=============================
WARNING: suspicious RCU usage
syzkaller #0 Not tainted
-----------------------------
net/sched/sch_api.c:304 suspicious rcu_dereference_protected() usage!
other info that might help us debug this:
rcu_scheduler_active = 2, debug_locks = 1
8 locks held by kworker/1:18/6572:
#0: ffff888142195538 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: process_one_work+0x760/0x1000 kernel/workqueue.c:-1
#1: ffffc9000414fd00 ((work_completion)(&hub->events)){+.+.}-{0:0}, at: process_one_work+0x7a3/0x1000 kernel/workqueue.c:2285
#2: ffff888023a85220 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:764 [inline]
#2: ffff888023a85220 (&dev->mutex){....}-{3:3}, at: hub_event+0x1a7/0x5560 drivers/usb/core/hub.c:5827
#3: ffffffff8c111260 (console_lock){+.+.}-{0:0}, at: vprintk_emit+0xa7/0x150 kernel/printk/printk.c:2273
#4: ffffffff8c11c720 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:313
#5: ffff888027928948 (dev->qdisc_running_key ?: &qdisc_running_key){+...}-{0:0}, at: net_tx_action+0x6bc/0x870 net/core/dev.c:5128
#6: ffff888027928908 (&sch->q.lock){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:364 [inline]
#6: ffff888027928908 (&sch->q.lock){+.-.}-{2:2}, at: sch_direct_xmit+0x305/0x4a0 net/sched/sch_generic.c:357
#7: ffffffff8c11c720 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:312
stack backtrace:
CPU: 1 PID: 6572 Comm: kworker/1:18 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Workqueue: usb_hub_wq hub_event
Call Trace:
dump_stack_lvl+0x168/0x230 lib/dump_stack.c:106
qdisc_lookup+0xa6/0x650 net/sched/sch_api.c:304
qdisc_tree_reduce_backlog+0x190/0x430 net/sched/sch_api.c:783
cake_dequeue+0x1b8f/0x4aa0 net/sched/sch_cake.c:2199
qdisc_peek_dequeued+0x6e/0x1f0 include/net/sch_generic.h:1115
tbf_dequeue+0x7d/0xce0 net/sched/sch_tbf.c:265
dequeue_skb net/sched/sch_generic.c:295 [inline]
qdisc_restart net/sched/sch_generic.c:400 [inline]
__qdisc_run+0x23f/0x14a0 net/sched/sch_generic.c:418
qdisc_run+0x103/0x2f0 include/net/pkt_sched.h:131
net_tx_action+0x6bc/0x870 net/core/dev.c:5128
handle_softirqs+0x328/0x820 kernel/softirq.c:576
__do_softirq kernel/softirq.c:610 [inline]
invoke_softirq kernel/softirq.c:450 [inline]
__irq_exit_rcu+0x12f/0x220 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+0xa0/0xc0 arch/x86/kernel/apic/apic.c:1108
asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:console_unlock+0xd90/0x1200 kernel/printk/printk.c:2749
Code: 00 48 83 7c 24 28 00 75 19 e8 4c 94 18 00 eb 18 e8 45 94 18 00 e8 80 af 42 08 48 83 7c 24 28 00 74 e7 e8 33 94 18 00 fb 31 ff <89> de e8 89 97 18 00 85 db 0f 94 c0 22 44 24 17 3c 01 75 1f e8 17
RSP: 0018:ffffc9000414f1e0 EFLAGS: 00000246
RAX: ffffffff815f37dd RBX: 0000000000000000 RCX: 0000000000100000
RDX: ffffc90013467000 RSI: 000000000000a0b1 RDI: 0000000000000000
RBP: ffffc9000414f450 R08: dffffc0000000000 R09: fffffbfff1ff5419
R10: fffffbfff1ff5419 R11: 1ffffffff1ff5418 R12: 1ffffffff194c7e9
R13: dffffc0000000000 R14: 0000000000000000 R15: 1ffffffff194c7e2
vprintk_emit+0xc0/0x150 kernel/printk/printk.c:2274
dev_vprintk_emit+0x2cc/0x350 drivers/base/core.c:4638
dev_printk_emit+0xdd/0x120 drivers/base/core.c:4649
_dev_info+0x107/0x150 drivers/base/core.c:4707
announce_device+0xa1/0x2b0 drivers/usb/core/hub.c:2345
usb_new_device+0x4e7/0x1640 drivers/usb/core/hub.c:2613
hub_port_connect drivers/usb/core/hub.c:5497 [inline]
hub_port_connect_change drivers/usb/core/hub.c:5637 [inline]
port_event drivers/usb/core/hub.c:5799 [inline]
hub_event+0x2dd9/0x5560 drivers/usb/core/hub.c:5881
process_one_work+0x863/0x1000 kernel/workqueue.c:2310
worker_thread+0xaa8/0x12a0 kernel/workqueue.c:2457
kthread+0x436/0x520 kernel/kthread.c:334
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
----------------
Code disassembly (best guess):
0: 00 48 83 add %cl,-0x7d(%rax)
3: 7c 24 jl 0x29
5: 28 00 sub %al,(%rax)
7: 75 19 jne 0x22
9: e8 4c 94 18 00 call 0x18945a
e: eb 18 jmp 0x28
10: e8 45 94 18 00 call 0x18945a
15: e8 80 af 42 08 call 0x842af9a
1a: 48 83 7c 24 28 00 cmpq $0x0,0x28(%rsp)
20: 74 e7 je 0x9
22: e8 33 94 18 00 call 0x18945a
27: fb sti
28: 31 ff xor %edi,%edi
* 2a: 89 de mov %ebx,%esi <-- trapping instruction
2c: e8 89 97 18 00 call 0x1897ba
31: 85 db test %ebx,%ebx
33: 0f 94 c0 sete %al
36: 22 44 24 17 and 0x17(%rsp),%al
3a: 3c 01 cmp $0x1,%al
3c: 75 1f jne 0x5d
3e: e8 .byte 0xe8
3f: 17 (bad)