquire+0x3384/0x763c kernel/locking/lockdep.c:5137
       lock_acquire+0x248/0x73c kernel/locking/lockdep.c:5754
       __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 net/netrom/nr_route.c:315 [inline]
       nr_del_node+0x344/0x850 net/netrom/nr_route.c:349
       nr_rt_ioctl+0xa68/0x1050 net/netrom/nr_route.c:683
       nr_ioctl+0x14c/0x45c net/netrom/af_netrom.c:1254
       sock_do_ioctl+0x134/0x2d0 net/socket.c:1222
       sock_ioctl+0x4ec/0x838 net/socket.c:1341
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:904 [inline]
       __se_sys_ioctl fs/ioctl.c:890 [inline]
       __arm64_sys_ioctl+0x14c/0x1c8 fs/ioctl.c:890
       __invoke_syscall arch/arm64/kernel/syscall.c:34 [inline]
       invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:48
       el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:133
       do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:152
       el0_svc+0x54/0x168 arch/arm64/kernel/entry-common.c:712
       el0t_64_sync_handler+0x84/0xfc arch/arm64/kernel/entry-common.c:730
       el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:598

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-executor.0/6299:
 #0: ffff0000cc469270 (&nr_node->node_lock){+...}-{2:2}, at: spin_lock_bh include/linux/spinlock.h:356 [inline]
 #0: ffff0000cc469270 (&nr_node->node_lock){+...}-{2:2}, at: nr_node_lock include/net/netrom.h:152 [inline]
 #0: ffff0000cc469270 (&nr_node->node_lock){+...}-{2:2}, at: nr_del_node+0xb4/0x850 net/netrom/nr_route.c:342

stack backtrace:
CPU: 1 PID: 6299 Comm: syz-executor.0 Not tainted 6.9.0-rc7-syzkaller-00183-gcf87f46fd34d #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
Call trace:
 dump_backtrace+0x1b8/0x1e4 arch/arm64/kernel/stacktrace.c:317
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:324
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0xe4/0x150 lib/dump_stack.c:114
 dump_stack+0x1c/0x28 lib/dump_stack.c:123
 print_circular_bug+0x150/0x1b8 kernel/locking/lockdep.c:2060
 check_noncircular+0x310/0x404 kernel/locking/lockdep.c:2187
 check_prev_add kernel/locking/lockdep.c:3134 [inline]
 check_prevs_add kernel/locking/lockdep.c:3253 [inline]
 validate_chain kernel/locking/lockdep.c:3869 [inline]
 __lock_acquire+0x3384/0x763c kernel/locking/lockdep.c:5137
 lock_acquire+0x248/0x73c kernel/locking/lockdep.c:5754
 __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 net/netrom/nr_route.c:315 [inline]
 nr_del_node+0x344/0x850 net/netrom/nr_route.c:349
 nr_rt_ioctl+0xa68/0x1050 net/netrom/nr_route.c:683
 nr_ioctl+0x14c/0x45c net/netrom/af_netrom.c:1254
 sock_do_ioctl+0x134/0x2d0 net/socket.c:1222
 sock_ioctl+0x4ec/0x838 net/socket.c:1341
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:904 [inline]
 __se_sys_ioctl fs/ioctl.c:890 [inline]
 __arm64_sys_ioctl+0x14c/0x1c8 fs/ioctl.c:890
 __invoke_syscall arch/arm64/kernel/syscall.c:34 [inline]
 invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:48
 el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:133
 do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:152
 el0_svc+0x54/0x168 arch/arm64/kernel/entry-common.c:712
 el0t_64_sync_handler+0x84/0xfc arch/arm64/kernel/entry-common.c:730
 el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:598