====================================================== WARNING: possible circular locking dependency detected 6.16.0-rc1-syzkaller-00101-g27605c8c0f69 #0 Not tainted ------------------------------------------------------ syz.4.1178/10619 is trying to acquire lock: ffffffff905a26b8 (nr_neigh_list_lock){+...}-{3:3}, at: spin_lock_bh include/linux/spinlock.h:356 [inline] ffffffff905a26b8 (nr_neigh_list_lock){+...}-{3:3}, at: nr_remove_neigh net/netrom/nr_route.c:307 [inline] ffffffff905a26b8 (nr_neigh_list_lock){+...}-{3:3}, at: nr_dec_obs net/netrom/nr_route.c:472 [inline] ffffffff905a26b8 (nr_neigh_list_lock){+...}-{3:3}, at: nr_rt_ioctl+0xc66/0x29b0 net/netrom/nr_route.c:692 but task is already holding lock: ffff888061bdf470 (&nr_node->node_lock){+...}-{3:3}, at: spin_lock_bh include/linux/spinlock.h:356 [inline] ffff888061bdf470 (&nr_node->node_lock){+...}-{3:3}, at: nr_node_lock include/net/netrom.h:152 [inline] ffff888061bdf470 (&nr_node->node_lock){+...}-{3:3}, at: nr_dec_obs net/netrom/nr_route.c:459 [inline] ffff888061bdf470 (&nr_node->node_lock){+...}-{3:3}, at: nr_rt_ioctl+0x816/0x29b0 net/netrom/nr_route.c:692 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (&nr_node->node_lock){+...}-{3:3}: __raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline] _raw_spin_lock_bh+0x33/0x40 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+0x18e/0x810 net/netrom/nr_route.c:519 nr_device_event+0x126/0x170 net/netrom/af_netrom.c:126 notifier_call_chain+0xbc/0x410 kernel/notifier.c:85 call_netdevice_notifiers_info+0xbe/0x140 net/core/dev.c:2230 call_netdevice_notifiers_extack net/core/dev.c:2268 [inline] call_netdevice_notifiers net/core/dev.c:2282 [inline] __dev_notify_flags+0x1f7/0x2e0 net/core/dev.c:9499 netif_change_flags+0x108/0x160 net/core/dev.c:9526 dev_change_flags+0xba/0x250 net/core/dev_api.c:68 dev_ifsioc+0x1498/0x1f70 net/core/dev_ioctl.c:565 dev_ioctl+0x223/0x10e0 net/core/dev_ioctl.c:823 sock_do_ioctl+0x19d/0x280 net/socket.c:1204 sock_ioctl+0x227/0x6b0 net/socket.c:1311 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:907 [inline] __se_sys_ioctl fs/ioctl.c:893 [inline] __x64_sys_ioctl+0x18b/0x210 fs/ioctl.c:893 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #1 (nr_node_list_lock){+...}-{3:3}: __raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline] _raw_spin_lock_bh+0x33/0x40 kernel/locking/spinlock.c:178 spin_lock_bh include/linux/spinlock.h:356 [inline] nr_rt_device_down+0xd3/0x810 net/netrom/nr_route.c:517 nr_device_event+0x126/0x170 net/netrom/af_netrom.c:126 notifier_call_chain+0xbc/0x410 kernel/notifier.c:85 call_netdevice_notifiers_info+0xbe/0x140 net/core/dev.c:2230 call_netdevice_notifiers_extack net/core/dev.c:2268 [inline] call_netdevice_notifiers net/core/dev.c:2282 [inline] __dev_notify_flags+0x1f7/0x2e0 net/core/dev.c:9499 netif_change_flags+0x108/0x160 net/core/dev.c:9526 dev_change_flags+0xba/0x250 net/core/dev_api.c:68 dev_ifsioc+0x1498/0x1f70 net/core/dev_ioctl.c:565 dev_ioctl+0x223/0x10e0 net/core/dev_ioctl.c:823 sock_do_ioctl+0x19d/0x280 net/socket.c:1204 sock_ioctl+0x227/0x6b0 net/socket.c:1311 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:907 [inline] __se_sys_ioctl fs/ioctl.c:893 [inline] __x64_sys_ioctl+0x18b/0x210 fs/ioctl.c:893 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #0 (nr_neigh_list_lock){+...