============================================ WARNING: possible recursive locking detected syzkaller #0 Not tainted -------------------------------------------- swapper/0/0 is trying to acquire lock: ffff88809b526a18 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock#10){+.-.}-{3:3}, at: spin_lock include/linux/spinlock.h:351 [inline] ffff88809b526a18 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock#10){+.-.}-{3:3}, at: __dev_xmit_skb net/core/dev.c:4186 [inline] ffff88809b526a18 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock#10){+.-.}-{3:3}, at: __dev_queue_xmit+0x22b7/0x3b50 net/core/dev.c:4729 but task is already holding lock: ffff88809b526a18 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock#10){+.-.}-{3:3}, at: spin_lock include/linux/spinlock.h:351 [inline] ffff88809b526a18 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock#10){+.-.}-{3:3}, at: __dev_xmit_skb net/core/dev.c:4186 [inline] ffff88809b526a18 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock#10){+.-.}-{3:3}, at: __dev_queue_xmit+0x22b7/0x3b50 net/core/dev.c:4729 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(dev->qdisc_tx_busylock ?: &qdisc_tx_busylock#10); lock(dev->qdisc_tx_busylock ?: &qdisc_tx_busylock#10); *** DEADLOCK *** May be due to missing lock nesting notation 12 locks held by swapper/0/0: #0: ffffc90000007be0 ((&ndev->rs_timer)){+.-.}-{0:0}, at: call_timer_fn+0xbe/0x5f0 kernel/time/timer.c:1744 #1: ffffffff8df3d6e0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline] #1: ffffffff8df3d6e0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:867 [inline] #1: ffffffff8df3d6e0 (rcu_read_lock){....}-{1:3}, at: ndisc_send_skb+0x1e4/0x1510 net/ipv6/ndisc.c:482 #2: ffffffff8df3d6e0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline] #2: ffffffff8df3d6e0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:867 [inline] #2: ffffffff8df3d6e0 (rcu_read_lock){....}-{1:3}, at: ip6_output+0x126/0x550 net/ipv6/ip6_output.c:235 #3: ffffffff8df3d740 (rcu_read_lock_bh){....}-{1:3}, at: local_bh_disable include/linux/bottom_half.h:20 [inline] #3: ffffffff8df3d740 (rcu_read_lock_bh){....}-{1:3}, at: rcu_read_lock_bh include/linux/rcupdate.h:918 [inline] #3: ffffffff8df3d740 (rcu_read_lock_bh){....}-{1:3}, at: __dev_queue_xmit+0x27b/0x3b50 net/core/dev.c:4688 #4: ffffffff8df3d6e0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline] #4: ffffffff8df3d6e0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:867 [inline] #4: ffffffff8df3d6e0 (rcu_read_lock){....}-{1:3}, at: ip6_output+0x126/0x550 net/ipv6/ip6_output.c:235 #5: ffffffff8df3d740 (rcu_read_lock_bh){....}-{1:3}, at: local_bh_disable include/linux/bottom_half.h:20 [inline] #5: ffffffff8df3d740 (rcu_read_lock_bh){....}-{1:3}, at: rcu_read_lock_bh include/linux/rcupdate.h:918 [inline] #5: ffffffff8df3d740 (rcu_read_lock_bh){....}-{1:3}, at: __dev_queue_xmit+0x27b/0x3b50 net/core/dev.c:4688 #6: ffff88809b526a18 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock#10){+.-.}-{3:3}, at: spin_lock include/linux/spinlock.h:351 [inline] #6: ffff88809b526a18 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock#10){+.-.}-{3:3}, at: __dev_xmit_skb net/core/dev.c:4186 [inline] #6: ffff88809b526a18 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock#10){+.-.