======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
dhcpcd/5296 is trying to acquire lock:
ffff8880375e1558 (_xmit_X25#2){+.-.}-{3:3}, at: spin_lock include/linux/spinlock.h:347 [inline]
ffff8880375e1558 (_xmit_X25#2){+.-.}-{3:3}, at: __netif_tx_lock include/linux/netdevice.h:4866 [inline]
ffff8880375e1558 (_xmit_X25#2){+.-.}-{3:3}, at: __dev_queue_xmit+0xe9d/0x3920 net/core/dev.c:5082

but task is already holding lock:
ffff88807a8049c0 (&lapb->lock){+.-.}-{3:3}, at: spin_lock_bh include/linux/spinlock.h:353 [inline]
ffff88807a8049c0 (&lapb->lock){+.-.}-{3:3}, at: lapb_device_event+0x187/0x680 net/lapb/lapb_iface.c:471

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (&lapb->lock){+.-.}-{3:3}:
       __raw_spin_lock_bh include/linux/spinlock_api_smp.h:182 [inline]
       _raw_spin_lock_bh+0x36/0x50 kernel/locking/spinlock.c:205
       spin_lock_bh include/linux/spinlock.h:353 [inline]
       lapb_connect_request+0xf5/0x270 net/lapb/lapb_iface.c:293
       lapbeth_xmit+0x133/0x260 drivers/net/wan/lapbether.c:205
       __netdev_start_xmit include/linux/netdevice.h:5457 [inline]
       netdev_start_xmit include/linux/netdevice.h:5466 [inline]
       xmit_one net/core/dev.c:4068 [inline]
       dev_hard_start_xmit+0x2cd/0x830 net/core/dev.c:4084
       __dev_queue_xmit+0x14d1/0x3920 net/core/dev.c:5088
       x25_write_internal+0x9e7/0xe60 net/x25/x25_subr.c:255
       x25_connect+0x51c/0x8f0 net/x25/af_x25.c:807
       connect_socket net/socket.c:2143 [inline]
       __sys_connect_file net/socket.c:2168 [inline]
       __sys_connect+0x316/0x450 net/socket.c:2185
       __do_sys_connect net/socket.c:2191 [inline]
       __se_sys_connect net/socket.c:2188 [inline]
       __x64_sys_connect+0x7a/0x90 net/socket.c:2188
       do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
       do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (&lapbeth->up_lock){+.-.}-{3:3}:
       __raw_spin_lock_bh include/linux/spinlock_api_smp.h:182 [inline]
       _raw_spin_lock_bh+0x36/0x50 kernel/locking/spinlock.c:205
       spin_lock_bh include/linux/spinlock.h:353 [inline]
       lapbeth_xmit+0x32/0x260 drivers/net/wan/lapbether.c:191
       __netdev_start_xmit include/linux/netdevice.h:5457 [inline]
       netdev_start_xmit include/linux/netdevice.h:5466 [inline]
       xmit_one net/core/dev.c:4068 [inline]
       dev_hard_start_xmit+0x2cd/0x830 net/core/dev.c:4084
       __dev_queue_xmit+0x14d1/0x3920 net/core/dev.c:5088
       dev_queue_xmit include/linux/netdevice.h:3485 [inline]
       tx+0x6b/0x190 drivers/block/aoe/aoenet.c:62
       kthread+0x1ed/0x420 drivers/block/aoe/aoecmd.c:1241
       kthread+0x38b/0x480 kernel/kthread.c:436
       ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #0 (_xmit_X25#2){+.-.}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3209 [inline]
       check_prevs_add kernel/locking/lockdep.c:3328 [inline]
       validate_chain kernel/locking/lockdep.c:3952 [inline]
       __lock_acquire+0x164c/0x2de0 kernel/locking/lockdep.c:5288
       lock_acquire+0x115/0x350 kernel/locking/lockdep.c:5942
       __raw_spin_lock include/linux/spinlock_api_smp.h:190 [inline]
       _raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:173
       spin_lock include/linux/spinlock.h:347 [inline]
       __netif_tx_lock include/linux/netdevice.h:4866 [inline]
       __dev_queue_xmit+0xe9d/0x3920 net/core/dev.c:5082
       neigh_output include/net/neighbour.h:554 [inline]
       ip_finish_output2+0xd12/0x1150 net/ipv4/ip_output.c:236
       NF_HOOK_COND include/linux/netfilter.h:314 [inline]
       ip_output+0x29f/0x450 net/ipv4/ip_output.c:437
       iptunnel_xmit+0x626/0xd10 net/ipv4/ip_tunnel_core.c:97
       ip_tunnel_xmit+0x1960/0x2040 net/ipv4/ip_tunnel.c:852
       __gre_xmit net/ipv4/ip_gre.c:488 [inline]
       gre_tap_xmit+0x543/0x760 net/ipv4/ip_gre.c:783
       __netdev_start_xmit include/linux/netdevice.h:5457 [inline]
       netdev_start_xmit include/linux/netdevice.h:5466 [inline]
       xmit_one net/core/dev.c:4068 [inline]
       dev_hard_start_xmit+0x2cd/0x830 net/core/dev.c:4084
       sch_direct_xmit+0x257/0x4c0 net/sched/sch_generic.c:411
       __dev_xmit_skb net/core/dev.c:4407 [inline]
       __dev_queue_xmit+0x179a/0x3920 net/core/dev.c:5046
       lapb_data_transmit+0x90/0xb0 net/lapb/lapb_iface.c:447
       lapb_transmit_buffer+0x163/0x200 net/lapb/lapb_out.c:149
       lapb_establish_data_link+0x89/0xe0 net/lapb/lapb_out.c:-1
       lapb_device_event+0x4eb/0x680 net/lapb/lapb_iface.c:-1
       notifier_call_chain+0x1a5/0x3d0 kernel/notifier.c:86
       call_netdevice_notifiers_extack net/core/dev.c:2351 [inline]
       call_netdevice_notifiers net/core/dev.c:2365 [inline]
       __dev_notify_flags+0x31e/0x510 net/core/dev.c:10051
       netif_change_flags+0xde/0x1b0 net/core/dev.c:10080
       dev_change_flags+0x128/0x260 net/core/dev_api.c:68
       devinet_ioctl+0x966/0x1c50 net/ipv4/devinet.c:1189
       inet_ioctl+0x42a/0x560 net/ipv4/af_inet.c:1007
       sock_do_ioctl+0x101/0x320 net/socket.c:1328
       sock_ioctl+0x57a/0x7e0 net/socket.c:1449
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:597 [inline]
       __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583
       do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
       do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

