=============================
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.3.1342/9697:
 #0: ffffffff8c11bfa0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:312
 #1: ffff88807ae5c948 (dev->qdisc_running_key ?: &qdisc_running_key){+...}-{0:0}, at: net_tx_action+0x6bc/0x870 net/core/dev.c:5128
 #2: ffff88807ae5c908 (&sch->q.lock){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:363 [inline]
 #2: ffff88807ae5c908 (&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: 1 PID: 9697 Comm: syz.3.1342 Not tainted 5.15.185-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Call Trace:
 <IRQ>
 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
 codel_qdisc_dequeue+0x1523/0x2100 net/sched/sch_codel.c:102
 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
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:unwind_next_frame+0x75/0x1d90 arch/x86/kernel/unwind_orc.c:425
Code: 03 48 89 44 24 40 42 80 3c 30 00 74 08 4c 89 ff e8 70 d1 88 00 4c 89 7c 24 38 4c 8b 6b 38 49 89 df 49 c1 ef 03 43 0f b6 04 37 <84> c0 0f 85 b7 16 00 00 8b 03 85 c0 0f 84 f1 14 00 00 48 89 6c 24
RSP: 0018:ffffc9000366eda8 EFLAGS: 00000a02
RAX: 0000000000000000 RBX: ffffc9000366ee68 RCX: 0000000080000001
RDX: dffffc0000000000 RSI: ffffffff81cd4ba1 RDI: ffffc9000366ee68
RBP: ffffc9000366eeb0 R08: ffffc9000366ef30 R09: 0000000000000007
R10: fffff520006cddd9 R11: 1ffff920006cddd7 R12: ffffffff81cd4ba1
R13: ffffc9000366f8e0 R14: dffffc0000000000 R15: 1ffff920006cddcd
 arch_stack_walk+0x10c/0x140 arch/x86/kernel/stacktrace.c:25
 stack_trace_save+0x98/0xe0 kernel/stacktrace.c:122
 save_stack+0xf3/0x1e0 mm/page_owner.c:119
 __reset_page_owner+0x51/0x180 mm/page_owner.c:140
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1340 [inline]
 free_pcp_prepare mm/page_alloc.c:1391 [inline]
 free_unref_page_prepare+0x637/0x6c0 mm/page_alloc.c:3317
 free_unref_page_list+0x122/0x7e0 mm/page_alloc.c:3433
 release_pages+0x184b/0x1bb0 mm/swap.c:963
 __pagevec_release+0x6d/0xe0 mm/swap.c:983
 pagevec_release include/linux/pagevec.h:81 [inline]
 shmem_undo_range+0x593/0x1840 mm/shmem.c:964
 shmem_truncate_range mm/shmem.c:1063 [inline]
 shmem_evict_inode+0x20d/0xa00 mm/shmem.c:1145
 evict+0x485/0x870 fs/inode.c:647
 __dentry_kill+0x431/0x650 fs/dcache.c:586
 dentry_kill+0xb8/0x290 fs/dcache.c:-1
 dput+0xd8/0x1a0 fs/dcache.c:893
 __fput+0x5ee/0x930 fs/file_table.c:319
 task_work_run+0x125/0x1a0 kernel/task_work.c:188
 exit_task_work include/linux/task_work.h:33 [inline]
 do_exit+0x616/0x20a0 kernel/exit.c:874
 do_group_exit+0x12e/0x300 kernel/exit.c:996
 get_signal+0x6ca/0x12c0 kernel/signal.c:2900
 arch_do_signal_or_restart+0xc1/0x1300 arch/x86/kernel/signal.c:867
 handle_signal_work kernel/entry/common.c:154 [inline]
 exit_to_user_mode_loop+0x9e/0x130 kernel/entry/common.c:178
 exit_to_user_mode_prepare+0xb1/0x140 kernel/entry/common.c:214
 __syscall_exit_to_user_mode_work kernel/entry/common.c:296 [inline]
 syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:307
 do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f65360b9929
Code: Unable to access opcode bytes at RIP 0x7f65360b98ff.
RSP: 002b:00007f6533edf038 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
RAX: fffffffffffffff7 RBX: 00007f65362e1160 RCX: 00007f65360b9929
RDX: 0000000000000050 RSI: 0000200000001040 RDI: 0000000000000000
RBP: 00007f653613bb39 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f65362e1160 R15: 00007fffcd8c0168
 </TASK>
----------------
Code disassembly (best guess):
   0:	03 48 89             	add    -0x77(%rax),%ecx
   3:	44 24 40             	rex.R and $0x40,%al
   6:	42 80 3c 30 00       	cmpb   $0x0,(%rax,%r14,1)
   b:	74 08                	je     0x15
   d:	4c 89 ff             	mov    %r15,%rdi
  10:	e8 70 d1 88 00       	call   0x88d185
  15:	4c 89 7c 24 38       	mov    %r15,0x38(%rsp)
  1a:	4c 8b 6b 38          	mov    0x38(%rbx),%r13
  1e:	49 89 df             	mov    %rbx,%r15
  21:	49 c1 ef 03          	shr    $0x3,%r15
  25:	43 0f b6 04 37       	movzbl (%r15,%r14,1),%eax
* 2a:	84 c0                	test   %al,%al <-- trapping instruction
  2c:	0f 85 b7 16 00 00    	jne    0x16e9
  32:	8b 03                	mov    (%rbx),%eax
  34:	85 c0                	test   %eax,%eax
  36:	0f 84 f1 14 00 00    	je     0x152d
  3c:	48                   	rex.W
  3d:	89                   	.byte 0x89
  3e:	6c                   	insb   (%dx),%es:(%rdi)
  3f:	24                   	.byte 0x24