}-{3:3}, at: __dev_queue_xmit+0x22b7/0x3b50 net/core/dev.c:4729 #7: ffffffff8df3d6e0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline] #7: ffffffff8df3d6e0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:867 [inline] #7: ffffffff8df3d6e0 (rcu_read_lock){....}-{1:3}, at: icmp6_send+0x1e9/0x1940 net/ipv6/icmp.c:478 #8: ffff88802f3481e0 (k-slock-AF_INET6){+.-.}-{3:3}, at: spin_trylock include/linux/spinlock.h:361 [inline] #8: ffff88802f3481e0 (k-slock-AF_INET6){+.-.}-{3:3}, at: icmpv6_xmit_lock net/ipv6/icmp.c:108 [inline] #8: ffff88802f3481e0 (k-slock-AF_INET6){+.-.}-{3:3}, at: icmp6_send+0xc5c/0x1940 net/ipv6/icmp.c:555 #9: ffffffff8df3d6e0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline] #9: ffffffff8df3d6e0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:867 [inline] #9: ffffffff8df3d6e0 (rcu_read_lock){....}-{1:3}, at: ip6_send_skb+0x10f/0x390 net/ipv6/ip6_output.c:1993 #10: ffffffff8df3d6e0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline] #10: ffffffff8df3d6e0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:867 [inline] #10: ffffffff8df3d6e0 (rcu_read_lock){....}-{1:3}, at: ip6_output+0x126/0x550 net/ipv6/ip6_output.c:235 #11: ffffffff8df3d740 (rcu_read_lock_bh){....}-{1:3}, at: local_bh_disable include/linux/bottom_half.h:20 [inline] #11: ffffffff8df3d740 (rcu_read_lock_bh){....}-{1:3}, at: rcu_read_lock_bh include/linux/rcupdate.h:918 [inline] #11: ffffffff8df3d740 (rcu_read_lock_bh){....}-{1:3}, at: __dev_queue_xmit+0x27b/0x3b50 net/core/dev.c:4688 stack backtrace: CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025 Call Trace: dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120 print_deadlock_bug+0x28b/0x2a0 kernel/locking/lockdep.c:3041 check_deadlock kernel/locking/lockdep.c:3093 [inline] validate_chain+0x1a3f/0x2140 kernel/locking/lockdep.c:3895 __lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5237 lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868 __raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline] _raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154 spin_lock include/linux/spinlock.h:351 [inline] __dev_xmit_skb net/core/dev.c:4186 [inline] __dev_queue_xmit+0x22b7/0x3b50 net/core/dev.c:4729 neigh_output include/net/neighbour.h:547 [inline] ip6_finish_output2+0xfb3/0x1480 net/ipv6/ip6_output.c:136 NF_HOOK_COND include/linux/netfilter.h:307 [inline] ip6_output+0x340/0x550 net/ipv6/ip6_output.c:247 ip6_send_skb+0x1d5/0x390 net/ipv6/ip6_output.c:1994 icmp6_send+0x12c6/0x1940 net/ipv6/icmp.c:633 __icmpv6_send include/linux/icmpv6.h:28 [inline] icmpv6_send include/linux/icmpv6.h:49 [inline] ip6_link_failure+0x3b/0x4c0 net/ipv6/route.c:2843 dst_link_failure include/net/dst.h:432 [inline] ipip6_tunnel_xmit net/ipv6/sit.c:1034 [inline] sit_tunnel_xmit+0xaa1/0x1b90 net/ipv6/sit.c:1071 __netdev_start_xmit include/linux/netdevice.h:5248 [inline] netdev_start_xmit include/linux/netdevice.h:5257 [inline] xmit_one net/core/dev.c:3845 [inline] dev_hard_start_xmit+0x2d7/0x830 net/core/dev.c:3861 sch_direct_xmit+0x241/0x4b0 net/sched/sch_generic.c:347 __dev_xmit_skb net/core/dev.c:4202 [inline] __dev_queue_xmit+0x1a47/0x3b50 net/core/dev.c:4729 neigh_output include/net/neighbour.h:547 [inline] ip6_finish_output2+0xfb3/0x1480 net/ipv6/ip6_output.c:136 NF_HOOK_COND include/linux/netfilter.h:307 [inline] ip6_output+0x340/0x550 net/ipv6/ip6_output.c:247 ip6tunnel_xmit+0x1c5/0x3e0 include/net/ip6_tunnel.h:162 