=============================
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
5 locks held by syz-executor/4194:
 #0: ffff88814caa4308 (&xt[i].mutex){+.+.}-{3:3}, at: xt_find_table_lock+0x5e/0x360 net/netfilter/x_tables.c:1265
 #1: ffffffff8c31f320 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:313
 #2: ffff88802bb5e148 (dev->qdisc_running_key ?: &qdisc_running_key){+...}-{0:0}, at: net_tx_action+0x6d9/0x880 net/core/dev.c:5154
 #3: ffff88802bb5e108 (&sch->q.lock){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:364 [inline]
 #3: ffff88802bb5e108 (&sch->q.lock){+.-.}-{2:2}, at: sch_direct_xmit+0x311/0x4b0 net/sched/sch_generic.c:357
 #4: ffffffff8c31f320 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:312

stack backtrace:
CPU: 1 PID: 4194 Comm: syz-executor Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
Call Trace:
 <IRQ>
 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:1125
 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
 </IRQ>
 <TASK>
 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:4804
Code: be ff ff ff ff e8 dc 60 68 08 85 c0 74 4a 4d 85 ff 75 66 e9 fe 00 00 00 48 89 df e8 86 cc 71 08 e8 81 e6 2a 00 fb 48 83 c4 08 <5b> 41 5c 41 5d 41 5e 41 5f 5d c3 48 89 df e8 c9 09 fe ff 43 80 3c
RSP: 0018:ffffc90002e8ed28 EFLAGS: 00000286
RAX: 86cd1f4efdd2d400 RBX: ffff8880b903a340 RCX: 86cd1f4efdd2d400
RDX: dffffc0000000000 RSI: ffffffff8a2b3100 RDI: ffffffff8a7a0700
RBP: 1ffff11017227613 R08: ffffffff901d6157 R09: 1ffffffff203ac2a
R10: dffffc0000000000 R11: fffffbfff203ac2b R12: ffff8880b913b088
R13: dffffc0000000000 R14: ffff8880b913ae08 R15: 0000000000000000
 finish_task_switch+0x12f/0x640 kernel/sched/core.c:4921
 context_switch kernel/sched/core.c:5052 [inline]
 __schedule+0x11f7/0x43c0 kernel/sched/core.c:6395
 preempt_schedule_common+0x82/0xd0 kernel/sched/core.c:6571
 preempt_schedule+0xbc/0xd0 kernel/sched/core.c:6596
 preempt_schedule_thunk+0x16/0x18 arch/x86/entry/thunk_64.S:34
 __slab_alloc mm/slub.c:3102 [inline]
 slab_alloc_node mm/slub.c:3191 [inline]
 kmem_cache_alloc_node+0x1e4/0x2d0 mm/slub.c:3261
 alloc_vmap_area+0x1a2/0x1a10 mm/vmalloc.c:1538
 __get_vm_area_node+0x14f/0x2d0 mm/vmalloc.c:2430
 __vmalloc_node_range+0xef/0x8b0 mm/vmalloc.c:3027
 __vmalloc_node mm/vmalloc.c:3087 [inline]
 vzalloc+0x75/0x80 mm/vmalloc.c:3157
 alloc_counters+0xcb/0x750 net/ipv4/netfilter/ip_tables.c:800
 copy_entries_to_user net/ipv4/netfilter/ip_tables.c:822 [inline]
 get_entries net/ipv4/netfilter/ip_tables.c:1023 [inline]
 do_ipt_get_ctl+0xa2f/0x1110 net/ipv4/netfilter/ip_tables.c:1669
 nf_getsockopt+0x25e/0x280 net/netfilter/nf_sockopt.c:116
 ip_getsockopt+0x1256/0x16a0 net/ipv4/ip_sockglue.c:1797
 tcp_getsockopt+0x200/0x25a0 net/ipv4/tcp.c:4322
 __sys_getsockopt+0x1b0/0x230 net/socket.c:2256
 __do_sys_getsockopt net/socket.c:2271 [inline]
 __se_sys_getsockopt net/socket.c:2268 [inline]
 __x64_sys_getsockopt+0xb1/0xc0 net/socket.c:2268
 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: 0033:0x7f51b3edd62a
Code: 48 83 ec 10 89 d2 48 63 ff 45 31 c9 6a 2a 45 31 c0 31 c9 e8 d8 99 fb ff 48 83 c4 18 c3 0f 1f 00 49 89 ca b8 37 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 06 c3 0f 1f 44 00 00 48 c7 c2 e8 ff ff ff f7
RSP: 002b:00007fffc246f378 EFLAGS: 00000216 ORIG_RAX: 0000000000000037
RAX: ffffffffffffffda RBX: 00007fffc246f400 RCX: 00007f51b3edd62a
RDX: 0000000000000041 RSI: 0000000000000000 RDI: 0000000000000003
RBP: 0000000000000003 R08: 00007fffc246f39c R09: 0000000000000000
R10: 00007fffc246f400 R11: 0000000000000216 R12: 00007f51b4129fc0
R13: 00007fffc246f39c R14: 0000000000000000 R15: 00007f51b412c180
 </TASK>
----------------
Code disassembly (best guess):
   0:	be ff ff ff ff       	mov    $0xffffffff,%esi
   5:	e8 dc 60 68 08       	call   0x86860e6
   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 86 cc 71 08       	call   0x871cca6
  20:	e8 81 e6 2a 00       	call   0x2ae6a6
  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 c9 09 fe ff       	call   0xfffe0a06
  3d:	43                   	rex.XB
  3e:	80                   	.byte 0x80
  3f:	3c                   	.byte 0x3c