============================================ WARNING: possible recursive locking detected syzkaller #0 Not tainted -------------------------------------------- udevd/4294 is trying to acquire lock: ffff88801ea70218 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:364 [inline] ffff88801ea70218 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+.-.}-{2:2}, at: __dev_xmit_skb net/core/dev.c:3922 [inline] ffff88801ea70218 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+.-.}-{2:2}, at: __dev_queue_xmit+0x1fd1/0x2f80 net/core/dev.c:4266 but task is already holding lock: ffff88807d4eb258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+.-.}-{2:2}, at: spin_trylock include/linux/spinlock.h:374 [inline] ffff88807d4eb258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+.-.}-{2:2}, at: qdisc_run_begin include/net/sch_generic.h:173 [inline] ffff88807d4eb258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+.-.}-{2:2}, at: __dev_xmit_skb net/core/dev.c:3884 [inline] ffff88807d4eb258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+.-.}-{2:2}, at: __dev_queue_xmit+0x1120/0x2f80 net/core/dev.c:4266 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(dev->qdisc_tx_busylock ?: &qdisc_tx_busylock); lock(dev->qdisc_tx_busylock ?: &qdisc_tx_busylock); *** DEADLOCK *** May be due to missing lock nesting notation 8 locks held by udevd/4294: #0: ffffc90004737b40 ((&ndev->rs_timer)){+.-.}-{0:0}, at: lockdep_copy_map include/linux/lockdep.h:45 [inline] #0: ffffc90004737b40 ((&ndev->rs_timer)){+.-.}-{0:0}, at: call_timer_fn+0xca/0x540 kernel/time/timer.c:1638 #1: ffffffff8c31f320 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:312 #2: ffffffff8c31f380 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:313 #3: ffffffff8c31f380 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:313 #4: ffff88807d4eb258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+.-.}-{2:2}, at: spin_trylock include/linux/spinlock.h:374 [inline] #4: ffff88807d4eb258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+.-.}-{2:2}, at: qdisc_run_begin include/net/sch_generic.h:173 [inline] #4: ffff88807d4eb258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+.-.}-{2:2}, at: __dev_xmit_skb net/core/dev.c:3884 [inline] #4: ffff88807d4eb258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+.-.}-{2:2}, at: __dev_queue_xmit+0x1120/0x2f80 net/core/dev.c:4266 #5: ffffffff8c31f320 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:313 #6: ffffffff8c31f380 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:313 #7: ffffffff8c31f380 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:313 stack backtrace: CPU: 0 PID: 4294 Comm: udevd Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026 Call Trace: dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106 __lock_acquire+0x1236/0x7d10 kernel/locking/lockdep.c:-1 lock_acquire+0x19e/0x400 kernel/locking/lockdep.c:5623 __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline] _raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:154 spin_lock include/linux/spinlock.h:364 [inline] __dev_xmit_skb net/core/dev.c:3922 [inline] __dev_queue_xmit+0x1fd1/0x2f80 net/core/dev.c:4266 neigh_hh_output include/net/neighbour.h:493 [inline] neigh_output include/net/neighbour.h:507 [inline] ip_finish_output2+0xc87/0x10a0 net/ipv4/ip_output.c:228 NF_HOOK_COND include/linux/netfilter.h:291 [inline] ip_output+0x2c0/0x3e0 net/ipv4/ip_output.c:434 iptunnel_xmit+0x4d6/0x8e0 net/ipv4/ip_tunnel_core.c:82 ip_tunnel_xmit+0x1905/0x2280 net/ipv4/ip_tunnel.c:824 __gre_xmit net/ipv4/ip_gre.c:474 [inline] gre_tap_xmit+0x4f9/0x6e0 net/ipv4/ip_gre.c:751 __netdev_start_xmit include/linux/netdevice.h:5036 [inline] netdev_start_xmit include/linux/netdevice.h:5050 [inline] xmit_one net/core/dev.c:3662 [inline] dev_hard_start_xmit+0x2a5/0x7e0 net/core/dev.c:3678 sch_direct_xmit+0x25a/0x4b0 net/sched/sch_generic.c:345 __dev_xmit_skb net/core/dev.c:3897 [inline] __dev_queue_xmit+0x179f/0x2f80 net/core/dev.c:4266 neigh_hh_output include/net/neighbour.h:493 [inline] neigh_output include/net/neighbour.h:507 [inline] ip6_finish_output2+0x1051/0x1510 net/ipv6/ip6_output.c:130 dst_output include/net/dst.h:452 [inline] NF_HOOK include/linux/netfilter.h:302 [inline] ndisc_send_skb+0xc2a/0x1500 net/ipv6/ndisc.c:513 addrconf_rs_timer+0x2d1/0x630 net/ipv6/addrconf.c:3956 call_timer_fn+0x17b/0x540 kernel/time/timer.c:1648 expire_timers kernel/time/timer.c:1699 [inline] __run_timers+0x53e/0x800 kernel/time/timer.c:1970 run_timer_softirq+0x63/0xf0 kernel/time/timer.c:1983 handle_softirqs+0x339/0x830 kernel/softirq.c:576 __do_softirq kernel/softirq.c:610 [inline] invoke_softirq kernel/softirq.c:450 [inline] __irq_exit_rcu+0x13b/0x230 kernel/softirq.c:659 irq_exit_rcu+0x5/0x20 kernel/softirq.c:671 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1108 [inline] sysvec_apic_timer_interrupt+0x52/0xc0 arch/x86/kernel/apic/apic.c:1108 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676 RIP: 0033:0x7fe71af61097 Code: 73 01 c3 48 8b 0d 61 2d 0d 00 f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 b8 0b 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 31 2d 0d 00 f7 d8 64 89 01 48 RSP: 002b:00007ffe41f96968 EFLAGS: 00000246 RAX: 0000000000000000 RBX: 000055e7295cfdc0 RCX: 00007fe71af61097 RDX: 000055e7295cfda8 RSI: 0000000000000200 RDI: 00007fe71a390000 RBP: 000055e7295e1d10 R08: 000055e7295d36e0 R09: 0000000000000003 R10: 000055e7295e1d00 R11: 0000000000000246 R12: 00007fe71b63e8c0 R13: 00007fe71b64039c R14: 000000000000002e R15: 0000000000000001