netlink: 4 bytes leftover after parsing attributes in process `syz.2.494'. ====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ syz.2.494/5850 is trying to acquire lock: ffff800017875618 (nr_node_list_lock){+...}-{2:2}, at: spin_lock_bh include/linux/spinlock.h:356 [inline] ffff800017875618 (nr_node_list_lock){+...}-{2:2}, at: nr_rt_device_down+0xb4/0x660 net/netrom/nr_route.c:517 but task is already holding lock: ffff8000178755b8 (nr_neigh_list_lock){+...}-{2:2}, at: spin_lock_bh include/linux/spinlock.h:356 [inline] ffff8000178755b8 (nr_neigh_list_lock){+...}-{2:2}, at: nr_rt_device_down+0x38/0x660 net/netrom/nr_route.c:514 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (nr_neigh_list_lock){+...}-{2:2}: __raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline] _raw_spin_lock_bh+0x54/0x6c kernel/locking/spinlock.c:178 spin_lock_bh include/linux/spinlock.h:356 [inline] nr_remove_neigh net/netrom/nr_route.c:307 [inline] nr_dec_obs net/netrom/nr_route.c:472 [inline] nr_rt_ioctl+0x308/0xb80 net/netrom/nr_route.c:692 nr_ioctl+0x1c4/0x4e4 net/netrom/af_netrom.c:1254 sock_do_ioctl+0xf8/0x240 net/socket.c:1204 sock_ioctl+0x5c4/0x840 net/socket.c:1321 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:870 [inline] __se_sys_ioctl fs/ioctl.c:856 [inline] __arm64_sys_ioctl+0x14c/0x1c8 fs/ioctl.c:856 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline] invoke_syscall+0x98/0x2bc arch/arm64/kernel/syscall.c:52 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140 do_el0_svc+0x58/0x13c arch/arm64/kernel/syscall.c:204 el0_svc+0x58/0x138 arch/arm64/kernel/entry-common.c:637 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585 -> #1 (&nr_node->node_lock){+...}-{2:2}: __raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline] _raw_spin_lock_bh+0x54/0x6c kernel/locking/spinlock.c:178 spin_lock_bh include/linux/spinlock.h:356 [inline] nr_node_lock include/net/netrom.h:152 [inline] nr_dec_obs net/netrom/nr_route.c:459 [inline] nr_rt_ioctl+0x19c/0xb80 net/netrom/nr_route.c:692 nr_ioctl+0x1c4/0x4e4 net/netrom/af_netrom.c:1254 sock_do_ioctl+0xf8/0x240 net/socket.c:1204 sock_ioctl+0x5c4/0x840 net/socket.c:1321 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:870 [inline] __se_sys_ioctl fs/ioctl.c:856 [inline] __arm64_sys_ioctl+0x14c/0x1c8 fs/ioctl.c:856 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline] invoke_syscall+0x98/0x2bc arch/arm64/kernel/syscall.c:52 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140 do_el0_svc+0x58/0x13c arch/arm64/kernel/syscall.c:204 el0_svc+0x58/0x138 arch/arm64/kernel/entry-common.c:637 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585 -> #0 (nr_node_list_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+0x293c/0x6544 kernel/locking/lockdep.c:5049 lock_acquire+0x20c/0x644 kernel/locking/lockdep.c:5662 __raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline] _raw_spin_lock_bh+0x54/0x6c kernel/locking/spinlock.c:178 spin_lock_bh include/linux/spinlock.h:356 [inline] nr_rt_device_down+0xb4/0x660 net/netrom/nr_route.c:517 nr_device_event+0x138/0x164 net/netrom/af_netrom.c:126 notifier_call_chain kernel/notifier.c:87 [inline] raw_notifier_call_chain+0xd4/0x164 kernel/notifier.c:455 call_netdevice_notifiers_info net/core/dev.c:2001 [inline] call_netdevice_notifiers_extack net/core/dev.c:2039 [inline] call_netdevice_notifiers net/core/dev.c:2053 [inline] dev_close_many+0x2cc/0x440 net/core/dev.c:1601 dev_close+0x148/0x1f8 net/core/dev.c:1623 bpq_device_event+0x318/0x82c drivers/net/hamradio/bpqether.c:547 notifier_call_chain kernel/notifier.c:87 [inline] raw_notifier_call_chain+0xd4/0x164 kernel/notifier.c:455 call_netdevice_notifiers_info net/core/dev.c:2001 [inline] call_netdevice_notifiers_extack net/core/dev.c:2039 [inline] call_netdevice_notifiers net/core/dev.c:2053 [inline] dev_close_many+0x2cc/0x440 net/core/dev.c:1601 dev_close+0x148/0x1f8 net/core/dev.c:1623 bond_setup_by_slave+0x70/0x374 drivers/net/bonding/bond_main.c:1541 bond_enslave+0x628/0x2ed8 drivers/net/bonding/bond_main.c:1925 bond_do_ioctl+0x700/0xb18 