====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ dhcpcd-run-hook/7143 is trying to acquire lock: ffff88802afe6558 (_xmit_X25#2){+.-.}-{3:3}, at: spin_lock include/linux/spinlock.h:347 [inline] ffff88802afe6558 (_xmit_X25#2){+.-.}-{3:3}, at: __netif_tx_lock include/linux/netdevice.h:4841 [inline] ffff88802afe6558 (_xmit_X25#2){+.-.}-{3:3}, at: __dev_queue_xmit+0xe9d/0x3920 net/core/dev.c:4952 but task is already holding lock: ffff8880135c29c0 (&lapb->lock){+.-.}-{3:3}, at: spin_lock_bh include/linux/spinlock.h:353 [inline] ffff8880135c29c0 (&lapb->lock){+.-.}-{3:3}, at: lapb_t1timer_expiry+0x33/0xaa0 net/lapb/lapb_timer.c:99 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_data_received+0xfc/0x1c0 net/lapb/lapb_iface.c:398 lapbeth_rcv+0x34d/0x640 drivers/net/wan/lapbether.c:142 __netif_receive_skb_one_core net/core/dev.c:6297 [inline] __netif_receive_skb net/core/dev.c:6410 [inline] process_backlog+0xc26/0x18b0 net/core/dev.c:6761 __napi_poll+0xaa/0x330 net/core/dev.c:7830 napi_poll net/core/dev.c:7893 [inline] net_rx_action+0x61d/0xf50 net/core/dev.c:8050 handle_softirqs+0x226/0x860 kernel/softirq.c:645 do_softirq+0x77/0xd0 kernel/softirq.c:546 __local_bh_enable_ip+0x100/0x140 kernel/softirq.c:473 spin_unlock_bh include/linux/spinlock.h:407 [inline] lapb_device_event+0x4f3/0x680 net/lapb/lapb_iface.c:527 notifier_call_chain+0x1a5/0x3d0 kernel/notifier.c:85 call_netdevice_notifiers_extack net/core/dev.c:2313 [inline] call_netdevice_notifiers net/core/dev.c:2327 [inline] __dev_notify_flags+0x31e/0x510 net/core/dev.c:9896 netif_change_flags+0xde/0x1b0 net/core/dev.c:9925 dev_change_flags+0x128/0x260 net/core/dev_api.c:68 devinet_ioctl+0x966/0x1c50 net/ipv4/devinet.c:1199 inet_ioctl+0x42a/0x560 net/ipv4/af_inet.c:1010 sock_do_ioctl+0x101/0x320 net/socket.c:1325 sock_ioctl+0x57a/0x7e0 net/socket.c:1446 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 -> #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:5432 [inline] netdev_start_xmit include/linux/netdevice.h:5441 [inline] xmit_one net/core/dev.c:3953 [inline] dev_hard_start_xmit+0x2cd/0x830 net/core/dev.c:3969 __dev_queue_xmit+0x14d1/0x3920 net/core/dev.c:4958 dev_queue_xmit include/linux/netdevice.h:3464 [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:4841 [inline] __dev_queue_xmit+0xe9d/0x3920 net/core/dev.c:4952 neigh_output include/net/neighbour.h:560 [inline] ip_finish_output2+0xc4b/0x10b0 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 udp_tunnel_xmit_skb+0x29b/0x3e0 net/ipv4/udp_tunnel_core.c:187 vxlan_xmit_one+0x21f6/0x2eb0 drivers/net/vxlan/vxlan_core.c:2571 vxlan_xmit+0x1e19/0x33b0 drivers/net/vxlan/vxlan_core.c:2860 __netdev_start_xmit include/linux/netdevice.h:5432 [inline] netdev_start_xmit include/linux/netdevice.h:5441 [inline] xmit_one net/core/dev.c:3953 [inline] dev_hard_start_xmit+0x2cd/0x830 net/core/dev.c:3969 __dev_queue_xmit+0x14d1/0x3920 net/core/dev.c:4958 lapb_data_transmit+0x90/0xb0 net/lapb/lapb_iface.c:447 lapb_transmit_buffer+0x163/0x200 net/lapb/lapb_out.c:149 lapb_t1timer_expiry+0x68d/0xaa0 net/lapb/lapb_timer.c:-1 