}-{3:3}: check_prev_add kernel/locking/lockdep.c:3168 [inline] check_prevs_add kernel/locking/lockdep.c:3287 [inline] validate_chain kernel/locking/lockdep.c:3911 [inline] __lock_acquire+0x126f/0x1c90 kernel/locking/lockdep.c:5240 lock_acquire kernel/locking/lockdep.c:5871 [inline] lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5828 __raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline] _raw_spin_lock_bh+0x33/0x40 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+0xc66/0x29b0 net/netrom/nr_route.c:692 nr_ioctl+0x19a/0x2e0 net/netrom/af_netrom.c:1254 sock_do_ioctl+0x115/0x280 net/socket.c:1190 sock_ioctl+0x227/0x6b0 net/socket.c:1311 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:907 [inline] __se_sys_ioctl fs/ioctl.c:893 [inline] __x64_sys_ioctl+0x18b/0x210 fs/ioctl.c:893 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f 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 *** 2 locks held by syz.4.1178/10619: #0: ffffffff905a2718 (nr_node_list_lock){+...}-{3:3}, at: spin_lock_bh include/linux/spinlock.h:356 [inline] #0: ffffffff905a2718 (nr_node_list_lock){+...}-{3:3}, at: nr_dec_obs net/netrom/nr_route.c:457 [inline] #0: ffffffff905a2718 (nr_node_list_lock){+...}-{3:3}, at: nr_rt_ioctl+0x766/0x29b0 net/netrom/nr_route.c:692 #1: ffff888061bdf470 (&nr_node->node_lock){+...}-{3:3}, at: spin_lock_bh include/linux/spinlock.h:356 [inline] #1: ffff888061bdf470 (&nr_node->node_lock){+...}-{3:3}, at: nr_node_lock include/net/netrom.h:152 [inline] #1: ffff888061bdf470 (&nr_node->node_lock){+...}-{3:3}, at: nr_dec_obs net/netrom/nr_route.c:459 [inline] #1: ffff888061bdf470 (&nr_node->node_lock){+...}-{3:3}, at: nr_rt_ioctl+0x816/0x29b0 net/netrom/nr_route.c:692 stack backtrace: CPU: 2 UID: 0 PID: 10619 Comm: syz.4.1178 Not tainted 6.16.0-rc1-syzkaller-00101-g27605c8c0f69 #0 PREEMPT(full) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014 Call Trace: __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120 print_circular_bug+0x275/0x350 kernel/locking/lockdep.c:2046 check_noncircular+0x14c/0x170 kernel/locking/lockdep.c:2178 check_prev_add kernel/locking/lockdep.c:3168 [inline] check_prevs_add kernel/locking/lockdep.c:3287 [inline] validate_chain kernel/locking/lockdep.c:3911 [inline] __lock_acquire+0x126f/0x1c90 kernel/locking/lockdep.c:5240 lock_acquire kernel/locking/lockdep.c:5871 [inline] lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5828 __raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline] _raw_spin_lock_bh+0x33/0x40 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+0xc66/0x29b0 net/netrom/nr_route.c:692 nr_ioctl+0x19a/0x2e0 net/netrom/af_netrom.c:1254 sock_do_ioctl+0x115/0x280 net/socket.c:1190 sock_ioctl+0x227/0x6b0 net/socket.c:1311 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:907 [inline] __se_sys_ioctl fs/ioctl.c:893 [inline] __x64_sys_ioctl+0x18b/0x210 fs/ioctl.c:893 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f752ef8e929 Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f752fd8f038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007f752f1b5fa0 RCX: 00007f752ef8e929 RDX: 0000000000000000 RSI: 00000000000089e2 RDI: 0000000000000004 RBP: 00007f752f010b39 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 0000000000000000 R14: 00007f752f1b5fa0 R15: 00007ffcc2c0a8f8