drivers/net/bonding/bond_main.c:4592 bond_siocdevprivate+0x18c/0x1dc drivers/net/bonding/bond_main.c:-1 dev_siocdevprivate net/core/dev_ioctl.c:287 [inline] dev_ifsioc+0xa68/0xed0 net/core/dev_ioctl.c:406 dev_ioctl+0x548/0xc8c net/core/dev_ioctl.c:613 sock_ioctl+0x7a4/0x840 net/socket.c:1248 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:870 [inline] __se_sys_ioctl fs/ioctl.c:856 [inline] __arm64_sys_ioctl+0x14c/0x1c8 fs/ioctl.c:856 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline] invoke_syscall+0x98/0x2bc arch/arm64/kernel/syscall.c:52 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140 do_el0_svc+0x58/0x13c arch/arm64/kernel/syscall.c:204 el0_svc+0x58/0x138 arch/arm64/kernel/entry-common.c:637 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585 other info that might help us debug this: Chain exists of: nr_node_list_lock --> &nr_node->node_lock --> nr_neigh_list_lock Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(nr_neigh_list_lock); lock(&nr_node->node_lock); lock(nr_neigh_list_lock); lock(nr_node_list_lock); *** DEADLOCK *** 2 locks held by syz.2.494/5850: #0: ffff800017730708 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock+0x20/0x2c net/core/rtnetlink.c:74 #1: ffff8000178755b8 (nr_neigh_list_lock){+...}-{2:2}, at: spin_lock_bh include/linux/spinlock.h:356 [inline] #1: ffff8000178755b8 (nr_neigh_list_lock){+...}-{2:2}, at: nr_rt_device_down+0x38/0x660 net/netrom/nr_route.c:514 stack backtrace: CPU: 0 PID: 5850 Comm: syz.2.494 Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/30/2025 Call trace: dump_backtrace+0x1c8/0x1f4 arch/arm64/kernel/stacktrace.c:158 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:165 __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:2048 check_noncircular+0x240/0x2d4 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+0x293c/0x6544 kernel/locking/lockdep.c:5049 lock_acquire+0x20c/0x644 kernel/locking/lockdep.c:5662 __raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline] _raw_spin_lock_bh+0x54/0x6c kernel/locking/spinlock.c:178 spin_lock_bh include/linux/spinlock.h:356 [inline] nr_rt_device_down+0xb4/0x660 net/netrom/nr_route.c:517 nr_device_event+0x138/0x164 net/netrom/af_netrom.c:126 notifier_call_chain kernel/notifier.c:87 [inline] raw_notifier_call_chain+0xd4/0x164 kernel/notifier.c:455 call_netdevice_notifiers_info net/core/dev.c:2001 [inline] call_netdevice_notifiers_extack net/core/dev.c:2039 [inline] call_netdevice_notifiers net/core/dev.c:2053 [inline] dev_close_many+0x2cc/0x440 net/core/dev.c:1601 dev_close+0x148/0x1f8 net/core/dev.c:1623 bpq_device_event+0x318/0x82c drivers/net/hamradio/bpqether.c:547 notifier_call_chain kernel/notifier.c:87 [inline] raw_notifier_call_chain+0xd4/0x164 kernel/notifier.c:455 call_netdevice_notifiers_info net/core/dev.c:2001 [inline] call_netdevice_notifiers_extack net/core/dev.c:2039 [inline] call_netdevice_notifiers net/core/dev.c:2053 [inline] dev_close_many+0x2cc/0x440 net/core/dev.c:1601 dev_close+0x148/0x1f8 net/core/dev.c:1623 bond_setup_by_slave+0x70/0x374 drivers/net/bonding/bond_main.c:1541 bond_enslave+0x628/0x2ed8 drivers/net/bonding/bond_main.c:1925 bond_do_ioctl+0x700/0xb18 drivers/net/bonding/bond_main.c:4592 bond_siocdevprivate+0x18c/0x1dc drivers/net/bonding/bond_main.c:-1 dev_siocdevprivate net/core/dev_ioctl.c:287 [inline] dev_ifsioc+0xa68/0xed0 net/core/dev_ioctl.c:406 dev_ioctl+0x548/0xc8c net/core/dev_ioctl.c:613 sock_ioctl+0x7a4/0x840 net/socket.c:1248 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:870 [inline] __se_sys_ioctl fs/ioctl.c:856 [inline] __arm64_sys_ioctl+0x14c/0x1c8 fs/ioctl.c:856 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline] invoke_syscall+0x98/0x2bc arch/arm64/kernel/syscall.c:52 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140 do_el0_svc+0x58/0x13c arch/arm64/kernel/syscall.c:204 el0_svc+0x58/0x138 arch/arm64/kernel/entry-common.c:637 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585 8021q: adding VLAN 0 to HW filter on device bond0 bond0: (slave rose0): Enslaving as an active interface with an up link