Chain exists of:
  _xmit_X25#2 --> &lapbeth->up_lock --> &lapb->lock

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&lapb->lock);
                               lock(&lapbeth->up_lock);
                               lock(&lapb->lock);
  lock(_xmit_X25#2);

 *** DEADLOCK ***

locks held by dhcpcd/5296: 7, last CPU#0:
 #0: ffffffff916937a0 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_net_lock include/linux/rtnetlink.h:134 [inline]
 #0: ffffffff916937a0 (rtnl_mutex){+.+.}-{4:4}, at: devinet_ioctl+0x2fb/0x1c50 net/ipv4/devinet.c:1110
 #1: ffff88807a8049c0 (&lapb->lock){+.-.}-{3:3}, at: spin_lock_bh include/linux/spinlock.h:353 [inline]
 #1: ffff88807a8049c0 (&lapb->lock){+.-.}-{3:3}, at: lapb_device_event+0x187/0x680 net/lapb/lapb_iface.c:471
 #2: ffffffff9015a300 (rcu_read_lock_bh){....}-{1:3}, at: local_bh_disable include/linux/bottom_half.h:20 [inline]
 #2: ffffffff9015a300 (rcu_read_lock_bh){....}-{1:3}, at: rcu_read_lock_bh include/linux/rcupdate.h:902 [inline]
 #2: ffffffff9015a300 (rcu_read_lock_bh){....}-{1:3}, at: __dev_queue_xmit+0x29b/0x3920 net/core/dev.c:5002
 #3: ffff88805062c228 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock#3){+...}-{3:3}, at: spin_trylock include/linux/spinlock.h:359 [inline]
 #3: ffff88805062c228 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock#3){+...}-{3:3}, at: qdisc_run_begin include/net/sch_generic.h:206 [inline]
 #3: ffff88805062c228 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock#3){+...}-{3:3}, at: __dev_xmit_skb net/core/dev.c:4394 [inline]
 #3: ffff88805062c228 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock#3){+...}-{3:3}, at: __dev_queue_xmit+0x114e/0x3920 net/core/dev.c:5046
 #4: ffffffff9015a2a0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:309 [inline]
 #4: ffffffff9015a2a0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline]
 #4: ffffffff9015a2a0 (rcu_read_lock){....}-{1:3}, at: ip_output+0x5a/0x450 net/ipv4/ip_output.c:432
 #5: ffffffff9015a2a0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:309 [inline]
 #5: ffffffff9015a2a0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline]
 #5: ffffffff9015a2a0 (rcu_read_lock){....}-{1:3}, at: ip_finish_output2+0x3de/0x1150 net/ipv4/ip_output.c:229
 #6: ffffffff9015a300 (rcu_read_lock_bh){....}-{1:3}, at: local_bh_disable include/linux/bottom_half.h:20 [inline]
 #6: ffffffff9015a300 (rcu_read_lock_bh){....}-{1:3}, at: rcu_read_lock_bh include/linux/rcupdate.h:902 [inline]
 #6: ffffffff9015a300 (rcu_read_lock_bh){....}-{1:3}, at: __dev_queue_xmit+0x29b/0x3920 net/core/dev.c:5002

