=============================
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 modprobe/7084:
 #0: ffff88802a7384f8 (ptlock_ptr(page)
#2){+.+.}-{2:2}, at: spin_lock include/linux/spinlock.h:364 [inline]
#2){+.+.}-{2:2}, at: zap_pte_range mm/memory.c:1342 [inline]
#2){+.+.}-{2:2}, at: zap_pmd_range mm/memory.c:1505 [inline]
#2){+.+.}-{2:2}, at: zap_pud_range mm/memory.c:1534 [inline]
#2){+.+.}-{2:2}, at: zap_p4d_range mm/memory.c:1555 [inline]
#2){+.+.}-{2:2}, at: unmap_page_range+0x94a/0x2500 mm/memory.c:1576
 #1: ffffffff8c31f320 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x0/0x30
 #2: ffffffff8c31f320 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:313
 #3: ffff888078336148 (dev->qdisc_running_key ?: &qdisc_running_key){+...}-{0:0}, at: net_tx_action+0x6d9/0x880 net/core/dev.c:5154
 #4: ffff888078336108 (&sch->q.lock){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:364 [inline]
 #4: ffff888078336108 (&sch->q.lock){+.-.}-{2:2}, at: sch_direct_xmit+0x311/0x4b0 net/sched/sch_generic.c:357
 #5: ffffffff8c31f320 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:312

stack backtrace:
CPU: 0 PID: 7084 Comm: modprobe 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:instrument_atomic_read include/linux/instrumented.h:71 [inline]
RIP: 0010:atomic_read include/linux/atomic/atomic-instrumented.h:27 [inline]
RIP: 0010:lock_page_memcg+0x23d/0x440 mm/memcontrol.c:2062
Code: 00 00 9c 8f 44 24 40 f7 44 24 40 00 02 00 00 c6 44 01 04 f8 0f 85 f9 00 00 00 f7 c3 00 02 00 00 74 01 fb 4d 8d af 80 10 00 00 <4c> 89 ef be 04 00 00 00 e8 36 8f fb ff 4c 89 e8 48 c1 e8 03 48 b9
RSP: 0018:ffffc9000429f760 EFLAGS: 00000206
RAX: dffffc0000000000 RBX: 0000000000000286 RCX: 1ffff92000853ef0
RDX: dffffc0000000000 RSI: ffffffff8a2b3100 RDI: ffffffff8a7a0700
RBP: ffffc9000429f838 R08: ffffffff901d60c7 R09: 1ffffffff203ac18
R10: dffffc0000000000 R11: fffffbfff203ac19 R12: ffff888016e7c670
R13: ffff888016e7d080 R14: ffffea0000284b78 R15: ffff888016e7c000
 page_remove_rmap+0x2a/0x10f0 mm/rmap.c:1351
 zap_pte_range mm/memory.c:1384 [inline]
 zap_pmd_range mm/memory.c:1505 [inline]
 zap_pud_range mm/memory.c:1534 [inline]
 zap_p4d_range mm/memory.c:1555 [inline]
 unmap_page_range+0xf96/0x2500 mm/memory.c:1576
 unmap_vmas+0x131/0x250 mm/memory.c:1653
 exit_mmap+0x3b9/0x640 mm/mmap.c:3216
 __mmput+0x115/0x3b0 kernel/fork.c:1127
 exit_mm+0x5f7/0x770 kernel/exit.c:551
 do_exit+0x5a9/0x20c0 kernel/exit.c:871
 do_group_exit+0x12e/0x300 kernel/exit.c:998
 __do_sys_exit_group kernel/exit.c:1009 [inline]
 __se_sys_exit_group kernel/exit.c:1007 [inline]
 __x64_sys_exit_group+0x3b/0x40 kernel/exit.c:1007
 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: 0033:0x7ffb24fda6c5
Code: Unable to access opcode bytes at RIP 0x7ffb24fda69b.
RSP: 002b:00007ffd44d49e38 EFLAGS: 00000202 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 00007ffb250dbfe8 RCX: 00007ffb24fda6c5
RDX: 00000000000000e7 RSI: ffffffffffffff88 RDI: 0000000000000001
RBP: 0000000000000001 R08: 00007ffd44d49dc8 R09: 0000000000000000
R10: 00007ffd44d49c60 R11: 0000000000000202 R12: 0000000000000000
R13: 0000000000000001 R14: 00007ffb250da680 R15: 00007ffb250dc000
 </TASK>
----------------
Code disassembly (best guess):
   0:	00 00                	add    %al,(%rax)
   2:	9c                   	pushf
   3:	8f 44 24 40          	pop    0x40(%rsp)
   7:	f7 44 24 40 00 02 00 	testl  $0x200,0x40(%rsp)
   e:	00
   f:	c6 44 01 04 f8       	movb   $0xf8,0x4(%rcx,%rax,1)
  14:	0f 85 f9 00 00 00    	jne    0x113
  1a:	f7 c3 00 02 00 00    	test   $0x200,%ebx
  20:	74 01                	je     0x23
  22:	fb                   	sti
  23:	4d 8d af 80 10 00 00 	lea    0x1080(%r15),%r13
* 2a:	4c 89 ef             	mov    %r13,%rdi <-- trapping instruction
  2d:	be 04 00 00 00       	mov    $0x4,%esi
  32:	e8 36 8f fb ff       	call   0xfffb8f6d
  37:	4c 89 e8             	mov    %r13,%rax
  3a:	48 c1 e8 03          	shr    $0x3,%rax
  3e:	48                   	rex.W
  3f:	b9                   	.byte 0xb9