call_timer_fn+0x18d/0x5f0 kernel/time/timer.c:1748 expire_timers kernel/time/timer.c:1799 [inline] __run_timers kernel/time/timer.c:2374 [inline] __run_timer_base+0x652/0x8b0 kernel/time/timer.c:2386 run_timer_base kernel/time/timer.c:2395 [inline] run_timer_softirq+0xb7/0x170 kernel/time/timer.c:2405 handle_softirqs+0x226/0x860 kernel/softirq.c:645 __do_softirq kernel/softirq.c:679 [inline] invoke_softirq kernel/softirq.c:519 [inline] __irq_exit_rcu+0xcb/0x220 kernel/softirq.c:758 irq_exit_rcu+0x9/0x30 kernel/softirq.c:775 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1062 [inline] sysvec_apic_timer_interrupt+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1062 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:674 its_return_thunk+0x0/0x10 const_folio_flags include/linux/page-flags.h:345 [inline] folio_test_swapbacked include/linux/page-flags.h:572 [inline] mm_counter_file include/linux/mm.h:3489 [inline] mm_counter include/linux/mm.h:3498 [inline] zap_present_folio_ptes mm/memory.c:1789 [inline] zap_present_ptes mm/memory.c:1861 [inline] do_zap_pte_range mm/memory.c:1963 [inline] zap_pte_range mm/memory.c:2065 [inline] zap_pmd_range mm/memory.c:2151 [inline] zap_pud_range mm/memory.c:2179 [inline] zap_p4d_range mm/memory.c:2200 [inline] __zap_vma_range+0x216b/0x4f80 mm/memory.c:2240 unmap_vmas+0x390/0x550 mm/memory.c:2309 exit_mmap+0x293/0x9f0 mm/mmap.c:1315 __mmput+0x118/0x420 kernel/fork.c:1193 exit_mm+0x18e/0x240 kernel/exit.c:592 do_exit+0x6cd/0x2360 kernel/exit.c:974 do_group_exit+0x22d/0x2f0 kernel/exit.c:1129 __do_sys_exit_group kernel/exit.c:1140 [inline] __se_sys_exit_group kernel/exit.c:1138 [inline] __x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1138 x64_sys_call+0x18c6/0x18d0 arch/x86/include/generated/asm/syscalls_64.h:232 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-run-hook/7143: 11, last CPU#0: #0: ffff88807be3c080 (&mm->mmap_lock){++++}-{4:4}, at: mmap_read_lock include/linux/mmap_lock.h:600 [inline] #0: ffff88807be3c080 (&mm->mmap_lock){++++}-{4:4}, at: exit_mmap+0x1a4/0x9f0 mm/mmap.c:1299 #1: ffffffff8fd5cea0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:309 [inline] #1: ffffffff8fd5cea0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline] #1: ffffffff8fd5cea0 (rcu_read_lock){....}-{1:3}, at: __pte_offset_map+0x29/0x240 mm/pgtable-generic.c:290 #2: ffff8880744c99d8 (ptlock_ptr(ptdesc)#2){+.+.}-{3:3}, at: spin_lock include/linux/spinlock.h:347 [inline] #2: ffff8880744c99d8 (ptlock_ptr(ptdesc)#2){+.+.}-{3:3}, at: pte_offset_map_lock+0x13d/0x210 mm/pgtable-generic.c:404 #3: ffffc90000007cc0 ((&lapb->t1timer)){+.-.}-{0:0}, at: call_timer_fn+0xd5/0x5f0 kernel/time/timer.c:1745 #4: ffff8880135c29c0 (&lapb->lock){+.-.}-{3:3}, at: spin_lock_bh include/linux/spinlock.h:353 [inline] #4: ffff8880135c29c0 (&lapb->lock){+.-.}-{3:3}, at: lapb_t1timer_expiry+0x33/0xaa0 net/lapb/lapb_timer.c:99 #5: ffffffff8fd5cf00 (rcu_read_lock_bh){....}-{1:3}, at: local_bh_disable include/linux/bottom_half.h:20 [inline] #5: ffffffff8fd5cf00 (rcu_read_lock_bh){....