====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ dhcpcd/15039 is trying to acquire lock: ffff88805738f958 (_xmit_X25#2){+.-.}-{3:3}, at: spin_lock include/linux/spinlock.h:347 [inline] ffff88805738f958 (_xmit_X25#2){+.-.}-{3:3}, at: __netif_tx_lock include/linux/netdevice.h:4841 [inline] ffff88805738f958 (_xmit_X25#2){+.-.}-{3:3}, at: __dev_queue_xmit+0xe9d/0x3920 net/core/dev.c:4952 but task is already holding lock: ffff888054f351c0 (&lapb->lock){+.-.}-{3:3}, at: spin_lock_bh include/linux/spinlock.h:353 [inline] ffff888054f351c0 (&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:1009 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 stack_trace_consume_entry+0xcd/0x280 kernel/stacktrace.c:-1 arch_stack_walk+0x10f/0x150 arch/x86/kernel/stacktrace.c:27 stack_trace_save+0xa9/0x100 kernel/stacktrace.c:122 kasan_save_stack mm/kasan/common.c:57 [inline] kasan_save_track+0x3e/0x80 mm/kasan/common.c:78 poison_kmalloc_redzone mm/kasan/common.c:409 [inline] __kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:426 kasan_kmalloc include/linux/kasan.h:263 [inline] __do_kmalloc_node mm/slub.c:5414 [inline] __kmalloc_noprof+0x36b/0x720 mm/slub.c:5439 _kmalloc_noprof include/linux/slab.h:995 [inline] load_elf_phdrs fs/binfmt_elf.c:537 [inline] load_elf_binary+0x2c6/0x28d0 fs/binfmt_elf.c:866 search_binary_handler fs/exec.c:1779 [inline] exec_binprm fs/exec.c:1811 [inline] bprm_execve+0x930/0x1590 fs/exec.c:1867 do_execveat_common+0x4f4/0x670 fs/exec.c:1965 __do_sys_execve fs/exec.c:2038 [inline] __se_sys_execve fs/exec.c:2032 [inline] __x64_sys_execve+0x97/0xc0 fs/exec.c:2032 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/15039: 9, last CPU#1: #0: ffff88802733ce60 (&sig->cred_guard_mutex){+.+.}-{4:4}, at: prepare_bprm_creds fs/exec.c:1424 [inline] #0: ffff88802733ce60 (&sig->cred_guard_mutex){+.+.}-{4:4}, at: bprm_execve+0xbc/0x1590 fs/exec.c:1847 #1: ffffc90000a08cc0 ((&lapb->t1timer)){+.-.}-{0:0}, at: call_timer_fn+0xd5/0x5f0 kernel/time/timer.c:1745 #2: ffff888054f351c0 (&lapb->lock){+.-.}-{3:3}, at: spin_lock_bh include/linux/spinlock.h:353 [inline] #2: ffff888054f351c0 (&lapb->lock){+.-.}-{3:3}, at: lapb_t1timer_expiry+0x33/0xaa0 net/lapb/lapb_timer.c:99 #3: ffffffff8fd5c980 (rcu_read_lock_bh){....}-{1:3}, at: local_bh_disable include/linux/bottom_half.h:20 [inline] #3: ffffffff8fd5c980 (rcu_read_lock_bh){....}-{1:3}, at: rcu_read_lock_bh include/linux/rcupdate.h:902 [inline] #3: ffffffff8fd5c980 (rcu_read_lock_bh){....}-{1:3}, at: __dev_queue_xmit+0x29b/0x3920 net/core/dev.c:4872 #4: ffffffff8fd5c920 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:309 [inline] #4: ffffffff8fd5c920 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline] #4: ffffffff8fd5c920 (rcu_read_lock){....}-{1:3}, at: vxlan_xmit+0x175d/0x33b0 drivers/net/vxlan/vxlan_core.c:2816 #5: ffffffff8fd5c920 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:309 [inline] #5: ffffffff8fd5c920 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline] #5: ffffffff8fd5c920 (rcu_read_lock){....}-{1:3}, at: vxlan_xmit_one+0x1407/0x2eb0 drivers/net/vxlan/vxlan_core.c:2489 #6: ffffffff8fd5c920 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:309 [inline] #6: ffffffff8fd5c920 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline] #6: ffffffff8fd5c920 (rcu_read_lock){....