stack backtrace:
CPU: 0 UID: 0 PID: 5296 Comm: dhcpcd Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/06/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_circular_bug+0x2e2/0x300 kernel/locking/lockdep.c:2087
 check_noncircular+0x12f/0x150 kernel/locking/lockdep.c:2219
 check_prev_add kernel/locking/lockdep.c:3209 [inline]
 check_prevs_add kernel/locking/lockdep.c:3328 [inline]
 validate_chain kernel/locking/lockdep.c:3952 [inline]
 __lock_acquire+0x164c/0x2de0 kernel/locking/lockdep.c:5288
 lock_acquire+0x115/0x350 kernel/locking/lockdep.c:5942
 __raw_spin_lock include/linux/spinlock_api_smp.h:190 [inline]
 _raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:173
 spin_lock include/linux/spinlock.h:347 [inline]
 __netif_tx_lock include/linux/netdevice.h:4866 [inline]
 __dev_queue_xmit+0xe9d/0x3920 net/core/dev.c:5082
 neigh_output include/net/neighbour.h:554 [inline]
 ip_finish_output2+0xd12/0x1150 net/ipv4/ip_output.c:236
 NF_HOOK_COND include/linux/netfilter.h:314 [inline]
 ip_output+0x29f/0x450 net/ipv4/ip_output.c:437
 iptunnel_xmit+0x626/0xd10 net/ipv4/ip_tunnel_core.c:97
 ip_tunnel_xmit+0x1960/0x2040 net/ipv4/ip_tunnel.c:852
 __gre_xmit net/ipv4/ip_gre.c:488 [inline]
 gre_tap_xmit+0x543/0x760 net/ipv4/ip_gre.c:783
 __netdev_start_xmit include/linux/netdevice.h:5457 [inline]
 netdev_start_xmit include/linux/netdevice.h:5466 [inline]
 xmit_one net/core/dev.c:4068 [inline]
 dev_hard_start_xmit+0x2cd/0x830 net/core/dev.c:4084
 sch_direct_xmit+0x257/0x4c0 net/sched/sch_generic.c:411
 __dev_xmit_skb net/core/dev.c:4407 [inline]
 __dev_queue_xmit+0x179a/0x3920 net/core/dev.c:5046
 lapb_data_transmit+0x90/0xb0 net/lapb/lapb_iface.c:447
 lapb_transmit_buffer+0x163/0x200 net/lapb/lapb_out.c:149
 lapb_establish_data_link+0x89/0xe0 net/lapb/lapb_out.c:-1
 lapb_device_event+0x4eb/0x680 net/lapb/lapb_iface.c:-1
 notifier_call_chain+0x1a5/0x3d0 kernel/notifier.c:86
 call_netdevice_notifiers_extack net/core/dev.c:2351 [inline]
 call_netdevice_notifiers net/core/dev.c:2365 [inline]
 __dev_notify_flags+0x31e/0x510 net/core/dev.c:10051
 netif_change_flags+0xde/0x1b0 net/core/dev.c:10080
 dev_change_flags+0x128/0x260 net/core/dev_api.c:68
 devinet_ioctl+0x966/0x1c50 net/ipv4/devinet.c:1189
 inet_ioctl+0x42a/0x560 net/ipv4/af_inet.c:1007
 sock_do_ioctl+0x101/0x320 net/socket.c:1328
 sock_ioctl+0x57a/0x7e0 net/socket.c:1449
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:597 [inline]
 __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fbf3cd23378
Code: 00 00 48 8d 44 24 08 48 89 54 24 e0 48 89 44 24 c0 48 8d 44 24 d0 48 89 44 24 c8 b8 10 00 00 00 c7 44 24 b8 10 00 00 00 0f 05 <89> c2 3d 00 f0 ff ff 77 07 89 d0 c3 0f 1f 40 00 48 8b 15 49 3a 0d
RSP: 002b:00007ffc7c240988 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000012 RCX: 00007fbf3cd23378
RDX: 00007ffc7c250b80 RSI: 0000000000008914 RDI: 0000000000000012
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffc7c260d20
R13: 00007fbf3cc23708 R14: 0000000000000028 R15: 0000000000008914
 </TASK>