ip6_tnl_xmit+0x22d4/0x2b90 net/ipv6/ip6_tunnel.c:1280 __gre6_xmit+0xa47/0xd40 net/ipv6/ip6_gre.c:784 ip6gre_xmit_ipv6 net/ipv6/ip6_gre.c:842 [inline] ip6gre_tunnel_xmit+0xd6e/0x10e0 net/ipv6/ip6_gre.c:894 __netdev_start_xmit include/linux/netdevice.h:5248 [inline] netdev_start_xmit include/linux/netdevice.h:5257 [inline] xmit_one net/core/dev.c:3845 [inline] dev_hard_start_xmit+0x2d7/0x830 net/core/dev.c:3861 __dev_queue_xmit+0x1b8d/0x3b50 net/core/dev.c:4763 neigh_output include/net/neighbour.h:547 [inline] ip6_finish_output2+0xfb3/0x1480 net/ipv6/ip6_output.c:136 NF_HOOK_COND include/linux/netfilter.h:307 [inline] ip6_output+0x340/0x550 net/ipv6/ip6_output.c:247 NF_HOOK include/linux/netfilter.h:318 [inline] ndisc_send_skb+0xbce/0x1510 net/ipv6/ndisc.c:512 addrconf_rs_timer+0x369/0x670 net/ipv6/addrconf.c:4037 call_timer_fn+0x17e/0x5f0 kernel/time/timer.c:1747 expire_timers kernel/time/timer.c:1798 [inline] __run_timers kernel/time/timer.c:2372 [inline] __run_timer_base+0x61a/0x860 kernel/time/timer.c:2384 run_timer_base kernel/time/timer.c:2393 [inline] run_timer_softirq+0xb7/0x180 kernel/time/timer.c:2403 handle_softirqs+0x286/0x870 kernel/softirq.c:622 __do_softirq kernel/softirq.c:656 [inline] invoke_softirq kernel/softirq.c:496 [inline] __irq_exit_rcu+0xca/0x1f0 kernel/softirq.c:723 irq_exit_rcu+0x9/0x30 kernel/softirq.c:739 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1052 [inline] sysvec_apic_timer_interrupt+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1052 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697 RIP: 0010:pv_native_safe_halt+0x13/0x20 arch/x86/kernel/paravirt.c:82 Code: cc cc cc cc cc cc cc 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 66 90 0f 00 2d 93 b1 21 00 f3 0f 1e fa fb f4 c8 e6 02 00 cc cc cc cc cc cc cc cc 90 90 90 90 90 90 90 90 90 RSP: 0018:ffffffff8dc07d80 EFLAGS: 000002c6 RAX: 26c2aecc106c3200 RBX: ffffffff81967b47 RCX: 26c2aecc106c3200 RDX: 0000000000000001 RSI: ffffffff8d70e844 RDI: ffffffff8bbf08e0 RBP: ffffffff8dc07ea8 R08: ffff8880b8832fdb R09: 1ffff110171065fb R10: dffffc0000000000 R11: ffffed10171065fc R12: ffffffff8f7cf270 R13: 0000000000000000 R14: 0000000000000000 R15: 1ffffffff1b92a40 arch_safe_halt arch/x86/include/asm/paravirt.h:107 [inline] default_idle+0x13/0x20 arch/x86/kernel/process.c:767 default_idle_call+0x73/0xb0 kernel/sched/idle.c:122 cpuidle_idle_call kernel/sched/idle.c:190 [inline] do_idle+0x1e7/0x510 kernel/sched/idle.c:330 cpu_startup_entry+0x44/0x60 kernel/sched/idle.c:428 rest_init+0x2de/0x300 init/main.c:757 start_kernel+0x3ae/0x410 init/main.c:1111 x86_64_start_reservations+0x24/0x30 arch/x86/kernel/head64.c:310 x86_64_start_kernel+0x143/0x1c0 arch/x86/kernel/head64.c:291 common_startup_64+0x13e/0x147 ---------------- 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: 90 nop 8: 90 nop 9: 90 nop a: 90 nop b: 90 nop c: 90 nop d: 90 nop e: 90 nop f: 90 nop 10: 90 nop 11: 90 nop 12: 90 nop 13: 90 nop 14: 90 nop 15: 90 nop 16: 90 nop 17: f3 0f 1e fa endbr64 1b: 66 90 xchg %ax,%ax 1d: 0f 00 2d 93 b1 21 00 verw 0x21b193(%rip) # 0x21b1b7 24: f3 0f 1e fa endbr64 28: fb sti 29: f4 hlt * 2a: e9 c8 e6 02 00 jmp 0x2e6f7 <-- trapping instruction 2f: cc int3 30: cc int3 31: cc int3 32: cc int3 33: cc int3 34: cc int3 35: cc int3 36: cc int3 37: 90 nop 38: 90 nop 39: 90 nop 3a: 90 nop 3b: 90 nop 3c: 90 nop 3d: 90 nop 3e: 90 nop 3f: 90 nop