====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ syz.7.3180/19413 is trying to acquire lock: ffff888074b6fd70 (&nr_node->node_lock){+...}-{2:2}, at: spin_lock_bh include/linux/spinlock.h:356 [inline] ffff888074b6fd70 (&nr_node->node_lock){+...}-{2:2}, at: nr_node_lock include/net/netrom.h:152 [inline] ffff888074b6fd70 (&nr_node->node_lock){+...}-{2:2}, at: nr_rt_device_down+0x126/0x710 net/netrom/nr_route.c:519 but task is already holding lock: ffffffff8de93bd8 (nr_node_list_lock){+...}-{2:2}, at: spin_lock_bh include/linux/spinlock.h:356 [inline] ffffffff8de93bd8 (nr_node_list_lock){+...}-{2:2}, at: nr_rt_device_down+0xa5/0x710 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:126 [inline] _raw_spin_lock_bh+0x32/0x50 kernel/locking/spinlock.c:178 spin_lock_bh include/linux/spinlock.h:356 [inline] nr_rt_device_down+0xa5/0x710 net/netrom/nr_route.c:517 nr_device_event+0x133/0x140 net/netrom/af_netrom.c:126 notifier_call_chain kernel/notifier.c:87 [inline] raw_notifier_call_chain+0xcb/0x160 kernel/notifier.c:455 call_netdevice_notifiers_extack net/core/dev.c:2039 [inline] call_netdevice_notifiers net/core/dev.c:2053 [inline] __dev_notify_flags+0x158/0x300 net/core/dev.c:8678 dev_change_flags+0xe3/0x1a0 net/core/dev.c:8714 dev_ifsioc+0x130/0xd40 net/core/dev_ioctl.c:326 dev_ioctl+0x55e/0xe80 net/core/dev_ioctl.c:572 sock_do_ioctl+0x245/0x320 net/socket.c:1215 sock_ioctl+0x4d2/0x710 net/socket.c:1320 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:870 [inline] __se_sys_ioctl+0xfa/0x170 fs/ioctl.c:856 do_syscall_x64 arch/x86/entry/common.c:46 [inline] do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76 entry_SYSCALL_64_after_hwframe+0x68/0xd2 -> #1 (nr_neigh_list_lock){+...}-{2:2}: __raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline] _raw_spin_lock_bh+0x32/0x50 kernel/locking/spinlock.c:178 spin_lock_bh include/linux/spinlock.h:356 [inline] nr_remove_neigh+0x25/0xe0 net/netrom/nr_route.c:307 nr_add_node+0x1d2d/0x24b0 net/netrom/nr_route.c:249 nr_rt_ioctl+0xca9/0xde0 net/netrom/nr_route.c:651 sock_do_ioctl+0xfb/0x320 net/socket.c:1201 sock_ioctl+0x4d2/0x710 net/socket.c:1320 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:870 [inline] __se_sys_ioctl+0xfa/0x170 fs/ioctl.c:856 do_syscall_x64 arch/x86/entry/common.c:46 [inline] do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76 entry_SYSCALL_64_after_hwframe+0x68/0xd2 -> #0 (&nr_node->node_lock){+...}-{2:2}: check_prev_add kernel/locking/lockdep.c:3090 [inline] check_prevs_add kernel/locking/lockdep.c:3209 [inline] validate_chain kernel/locking/lockdep.c:3825 [inline] __lock_acquire+0x2d07/0x7d10 kernel/locking/lockdep.c:5049 lock_acquire+0x1bb/0x4a0 kernel/locking/lockdep.c:5662 __raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline] _raw_spin_lock_bh+0x32/0x50 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+0x126/0x710 net/netrom/nr_route.c:519 nr_device_event+0x133/0x140 net/netrom/af_netrom.c:126 notifier_call_chain kernel/notifier.c:87 [inline] raw_notifier_call_chain+0xcb/0x160 kernel/notifier.c:455 call_netdevice_notifiers_extack net/core/dev.c:2039 [inline] call_netdevice_notifiers net/core/dev.c:2053 [inline] __dev_notify_flags+0x158/0x300 net/core/dev.c:8678 dev_change_flags+0xe3/0x1a0 net/core/dev.c:8714 dev_ifsioc+0x130/0xd40 net/core/dev_ioctl.c:326 dev_ioctl+0x55e/0xe80 net/core/dev_ioctl.c:572 sock_do_ioctl+0x245/0x320 net/socket.c:1215 sock_ioctl+0x4d2/0x710 net/socket.c:1320 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:870 [inline] __se_sys_ioctl+0xfa/0x170 fs/ioctl.c:856 do_syscall_x64 arch/x86/entry/common.c:46 [inline] do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76 entry_SYSCALL_64_after_hwframe+0x68/0xd2 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.7.3180/19413: #0: ffffffff8dd45ba8 (rtnl_mutex){+.+.}-{3:3}, at: dev_ioctl+0x54d/0xe80 net/core/dev_ioctl.c:571 #1: ffffffff8de93b78 (nr_neigh_list_lock){+...}-{2:2}, at: spin_lock_bh include/linux/spinlock.h:356 [inline] #1: ffffffff8de93b78 (nr_neigh_list_lock){+...}-{2:2}, at: nr_rt_device_down+0x24/0x710 net/netrom/nr_route.c:514 #2: ffffffff8de93bd8 (nr_node_list_lock){+...}-{2:2}, at: spin_lock_bh include/linux/spinlock.h:356 [inline] #2: ffffffff8de93bd8 (nr_node_list_lock){+...}-{2:2}, at: nr_rt_device_down+0xa5/0x710 net/netrom/nr_route.c:517 stack backtrace: CPU: 1 PID: 19413 Comm: syz.7.3180 Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025 Call Trace: dump_stack_lvl+0x188/0x24e lib/dump_stack.c:106 check_noncircular+0x296/0x330 kernel/locking/lockdep.c:2170 check_prev_add kernel/locking/lockdep.c:3090 [inline] check_prevs_add kernel/locking/lockdep.c:3209 [inline] validate_chain kernel/locking/lockdep.c:3825 [inline] __lock_acquire+0x2d07/0x7d10 kernel/locking/lockdep.c:5049 lock_acquire+0x1bb/0x4a0 kernel/locking/lockdep.c:5662 __raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline] _raw_spin_lock_bh+0x32/0x50 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+0x126/0x710 net/netrom/nr_route.c:519 nr_device_event+0x133/0x140 net/netrom/af_netrom.c:126 notifier_call_chain kernel/notifier.c:87 [inline] raw_notifier_call_chain+0xcb/0x160 kernel/notifier.c:455 call_netdevice_notifiers_extack net/core/dev.c:2039 [inline] call_netdevice_notifiers net/core/dev.c:2053 [inline] __dev_notify_flags+0x158/0x300 net/core/dev.c:8678 dev_change_flags+0xe3/0x1a0 net/core/dev.c:8714 dev_ifsioc+0x130/0xd40 net/core/dev_ioctl.c:326 dev_ioctl+0x55e/0xe80 net/core/dev_ioctl.c:572 sock_do_ioctl+0x245/0x320 net/socket.c:1215 sock_ioctl+0x4d2/0x710 net/socket.c:1320 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:870 [inline] __se_sys_ioctl+0xfa/0x170 fs/ioctl.c:856 do_syscall_x64 arch/x86/entry/common.c:46 [inline] do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76 entry_SYSCALL_64_after_hwframe+0x68/0xd2 RIP: 0033:0x7efc14d9aeb9 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:00007efc15cb5028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007efc15016270 RCX: 00007efc14d9aeb9 RDX: 0000200000000000 RSI: 0000000000008914 RDI: 000000000000000a RBP: 00007efc14e08c1f R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007efc15016308 R14: 00007efc15016270 R15: 00007ffdab34f468