=============================
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
7 locks held by kworker/0:0/7:
#0: ffff888016c72138 ((wq_completion)rcu_gp){+.+.}-{0:0}, at: process_one_work+0x761/0x1010 kernel/workqueue.c:-1
#1: ffffc90000cc7d00 ((work_completion)(&(&ssp->work)->work)){+.+.}-{0:0}, at: process_one_work+0x79f/0x1010 kernel/workqueue.c:2285
#2: ffffc90000007be0 ((&d->timer)){+.-.}-{0:0}, at: lockdep_copy_map include/linux/lockdep.h:45 [inline]
#2: ffffc90000007be0 ((&d->timer)){+.-.}-{0:0}, at: call_timer_fn+0xca/0x540 kernel/time/timer.c:1638
#3: ffffffff8c31eaa0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:312
#4: ffffffff8c31eb00 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:313
#5: ffff888078280908 (&sch->q.lock){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:364 [inline]
#5: ffff888078280908 (&sch->q.lock){+.-.}-{2:2}, at: __dev_xmit_skb net/core/dev.c:3924 [inline]
#5: ffff888078280908 (&sch->q.lock){+.-.}-{2:2}, at: __dev_queue_xmit+0xa2a/0x2f80 net/core/dev.c:4266
#6: ffffffff8c31eaa0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:312
stack backtrace:
CPU: 0 PID: 7 Comm: kworker/0:0 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
Workqueue: rcu_gp process_srcu
Call Trace:
dump_stack_lvl+0x188/0x250 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
fq_codel_enqueue+0x105e/0x1600 net/sched/sch_fq_codel.c:243
cbs_child_enqueue net/sched/sch_cbs.c:95 [inline]
cbs_enqueue_soft+0x1a8/0x270 net/sched/sch_cbs.c:128
dev_qdisc_enqueue+0x48/0x210 net/core/dev.c:3865
__dev_xmit_skb net/core/dev.c:3949 [inline]
__dev_queue_xmit+0xc25/0x2f80 net/core/dev.c:4266
tipc_l2_send_msg+0x30a/0x3c0 net/tipc/bearer.c:518
tipc_bearer_xmit_skb+0x292/0x3c0 net/tipc/bearer.c:577
tipc_disc_timeout+0x57d/0x6d0 net/tipc/discover.c:338
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+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:queue_delayed_work_on+0x1a7/0x1f0 kernel/workqueue.c:1720
Code: 4d 85 ed 75 16 e8 89 1f 2b 00 eb 15 e8 82 1f 2b 00 e8 3d 67 6e 08 4d 85 ed 74 ea e8 73 1f 2b 00 fb 48 c7 44 24 20 0e 36 e0 45 <48> b8 00 00 00 00 00 fc ff df 49 c7 04 06 00 00 00 00 41 c7 44 06
RSP: 0018:ffffc90000cc7b60 EFLAGS: 00000293
RAX: ffffffff814e019d RBX: 0000000000000000 RCX: ffff888016e8bb80
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc90000cc7c30 R08: ffffffff901d40d7 R09: 1ffffffff203a81a
R10: dffffc0000000000 R11: fffffbfff203a81b R12: dffffc0000000001
R13: 0000000000000200 R14: 1ffff92000198f70 R15: 0000000000000000
process_one_work+0x85f/0x1010 kernel/workqueue.c:2310
worker_thread+0xaa6/0x1290 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: 4d 85 ed test %r13,%r13
3: 75 16 jne 0x1b
5: e8 89 1f 2b 00 call 0x2b1f93
a: eb 15 jmp 0x21
c: e8 82 1f 2b 00 call 0x2b1f93
11: e8 3d 67 6e 08 call 0x86e6753
16: 4d 85 ed test %r13,%r13
19: 74 ea je 0x5
1b: e8 73 1f 2b 00 call 0x2b1f93
20: fb sti
21: 48 c7 44 24 20 0e 36 movq $0x45e0360e,0x20(%rsp)
28: e0 45
* 2a: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax <-- trapping instruction
31: fc ff df
34: 49 c7 04 06 00 00 00 movq $0x0,(%r14,%rax,1)
3b: 00
3c: 41 rex.B
3d: c7 .byte 0xc7
3e: 44 06 rex.R (bad)