}-{1:3}, at: rcu_read_lock_bh include/linux/rcupdate.h:902 [inline] #5: ffffffff8fd5cf00 (rcu_read_lock_bh){....}-{1:3}, at: __dev_queue_xmit+0x29b/0x3920 net/core/dev.c:4872 #6: ffffffff8fd5cea0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:309 [inline] #6: ffffffff8fd5cea0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline] #6: ffffffff8fd5cea0 (rcu_read_lock){....}-{1:3}, at: vxlan_xmit+0x175d/0x33b0 drivers/net/vxlan/vxlan_core.c:2816 #7: ffffffff8fd5cea0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:309 [inline] #7: ffffffff8fd5cea0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline] #7: ffffffff8fd5cea0 (rcu_read_lock){....}-{1:3}, at: vxlan_xmit_one+0x1407/0x2eb0 drivers/net/vxlan/vxlan_core.c:2489 #8: ffffffff8fd5cea0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:309 [inline] #8: ffffffff8fd5cea0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline] #8: ffffffff8fd5cea0 (rcu_read_lock){....}-{1:3}, at: ip_output+0x5a/0x450 net/ipv4/ip_output.c:432 #9: ffffffff8fd5cea0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:309 [inline] #9: ffffffff8fd5cea0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline] #9: ffffffff8fd5cea0 (rcu_read_lock){....}-{1:3}, at: ip_finish_output2+0x3de/0x10b0 net/ipv4/ip_output.c:229 #10: ffffffff8fd5cf00 (rcu_read_lock_bh){....}-{1:3}, at: local_bh_disable include/linux/bottom_half.h:20 [inline] #10: ffffffff8fd5cf00 (rcu_read_lock_bh){....}-{1:3}, at: rcu_read_lock_bh include/linux/rcupdate.h:902 [inline] #10: ffffffff8fd5cf00 (rcu_read_lock_bh){....}-{1:3}, at: __dev_queue_xmit+0x29b/0x3920 net/core/dev.c:4872 stack backtrace: CPU: 0 UID: 0 PID: 7143 Comm: dhcpcd-run-hook Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026 Call Trace: 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:4841 [inline] __dev_queue_xmit+0xe9d/0x3920 net/core/dev.c:4952 neigh_output include/net/neighbour.h:560 [inline] ip_finish_output2+0xc4b/0x10b0 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 udp_tunnel_xmit_skb+0x29b/0x3e0 net/ipv4/udp_tunnel_core.c:187 vxlan_xmit_one+0x21f6/0x2eb0 drivers/net/vxlan/vxlan_core.c:2571 vxlan_xmit+0x1e19/0x33b0 drivers/net/vxlan/vxlan_core.c:2860 __netdev_start_xmit include/linux/netdevice.h:5432 [inline] netdev_start_xmit include/linux/netdevice.h:5441 [inline] xmit_one net/core/dev.c:3953 [inline] dev_hard_start_xmit+0x2cd/0x830 net/core/dev.c:3969 __dev_queue_xmit+0x14d1/0x3920 net/core/dev.c:4958 lapb_data_transmit+0x90/0xb0 net/lapb/lapb_iface.c:447 lapb_transmit_buffer+0x163/0x200 net/lapb/lapb_out.c:149 lapb_t1timer_expiry+0x68d/0xaa0 net/lapb/lapb_timer.c:-1 call_timer_fn+0x18d/0x5f0 kernel/time/timer.c:1748 expire_timers kernel/time/timer.c:1799 [inline] __run_timers kernel/time/timer.c:2374 [inline] __run_timer_base+0x652/0x8b0 kernel/time/timer.c:2386 run_timer_base kernel/time/timer.c:2395 [inline] run_timer_softirq+0xb7/0x170 kernel/time/timer.c:2405 handle_softirqs+0x226/0x860 kernel/softirq.c:645 __do_softirq kernel/softirq.c:679 [inline] invoke_softirq kernel/softirq.c:519 [inline] __irq_exit_rcu+0xcb/0x220 kernel/softirq.c:758 irq_exit_rcu+0x9/0x30 