====================================================== WARNING: possible circular locking dependency detected 5.15.182-syzkaller #0 Not tainted ------------------------------------------------------ syz.0.370/5587 is trying to acquire lock: ffff0000cce7f670 (&nr_node->node_lock){+...}-{2:2}, at: spin_lock_bh include/linux/spinlock.h:368 [inline] ffff0000cce7f670 (&nr_node->node_lock){+...}-{2:2}, at: nr_node_lock include/net/netrom.h:151 [inline] ffff0000cce7f670 (&nr_node->node_lock){+...}-{2:2}, at: nr_rt_device_down+0x12c/0x690 net/netrom/nr_route.c:519 but task is already holding lock: ffff8000163aa458 (nr_node_list_lock){+...}-{2:2}, at: spin_lock_bh include/linux/spinlock.h:368 [inline] ffff8000163aa458 (nr_node_list_lock){+...}-{2:2}, at: nr_rt_device_down+0xb4/0x690 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){+...}-{2:2}: __raw_spin_lock_bh include/linux/spinlock_api_smp.h:135 [inline] _raw_spin_lock_bh+0x114/0x1b4 kernel/locking/spinlock.c:178 spin_lock_bh include/linux/spinlock.h:368 [inline] nr_rt_device_down+0xb4/0x690 net/netrom/nr_route.c:517 nr_device_event+0x138/0x164 net/netrom/af_netrom.c:126 notifier_call_chain kernel/notifier.c:83 [inline] raw_notifier_call_chain+0xd4/0x164 kernel/notifier.c:391 call_netdevice_notifiers_info net/core/dev.c:2049 [inline] call_netdevice_notifiers_extack net/core/dev.c:2061 [inline] call_netdevice_notifiers net/core/dev.c:2075 [inline] __dev_notify_flags+0x250/0x46c net/core/dev.c:-1 dev_change_flags+0xc8/0x154 net/core/dev.c:8929 dev_ifsioc+0x504/0xef4 net/core/dev_ioctl.c:324 dev_ioctl+0x4d0/0xc94 net/core/dev_ioctl.c:587 sock_do_ioctl+0x18c/0x240 net/socket.c:1154 sock_ioctl+0x5c8/0x87c net/socket.c:1257 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:874 [inline] __se_sys_ioctl fs/ioctl.c:860 [inline] __arm64_sys_ioctl+0x14c/0x1c8 fs/ioctl.c:860 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline] invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142 do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181 el0_svc+0x78/0x1e0 arch/arm64/kernel/entry-common.c:608 el0t_64_sync_handler+0xcc/0xe4 arch/arm64/kernel/entry-common.c:626 el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584 -> #1 (nr_neigh_list_lock){+...}-{2:2}: __raw_spin_lock_bh include/linux/spinlock_api_smp.h:135 [inline] _raw_spin_lock_bh+0x114/0x1b4 kernel/locking/spinlock.c:178 spin_lock_bh include/linux/spinlock.h:368 [inline] nr_remove_neigh+0x30/0xec net/netrom/nr_route.c:307 nr_add_node+0x198c/0x21a0 net/netrom/nr_route.c:249 nr_rt_ioctl+0xc04/0xe2c net/netrom/nr_route.c:651 nr_ioctl+0x1c4/0x51c net/netrom/af_netrom.c:1253 sock_do_ioctl+0xf8/0x240 net/socket.c:1140 sock_ioctl+0x5c8/0x87c net/socket.c:1257 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:874 [inline] __se_sys_ioctl fs/ioctl.c:860 [inline] __arm64_sys_ioctl+0x14c/0x1c8 fs/ioctl.c:860 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline] invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142 do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181 el0_svc+0x78/0x1e0 arch/arm64/kernel/entry-common.c:608 el0t_64_sync_handler+0xcc/0xe4 arch/arm64/kernel/entry-common.c:626 el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584 -> #0 (&nr_node->node_lock){+...}-{2:2}: check_prev_add kernel/locking/lockdep.c:3053 [inline] check_prevs_add kernel/locking/lockdep.c:3172 [inline] validate_chain kernel/locking/lockdep.c:3788 [inline] __lock_acquire+0x2928/0x651c kernel/locking/lockdep.c:5012 lock_acquire+0x1f4/0x620 kernel/locking/lockdep.c:5623 __raw_spin_lock_bh include/linux/spinlock_api_smp.h:135 [inline] _raw_spin_lock_bh+0x114/0x1b4 kernel/locking/spinlock.c:178 spin_lock_bh include/linux/spinlock.h:368 [inline] nr_node_lock include/net/netrom.h:151 [inline] nr_rt_device_down+0x12c/0x690 net/netrom/nr_route.c:519 nr_device_event+0x138/0x164 net/netrom/af_netrom.c:126 