=============================
WARNING: suspicious RCU usage
5.15.185-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
4 locks held by syz.3.39/4493:
#0: ffffffff8c11bfa0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:312
#1: ffff88801f19f148 (dev->qdisc_running_key ?: &qdisc_running_key){+...}-{0:0}, at: net_tx_action+0x6bc/0x870 net/core/dev.c:5128
#2: ffff88801f19f108 (&sch->q.lock){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:363 [inline]
#2: ffff88801f19f108 (&sch->q.lock){+.-.}-{2:2}, at: sch_direct_xmit+0x305/0x4a0 net/sched/sch_generic.c:354
#3: ffffffff8c11bfa0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:311
stack backtrace:
CPU: 0 PID: 4493 Comm: syz.3.39 Not tainted 5.15.185-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
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+0x213/0x4e0 net/sched/sch_api.c:800
cake_dequeue+0x1b8f/0x4aa0 net/sched/sch_cake.c:2189
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:292 [inline]
qdisc_restart net/sched/sch_generic.c:397 [inline]
__qdisc_run+0x237/0x1480 net/sched/sch_generic.c:415
qdisc_run+0x103/0x2f0 include/net/pkt_sched.h:132
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:finish_lock_switch+0x134/0x280 kernel/sched/core.c:4785
Code: be ff ff ff ff e8 2c 0e 4e 08 85 c0 74 4a 4d 85 ff 75 66 e9 fe 00 00 00 48 89 df e8 26 6a 57 08 e8 21 7f 2a 00 fb 48 83 c4 08 <5b> 41 5c 41 5d 41 5e 41 5f 5d c3 48 89 df e8 99 10 fe ff 43 80 3c
RSP: 0018:ffffc9000326f968 EFLAGS: 00000282
RAX: 1053cbc33a6c8200 RBX: ffff8880b903a300 RCX: 1053cbc33a6c8200
RDX: dffffc0000000000 RSI: ffffffff8a0b11c0 RDI: ffffffff8a59a740
RBP: 1ffff1101720760b R08: dffffc0000000000 R09: ffffed1017207461
R10: ffffed1017207461 R11: 1ffff11017207460 R12: ffff8880b903b048
R13: dffffc0000000000 R14: ffff8880b903adc8 R15: 0000000000000000
finish_task_switch+0x12f/0x640 kernel/sched/core.c:4902
context_switch kernel/sched/core.c:5033 [inline]
__schedule+0x11c0/0x43b0 kernel/sched/core.c:6376
schedule+0x11b/0x1e0 kernel/sched/core.c:6459
freezable_schedule include/linux/freezer.h:172 [inline]
do_nanosleep+0x1f1/0x760 kernel/time/hrtimer.c:2049
hrtimer_nanosleep+0x2f7/0x520 kernel/time/hrtimer.c:2102
__do_sys_clock_nanosleep kernel/time/posix-timers.c:1314 [inline]
__se_sys_clock_nanosleep+0x2e6/0x370 kernel/time/posix-timers.c:1291
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f8b226711e5
Code: 24 0c 89 3c 24 48 89 4c 24 18 e8 f6 54 ff ff 4c 8b 54 24 18 48 8b 54 24 10 41 89 c0 8b 74 24 0c 8b 3c 24 b8 e6 00 00 00 0f 05 <44> 89 c7 48 89 04 24 e8 4f 55 ff ff 48 8b 04 24 48 83 c4 28 f7 d8
RSP: 002b:00007ffd276b5060 EFLAGS: 00000293 ORIG_RAX: 00000000000000e6
RAX: ffffffffffffffda RBX: 00007f8b22865fa0 RCX: 00007f8b226711e5
RDX: 00007ffd276b50a0 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00007f8b22867ba0 R08: 0000000000000000 R09: 0028ce0560e0d89c
R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000012574
R13: 00007f8b22866080 R14: ffffffffffffffff R15: 00007ffd276b51e0
----------------
Code disassembly (best guess):
0: be ff ff ff ff mov $0xffffffff,%esi
5: e8 2c 0e 4e 08 call 0x84e0e36
a: 85 c0 test %eax,%eax
c: 74 4a je 0x58
e: 4d 85 ff test %r15,%r15
11: 75 66 jne 0x79
13: e9 fe 00 00 00 jmp 0x116
18: 48 89 df mov %rbx,%rdi
1b: e8 26 6a 57 08 call 0x8576a46
20: e8 21 7f 2a 00 call 0x2a7f46
25: fb sti
26: 48 83 c4 08 add $0x8,%rsp
* 2a: 5b pop %rbx <-- trapping instruction
2b: 41 5c pop %r12
2d: 41 5d pop %r13
2f: 41 5e pop %r14
31: 41 5f pop %r15
33: 5d pop %rbp
34: c3 ret
35: 48 89 df mov %rbx,%rdi
38: e8 99 10 fe ff call 0xfffe10d6
3d: 43 rex.XB
3e: 80 .byte 0x80
3f: 3c .byte 0x3c