=============================
WARNING: suspicious RCU usage
6.9.0-rc7-syzkaller-00012-gdccb07f2914c #0 Not tainted
-----------------------------
net/bridge/br_private.h:1599 suspicious rcu_dereference_protected() usage!

other info that might help us debug this:


rcu_scheduler_active = 2, debug_locks = 1
3 locks held by syz-fuzzer/5077:
 #0: ffffffff8e457400 (fill_pool_map-wait-type-override){+.+.}-{3:3}, at: debug_objects_fill_pool lib/debugobjects.c:614 [inline]
 #0: ffffffff8e457400 (fill_pool_map-wait-type-override){+.+.}-{3:3}, at: __debug_object_init+0xbf/0x480 lib/debugobjects.c:627
 #1: ffffc90000a08cb0 ((&p->forward_delay_timer)){+.-.}-{0:0}, at: call_timer_fn+0x11a/0x610 kernel/time/timer.c:1790
 #2: ffff888048ff4cb8 (&br->lock){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:351 [inline]
 #2: ffff888048ff4cb8 (&br->lock){+.-.}-{2:2}, at: br_forward_delay_timer_expired+0x4f/0x560 net/bridge/br_stp_timer.c:86

stack backtrace:
CPU: 1 PID: 5077 Comm: syz-fuzzer Not tainted 6.9.0-rc7-syzkaller-00012-gdccb07f2914c #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
Call Trace:
 <IRQ>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x16c/0x1f0 lib/dump_stack.c:114
 lockdep_rcu_suspicious+0x20b/0x3b0 kernel/locking/lockdep.c:6712
 nbp_vlan_group net/bridge/br_private.h:1599 [inline]
 br_mst_set_state+0x4cd/0x5e0 net/bridge/br_mst.c:105
 br_set_state+0x542/0x880 net/bridge/br_stp.c:47
 br_forward_delay_timer_expired+0x311/0x560 net/bridge/br_stp_timer.c:88
 call_timer_fn+0x1a3/0x610 kernel/time/timer.c:1793
 expire_timers kernel/time/timer.c:1844 [inline]
 __run_timers+0x74b/0xaf0 kernel/time/timer.c:2418
 __run_timer_base kernel/time/timer.c:2429 [inline]
 __run_timer_base kernel/time/timer.c:2422 [inline]
 run_timer_base+0x111/0x190 kernel/time/timer.c:2438
 run_timer_softirq+0x1a/0x40 kernel/time/timer.c:2448
 handle_softirqs+0x219/0x8f0 kernel/softirq.c:554
 __do_softirq kernel/softirq.c:588 [inline]
 invoke_softirq kernel/softirq.c:428 [inline]
 __irq_exit_rcu kernel/softirq.c:637 [inline]
 irq_exit_rcu+0xbb/0x120 kernel/softirq.c:649
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1043 [inline]
 sysvec_apic_timer_interrupt+0x95/0xb0 arch/x86/kernel/apic/apic.c:1043
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702
RIP: 0010:lock_acquire+0x1f2/0x560 kernel/locking/lockdep.c:5722
Code: c1 05 fa 51 95 7e 83 f8 01 0f 85 ea 02 00 00 9c 58 f6 c4 02 0f 85 d5 02 00 00 48 85 ed 74 01 fb 48 b8 00 00 00 00 00 fc ff df <48> 01 c3 48 c7 03 00 00 00 00 48 c7 43 08 00 00 00 00 48 8b 84 24
RSP: 0018:ffffc9000325fb90 EFLAGS: 00000206
RAX: dffffc0000000000 RBX: 1ffff9200064bf74 RCX: 00000000b755b505
RDX: 0000000000000001 RSI: ffffffff8b2cc240 RDI: ffffffff8b8f83e0
RBP: 0000000000000200 R08: 0000000000000000 R09: fffffbfff27ff230
R10: ffffffff93ff9187 R11: 0000000000000000 R12: 0000000000000001
R13: 0000000000000001 R14: ffffffff8e457400 R15: 0000000000000000
 debug_objects_fill_pool lib/debugobjects.c:614 [inline]
 __debug_object_init+0xf2/0x480 lib/debugobjects.c:627
 hrtimer_init_sleeper_on_stack kernel/time/hrtimer.c:448 [inline]
 hrtimer_nanosleep+0x120/0x440 kernel/time/hrtimer.c:2102
 __do_sys_nanosleep kernel/time/hrtimer.c:2139 [inline]
 __se_sys_nanosleep kernel/time/hrtimer.c:2125 [inline]
 __x64_sys_nanosleep+0x21d/0x2b0 kernel/time/hrtimer.c:2125
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcf/0x260 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x472757
Code: 8b 44 24 20 b9 40 42 0f 00 f7 f1 48 89 04 24 b8 e8 03 00 00 f7 e2 48 89 44 24 08 48 89 e7 be 00 00 00 00 b8 23 00 00 00 0f 05 <48> 83 c4 10 5d c3 cc cc cc b8 ba 00 00 00 0f 05 89 44 24 08 c3 cc
RSP: 002b:000000c000069f18 EFLAGS: 00000212 ORIG_RAX: 0000000000000023
RAX: ffffffffffffffda RBX: 00000000000000a0 RCX: 0000000000472757
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 000000c000069f18
RBP: 000000c000069f28 R08: 000000000000655e R09: 0000000000000001
R10: 00007f8af773b080 R11: 0000000000000212 R12: 000000c000069f18
R13: 000000c00043f400 R14: 000000c0000064e0 R15: 0000000000000001
 </TASK>
bridge0: port 1(bridge_slave_0) entered learning state
bridge0: port 2(bridge_slave_1) entered learning state
TCP: request_sock_subflow_v4: Possible SYN flooding on port [::]:20002. Sending cookies.
----------------
Code disassembly (best guess):
   0:	c1 05 fa 51 95 7e 83 	roll   $0x83,0x7e9551fa(%rip)        # 0x7e955201
   7:	f8                   	clc
   8:	01 0f                	add    %ecx,(%rdi)
   a:	85 ea                	test   %ebp,%edx
   c:	02 00                	add    (%rax),%al
   e:	00 9c 58 f6 c4 02 0f 	add    %bl,0xf02c4f6(%rax,%rbx,2)
  15:	85 d5                	test   %edx,%ebp
  17:	02 00                	add    (%rax),%al
  19:	00 48 85             	add    %cl,-0x7b(%rax)
  1c:	ed                   	in     (%dx),%eax
  1d:	74 01                	je     0x20
  1f:	fb                   	sti
  20:	48 b8 00 00 00 00 00 	movabs $0xdffffc0000000000,%rax
  27:	fc ff df
* 2a:	48 01 c3             	add    %rax,%rbx <-- trapping instruction
  2d:	48 c7 03 00 00 00 00 	movq   $0x0,(%rbx)
  34:	48 c7 43 08 00 00 00 	movq   $0x0,0x8(%rbx)
  3b:	00
  3c:	48                   	rex.W
  3d:	8b                   	.byte 0x8b
  3e:	84                   	.byte 0x84
  3f:	24                   	.byte 0x24