notifier_call_chain kernel/notifier.c:83 [inline] raw_notifier_call_chain+0xd4/0x164 kernel/notifier.c:391 call_netdevice_notifiers_info net/core/dev.c:2049 [inline] call_netdevice_notifiers_extack net/core/dev.c:2061 [inline] call_netdevice_notifiers net/core/dev.c:2075 [inline] __dev_notify_flags+0x250/0x46c net/core/dev.c:-1 dev_change_flags+0xc8/0x154 net/core/dev.c:8929 dev_ifsioc+0x504/0xef4 net/core/dev_ioctl.c:324 dev_ioctl+0x4d0/0xc94 net/core/dev_ioctl.c:587 sock_do_ioctl+0x18c/0x240 net/socket.c:1154 sock_ioctl+0x5c8/0x87c net/socket.c:1257 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:874 [inline] __se_sys_ioctl fs/ioctl.c:860 [inline] __arm64_sys_ioctl+0x14c/0x1c8 fs/ioctl.c:860 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline] invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142 do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181 el0_svc+0x78/0x1e0 arch/arm64/kernel/entry-common.c:608 el0t_64_sync_handler+0xcc/0xe4 arch/arm64/kernel/entry-common.c:626 el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584 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.0.370/5587: #0: ffff800016277d68 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock+0x20/0x2c net/core/rtnetlink.c:72 #1: ffff8000163aa3f8 (nr_neigh_list_lock){+...}-{2:2}, at: spin_lock_bh include/linux/spinlock.h:368 [inline] #1: ffff8000163aa3f8 (nr_neigh_list_lock){+...}-{2:2}, at: nr_rt_device_down+0x38/0x690 net/netrom/nr_route.c:514 #2: ffff8000163aa458 (nr_node_list_lock){+...}-{2:2}, at: spin_lock_bh include/linux/spinlock.h:368 [inline] #2: ffff8000163aa458 (nr_node_list_lock){+...}-{2:2}, at: nr_rt_device_down+0xb4/0x690 net/netrom/nr_route.c:517 stack backtrace: CPU: 1 PID: 5587 Comm: syz.0.370 Not tainted 5.15.182-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/19/2025 Call trace: dump_backtrace+0x0/0x43c arch/arm64/kernel/stacktrace.c:152 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:216 __dump_stack+0x30/0x40 lib/dump_stack.c:88 dump_stack_lvl+0xf8/0x160 lib/dump_stack.c:106 dump_stack+0x1c/0x5c lib/dump_stack.c:113 print_circular_bug+0x148/0x1b0 kernel/locking/lockdep.c:2011 check_noncircular+0x240/0x2d4 kernel/locking/lockdep.c:2133 check_prev_add kernel/locking/lockdep.c:3053 [inline] check_prevs_add kernel/locking/lockdep.c:3172 [inline] validate_chain kernel/locking/lockdep.c:3788 [inline] __lock_acquire+0x2928/0x651c kernel/locking/lockdep.c:5012 lock_acquire+0x1f4/0x620 kernel/locking/lockdep.c:5623 __raw_spin_lock_bh include/linux/spinlock_api_smp.h:135 [inline] _raw_spin_lock_bh+0x114/0x1b4 kernel/locking/spinlock.c:178 spin_lock_bh include/linux/spinlock.h:368 [inline] nr_node_lock include/net/netrom.h:151 [inline] nr_rt_device_down+0x12c/0x690 net/netrom/nr_route.c:519 nr_device_event+0x138/0x164 net/netrom/af_netrom.c:126 notifier_call_chain kernel/notifier.c:83 [inline] raw_notifier_call_chain+0xd4/0x164 kernel/notifier.c:391 call_netdevice_notifiers_info net/core/dev.c:2049 [inline] call_netdevice_notifiers_extack net/core/dev.c:2061 [inline] call_netdevice_notifiers net/core/dev.c:2075 [inline] __dev_notify_flags+0x250/0x46c net/core/dev.c:-1 dev_change_flags+0xc8/0x154 net/core/dev.c:8929 dev_ifsioc+0x504/0xef4 net/core/dev_ioctl.c:324 dev_ioctl+0x4d0/0xc94 net/core/dev_ioctl.c:587 sock_do_ioctl+0x18c/0x240 net/socket.c:1154 sock_ioctl+0x5c8/0x87c net/socket.c:1257 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:874 [inline] __se_sys_ioctl fs/ioctl.c:860 [inline] __arm64_sys_ioctl+0x14c/0x1c8 fs/ioctl.c:860 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline] invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142 do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181 el0_svc+0x78/0x1e0 arch/arm64/kernel/entry-common.c:608 el0t_64_sync_handler+0xcc/0xe4 arch/arm64/kernel/entry-common.c:626 el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584