=============================
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
6 locks held by dhcpcd-run-hook/8871:
#0: ffff88807df18128 (&mm->mmap_lock){++++}-{3:3}, at: mmap_read_trylock include/linux/mmap_lock.h:136 [inline]
#0: ffff88807df18128 (&mm->mmap_lock){++++}-{3:3}, at: do_user_addr_fault+0x2b9/0xc80 arch/x86/mm/fault.c:1296
#1: ffff8880732b8678 (ptlock_ptr(page)#2){+.+.}-{2:2}, at: spin_lock include/linux/spinlock.h:364 [inline]
#1: ffff8880732b8678 (ptlock_ptr(page)#2){+.+.}-{2:2}, at: wp_page_copy+0x7ce/0x2050 mm/memory.c:3092
#2: ffffffff8c31eaa0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:313
#3: ffff888027a95148 (dev->qdisc_running_key ?: &qdisc_running_key){+...}-{0:0}, at: net_tx_action+0x6d9/0x880 net/core/dev.c:5154
#4: ffff888027a95108 (&sch->q.lock){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:364 [inline]
#4: ffff888027a95108 (&sch->q.lock){+.-.}-{2:2}, at: sch_direct_xmit+0x311/0x4b0 net/sched/sch_generic.c:357
#5: ffffffff8c31eaa0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:312
stack backtrace:
CPU: 0 PID: 8871 Comm: dhcpcd-run-hook Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
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
cake_dequeue+0x1bd6/0x4b10 net/sched/sch_cake.c:2205
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+0x236/0x1490 net/sched/sch_generic.c:418
qdisc_run+0x103/0x2f0 include/net/pkt_sched.h:131
net_tx_action+0x6d9/0x880 net/core/dev.c:5154
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:flush_tlb_mm_range+0x3f8/0x580 arch/x86/mm/tlb.c:1043
Code: 24 60 41 c6 44 1f 04 f8 fa a9 00 02 00 00 74 05 e8 6d 31 49 00 4c 89 f7 e8 c5 f4 ff ff e8 70 2d 49 00 fb 65 ff 0d e0 55 cc 7e 01 00 00 00 e8 ae 42 1c 00 65 8b 05 4f 50 cc 7e 85 c0 74 37 48
RSP: 0000:ffffc900048efa20 EFLAGS: 00000246
RAX: 9d20b38247164c00 RBX: dffffc0000000000 RCX: 9d20b38247164c00
RDX: dffffc0000000000 RSI: ffffffff8a2b2780 RDI: ffffffff8a79f980
RBP: ffffc900048efaf8 R08: ffffffff901d40c7 R09: 1ffffffff203a818
R10: dffffc0000000000 R11: fffffbfff203a819 R12: ffff8880b9039b26
R13: 1ffff11017207364 R14: ffff8880b9039b00 R15: 1ffff9200091df4c
flush_tlb_page arch/x86/include/asm/tlbflush.h:240 [inline]
ptep_clear_flush+0x112/0x140 mm/pgtable-generic.c:97
wp_page_copy+0xd6b/0x2050 mm/memory.c:3115
handle_pte_fault mm/memory.c:4668 [inline]
__handle_mm_fault mm/memory.c:4785 [inline]
handle_mm_fault+0x1f06/0x4410 mm/memory.c:4883
do_user_addr_fault+0x489/0xc80 arch/x86/mm/fault.c:1355
handle_page_fault arch/x86/mm/fault.c:1443 [inline]
exc_page_fault+0x60/0x100 arch/x86/mm/fault.c:1496
asm_exc_page_fault+0x22/0x30 arch/x86/include/asm/idtentry.h:606
RIP: 0033:0x7fb70604b678
Code: 18 00 00 00 48 8d b8 e0 02 00 00 66 48 0f 6e c7 66 0f 6c c0 0f 11 80 d8 02 00 00 b8 11 01 00 00 0f 05 e8 1b 0e f7 ff 48 89 df 63 e8 f6 ff 48 83 c4 18 89 e8 5b 5d c3 66 2e 0f 1f 84 00 00 00
RSP: 002b:00007fff55947aa0 EFLAGS: 00010202
RAX: 00000000000022a8 RBX: 00007fff55947aa8 RCX: 00007fb70604b636
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00007fff55947aa8
RBP: 00000000000022a8 R08: 0000000000000000 R09: 0000000000000000
R10: 00007fb705eb1f50 R11: 0000000000000246 R12: 00005603fbf43060
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
----------------
Code disassembly (best guess):
0: 24 60 and $0x60,%al
2: 41 c6 44 1f 04 f8 movb $0xf8,0x4(%r15,%rbx,1)
8: fa cli
9: a9 00 02 00 00 test $0x200,%eax
e: 74 05 je 0x15
10: e8 6d 31 49 00 call 0x493182
15: 4c 89 f7 mov %r14,%rdi
18: e8 c5 f4 ff ff call 0xfffff4e2
1d: e8 70 2d 49 00 call 0x492d92
22: fb sti
23: 65 ff 0d e0 55 cc 7e decl %gs:0x7ecc55e0(%rip) # 0x7ecc560a
* 2a: bf 01 00 00 00 mov $0x1,%edi <-- trapping instruction
2f: e8 ae 42 1c 00 call 0x1c42e2
34: 65 8b 05 4f 50 cc 7e mov %gs:0x7ecc504f(%rip),%eax # 0x7ecc508a
3b: 85 c0 test %eax,%eax
3d: 74 37 je 0x76
3f: 48 rex.W