kernel/softirq.c:775 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1062 [inline] sysvec_apic_timer_interrupt+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1062 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:674 RIP: 0010:its_return_thunk+0x0/0x10 arch/x86/lib/retpoline.S:437 Code: cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc 90 90 90 90 90 90 90 90 90 90 90 90 90 90 e9 3b 65 39 f5 cc RSP: 0018:ffffc9000f0875d8 EFLAGS: 00000293 RAX: ffffffff82233f2b RBX: ffffea0000525048 RCX: ffff888092408000 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000 RBP: ffffc9000f0878d0 R08: ffffea0000525007 R09: 1ffffd40000a4a00 R10: dffffc0000000000 R11: fffff940000a4a01 R12: 0000000014940000 R13: 00007fa279598000 R14: 0000000000000000 R15: 00007fa279527000 const_folio_flags include/linux/page-flags.h:345 [inline] folio_test_swapbacked include/linux/page-flags.h:572 [inline] mm_counter_file include/linux/mm.h:3489 [inline] mm_counter include/linux/mm.h:3498 [inline] zap_present_folio_ptes mm/memory.c:1789 [inline] zap_present_ptes mm/memory.c:1861 [inline] do_zap_pte_range mm/memory.c:1963 [inline] zap_pte_range mm/memory.c:2065 [inline] zap_pmd_range mm/memory.c:2151 [inline] zap_pud_range mm/memory.c:2179 [inline] zap_p4d_range mm/memory.c:2200 [inline] __zap_vma_range+0x216b/0x4f80 mm/memory.c:2240 unmap_vmas+0x390/0x550 mm/memory.c:2309 exit_mmap+0x293/0x9f0 mm/mmap.c:1315 __mmput+0x118/0x420 kernel/fork.c:1193 exit_mm+0x18e/0x240 kernel/exit.c:592 do_exit+0x6cd/0x2360 kernel/exit.c:974 do_group_exit+0x22d/0x2f0 kernel/exit.c:1129 __do_sys_exit_group kernel/exit.c:1140 [inline] __se_sys_exit_group kernel/exit.c:1138 [inline] __x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1138 x64_sys_call+0x18c6/0x18d0 arch/x86/include/generated/asm/syscalls_64.h:232 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: 0033:0x7fa2794f36c5 Code: Unable to access opcode bytes at 0x7fa2794f369b. RSP: 002b:00007ffd425f5fd8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7 RAX: ffffffffffffffda RBX: 000055b3f7a87910 RCX: 00007fa2794f36c5 RDX: 00000000000000e7 RSI: ffffffffffffff88 RDI: 0000000000000000 RBP: 00007ffd425f6308 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffd425f6300 R13: 00007ffd425f6310 R14: 00007fa279703000 R15: 000055b3df883d98 ---------------- Code disassembly (best guess): 0: cc int3 1: cc int3 2: cc int3 3: cc int3 4: cc int3 5: cc int3 6: cc int3 7: cc int3 8: cc int3 9: cc int3 a: cc int3 b: cc int3 c: cc int3 d: cc int3 e: cc int3 f: cc int3 10: cc int3 11: cc int3 12: cc int3 13: cc int3 14: cc int3 15: cc int3 16: cc int3 17: cc int3 18: cc int3 19: cc int3 1a: cc int3 1b: cc int3 1c: cc int3 1d: cc int3 1e: cc int3 1f: cc int3 20: cc int3 21: cc int3 22: cc int3 23: cc int3 24: cc int3 25: cc int3 26: cc int3 27: cc int3 28: cc int3 29: cc int3 * 2a: c3 ret <-- trapping instruction 2b: cc int3 2c: 90 nop 2d: 90 nop 2e: 90 nop 2f: 90 nop 30: 90 nop 31: 90 nop 32: 90 nop 33: 90 nop 34: 90 nop 35: 90 nop 36: 90 nop 37: 90 nop 38: 90 nop 39: 90 nop 3a: e9 3b 65 39 f5 jmp 0xf539657a 3f: cc int3