}-{1:3}, at: ip_output+0x5a/0x450 net/ipv4/ip_output.c:432 #7: ffffffff8fd5c920 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:309 [inline] #7: ffffffff8fd5c920 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline] #7: ffffffff8fd5c920 (rcu_read_lock){....}-{1:3}, at: ip_finish_output2+0x3de/0x10b0 net/ipv4/ip_output.c:229 #8: ffffffff8fd5c980 (rcu_read_lock_bh){....}-{1:3}, at: local_bh_disable include/linux/bottom_half.h:20 [inline] #8: ffffffff8fd5c980 (rcu_read_lock_bh){....}-{1:3}, at: rcu_read_lock_bh include/linux/rcupdate.h:902 [inline] #8: ffffffff8fd5c980 (rcu_read_lock_bh){....}-{1:3}, at: __dev_queue_xmit+0x29b/0x3920 net/core/dev.c:4872 stack backtrace: CPU: 1 UID: 0 PID: 15039 Comm: dhcpcd 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:stack_trace_consume_entry+0xcd/0x280 kernel/stacktrace.c:93 Code: 29 49 89 ff 48 89 74 24 08 49 89 d4 4c 89 04 24 4c 89 cb e8 95 23 86 00 49 89 d9 4c 8b 04 24 4c 89 e2 4c 89 ff 48 8b 74 24 08 <48> 8b 1f 45 8d 79 01 0f b6 44 15 00 84 c0 0f 85 3a 01 00 00 45 89 RSP: 0018:ffffc90011067678 EFLAGS: 00000246 RAX: 1ffff9200220cef0 RBX: ffffc9001106778c RCX: 0000000000000000 RDX: dffffc0000000000 RSI: ffffffff8238c2ee RDI: ffffc90011067780 RBP: 1ffff9200220cef2 R08: ffffc90011067790 R09: 0000000000000000 R10: ffffc90011067718 R11: ffffffff81b2d6c0 R12: 0000000000000000 R13: 1ffff9200220cef1 R14: ffffc90011067788 R15: 1ffff9200220cef1 arch_stack_walk+0x10f/0x150 arch/x86/kernel/stacktrace.c:27 stack_trace_save+0xa9/0x100 kernel/stacktrace.c:122 kasan_save_stack mm/kasan/common.c:57 [inline] kasan_save_track+0x3e/0x80 mm/kasan/common.c:78 poison_kmalloc_redzone mm/kasan/common.c:409 [inline] __kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:426 kasan_kmalloc include/linux/kasan.h:263 [inline] __do_kmalloc_node mm/slub.c:5414 [inline] __kmalloc_noprof+0x36b/0x720 mm/slub.c:5439 _kmalloc_noprof include/linux/slab.h:995 [inline] load_elf_phdrs fs/binfmt_elf.c:537 [inline] load_elf_binary+0x2c6/0x28d0 fs/binfmt_elf.c:866 search_binary_handler fs/exec.c:1779 [inline] exec_binprm fs/exec.c:1811 [inline] bprm_execve+0x930/0x1590 fs/exec.c:1867 do_execveat_common+0x4f4/0x670 fs/exec.c:1965 __do_sys_execve fs/exec.c:2038 [inline] __se_sys_execve fs/exec.c:2032 [inline] __x64_sys_execve+0x97/0xc0 fs/exec.c:2032 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: 0033:0x7f1d0caba107 Code: 0f 00 64 c7 00 07 00 00 00 b8 ff ff ff ff c9 c3 0f 1f 00 48 8b 05 a9 ee 0f 00 48 8b 10 e9 01 00 00 00 90 b8 3b 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d c1 ec 0f 00 f7 d8 64 89 01 48 RSP: 002b:00007f1d0c923e68 EFLAGS: 00000202 ORIG_RAX: 000000000000003b RAX: ffffffffffffffda RBX: 00007ffd6fd71a70 RCX: 00007f1d0caba107 RDX: 00005576c31e98e0 RSI: 00007ffd6fd71c60 RDI: 00005576836746bd RBP: 00007f1d0c923ff0 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000008 R11: 0000000000000202 R12: 0000000000000001 R13: 00007ffd6fd71750 R14: 00007f1d0c923f20 R15: 0000000000000040 ---------------- Code disassembly (best guess), 1 bytes skipped: 0: 49 89 ff mov %rdi,%r15 3: 48 89 74 24 08 mov %rsi,0x8(%rsp) 8: 49 89 d4 mov %rdx,%r12 b: 4c 89 04 24 mov %r8,(%rsp) f: 4c 89 cb mov %r9,%rbx 12: e8 95 23 86 00 call 0x8623ac 17: 49 89 d9 mov %rbx,%r9 1a: 4c 8b 04 24 mov (%rsp),%r8 1e: 4c 89 e2 mov %r12,%rdx 21: 4c 89 ff mov %r15,%rdi 24: 48 8b 74 24 08 mov 0x8(%rsp),%rsi * 29: 48 8b 1f mov (%rdi),%rbx <-- trapping instruction 2c: 45 8d 79 01 lea 0x1(%r9),%r15d 30: 0f b6 44 15 00 movzbl 0x0(%rbp,%rdx,1),%eax 35: 84 c0 test %al,%al 37: 0f 85 3a 01 00 00 jne 0x177 3d: 45 rex.RB 3e: 89 .byte 0x89