======================================================
WARNING: possible circular locking dependency detected
6.13.0-rc6-syzkaller-g13563da6ffcf #0 Not tainted
------------------------------------------------------
syz.4.129/6959 is trying to acquire lock:
ffffffff8f34e0f8 (nr_node_list_lock){+...}-{3:3}, at: spin_lock_bh include/linux/spinlock.h:356 [inline]
ffffffff8f34e0f8 (nr_node_list_lock){+...}-{3:3}, at: nr_rt_device_down+0xb1/0x7b0 net/netrom/nr_route.c:517

but task is already holding lock:
ffffffff8f34e098 (nr_neigh_list_lock){+...}-{3:3}, at: spin_lock_bh include/linux/spinlock.h:356 [inline]
ffffffff8f34e098 (nr_neigh_list_lock){+...}-{3:3}, at: nr_rt_device_down+0x24/0x7b0 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){+...}-{3:3}:
       __raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline]
       _raw_spin_lock_bh+0x31/0x40 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+0x394/0xfb0 net/netrom/nr_route.c:692
       sock_do_ioctl+0x154/0x460 net/socket.c:1209
       sock_ioctl+0x622/0x8e0 net/socket.c:1328
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:906 [inline]
       __se_sys_ioctl+0xf5/0x170 fs/ioctl.c:892
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0x7e/0x180 arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x76/0x7e

-> #1 (&nr_node->node_lock){+...}-{3:3}:
       __raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline]
       _raw_spin_lock_bh+0x31/0x40 kernel/locking/spinlock.c:178
       spin_lock_bh include/linux/spinlock.h:356 [inline]
       nr_node_lock include/net/netrom.h:152 [inline]
       nr_dec_obs net/netrom/nr_route.c:459 [inline]
       nr_rt_ioctl+0x18e/0xfb0 net/netrom/nr_route.c:692
       sock_do_ioctl+0x154/0x460 net/socket.c:1209
       sock_ioctl+0x622/0x8e0 net/socket.c:1328
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:906 [inline]
       __se_sys_ioctl+0xf5/0x170 fs/ioctl.c:892
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0x7e/0x180 arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x76/0x7e

-> #0 (nr_node_list_lock){+...}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3161 [inline]
       check_prevs_add kernel/locking/lockdep.c:3280 [inline]
       validate_chain kernel/locking/lockdep.c:3904 [inline]
       __lock_acquire+0x3012/0x81c0 kernel/locking/lockdep.c:5226
       lock_acquire+0x1e9/0x540 kernel/locking/lockdep.c:5849
       __raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline]
       _raw_spin_lock_bh+0x31/0x40 kernel/locking/spinlock.c:178
       spin_lock_bh include/linux/spinlock.h:356 [inline]
       nr_rt_device_down+0xb1/0x7b0 net/netrom/nr_route.c:517
       nr_device_event+0x130/0x140 net/netrom/af_netrom.c:126
       notifier_call_chain+0x1a5/0x3e0 kernel/notifier.c:85
       __dev_notify_flags+0x203/0x400
       dev_change_flags+0xec/0x1a0 net/core/dev.c:9028
       dev_ifsioc+0x7c4/0xe70 net/core/dev_ioctl.c:526
       dev_ioctl+0x715/0x1340 net/core/dev_ioctl.c:783
       sock_do_ioctl+0x23c/0x460 net/socket.c:1223
       sock_ioctl+0x622/0x8e0 net/socket.c:1328
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:906 [inline]
       __se_sys_ioctl+0xf5/0x170 fs/ioctl.c:892
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0x7e/0x180 arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x76/0x7e

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.4.129/6959:
 #0: ffffffff8f1fc308 (rtnl_mutex){+.+.}-{4:4}, at: dev_ioctl+0x702/0x1340 net/core/dev_ioctl.c:782
 #1: ffffffff8f34e098 (nr_neigh_list_lock){+...}-{3:3}, at: spin_lock_bh include/linux/spinlock.h:356 [inline]
 #1: ffffffff8f34e098 (nr_neigh_list_lock){+...}-{3:3}, at: nr_rt_device_down+0x24/0x7b0 net/netrom/nr_route.c:514

stack backtrace:
CPU: 0 UID: 0 PID: 6959 Comm: syz.4.129 Not tainted 6.13.0-rc6-syzkaller-g13563da6ffcf #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x23d/0x360 lib/dump_stack.c:120
 print_circular_bug+0x13a/0x1b0 kernel/locking/lockdep.c:2074
 check_noncircular+0x375/0x4a0 kernel/locking/lockdep.c:2206
 check_prev_add kernel/locking/lockdep.c:3161 [inline]
 check_prevs_add kernel/locking/lockdep.c:3280 [inline]
 validate_chain kernel/locking/lockdep.c:3904 [inline]
 __lock_acquire+0x3012/0x81c0 kernel/locking/lockdep.c:5226
 lock_acquire+0x1e9/0x540 kernel/locking/lockdep.c:5849
 __raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline]
 _raw_spin_lock_bh+0x31/0x40 kernel/locking/spinlock.c:178
 spin_lock_bh include/linux/spinlock.h:356 [inline]
 nr_rt_device_down+0xb1/0x7b0 net/netrom/nr_route.c:517
 nr_device_event+0x130/0x140 net/netrom/af_netrom.c:126
 notifier_call_chain+0x1a5/0x3e0 kernel/notifier.c:85
 __dev_notify_flags+0x203/0x400
 dev_change_flags+0xec/0x1a0 net/core/dev.c:9028
 dev_ifsioc+0x7c4/0xe70 net/core/dev_ioctl.c:526
 dev_ioctl+0x715/0x1340 net/core/dev_ioctl.c:783
 sock_do_ioctl+0x23c/0x460 net/socket.c:1223
 sock_ioctl+0x622/0x8e0 net/socket.c:1328
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:906 [inline]
 __se_sys_ioctl+0xf5/0x170 fs/ioctl.c:892
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0x7e/0x180 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x76/0x7e
RIP: 0033:0x7feaccb85d29
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:00007feacd98d038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007feaccd75fa0 RCX: 00007feaccb85d29
RDX: 0000000020000000 RSI: 0000000000008914 RDI: 0000000000000007
RBP: 00007feaccc01b08 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007feaccd75fa0 R15: 00007ffd3b593ad8
 </TASK>