=============================
WARNING: suspicious RCU usage
6.9.0-syzkaller #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
2 locks held by syz-fuzzer/5076:
 #0: ffffc90000007cb0 ((&p->forward_delay_timer)){+.-.}-{0:0}, at: call_timer_fn+0x11a/0x610 kernel/time/timer.c:1790
 #1: ffff8880781d4cb8 (&br->lock){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:351 [inline]
 #1: ffff8880781d4cb8 (&br->lock){+.-.}-{2:2}, at: br_forward_delay_timer_expired+0x4f/0x560 net/bridge/br_stp_timer.c:86

stack backtrace:
CPU: 0 PID: 5076 Comm: syz-fuzzer Not tainted 6.9.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/02/2024
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:finish_task_switch.isra.0+0x220/0xcc0 kernel/sched/core.c:5283
Code: a9 0a 00 00 44 8b 0d d7 b7 60 0e 45 85 c9 0f 85 c0 01 00 00 48 89 df e8 ae f8 ff ff e8 89 81 36 00 fb 65 48 8b 1d 60 31 a4 7e <48> 8d bb f0 15 00 00 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1
RSP: 0018:ffffc90004797a98 EFLAGS: 00000206
RAX: 0000000000bfce99 RBX: ffff88802572da00 RCX: 1ffffffff1f7fcf9
RDX: 0000000000000000 RSI: ffffffff8b2cbf20 RDI: ffffffff8b8f8520
RBP: ffffc90004797ae0 R08: 0000000000000001 R09: 0000000000000001
R10: ffffffff8fc02a57 R11: 0000000000000000 R12: ffff8880b943f7f8
R13: ffff888028ef8000 R14: 0000000000000000 R15: ffff8880b943ea80
 context_switch kernel/sched/core.c:5412 [inline]
 __schedule+0xf1d/0x5d00 kernel/sched/core.c:6746
 __schedule_loop kernel/sched/core.c:6823 [inline]
 schedule+0xe7/0x350 kernel/sched/core.c:6838
 do_nanosleep+0x216/0x510 kernel/time/hrtimer.c:2051
 hrtimer_nanosleep+0x1ab/0x440 kernel/time/hrtimer.c:2104
 __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: 0033:0x472f57
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:000000c00006bf18 EFLAGS: 00000212 ORIG_RAX: 0000000000000023
RAX: ffffffffffffffda RBX: 0000000000000014 RCX: 0000000000472f57
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 000000c00006bf18
RBP: 000000c00006bf28 R08: 0000000000004910 R09: 0000000000000001
R10: 00007f41de0d0080 R11: 0000000000000212 R12: 000000c00006bf18
R13: 000000c000302800 R14: 000000c0000064e0 R15: 0000000000000013
 </TASK>
bridge0: port 3(erspan0) entered learning state
----------------
Code disassembly (best guess):
   0:	a9 0a 00 00 44       	test   $0x4400000a,%eax
   5:	8b 0d d7 b7 60 0e    	mov    0xe60b7d7(%rip),%ecx        # 0xe60b7e2
   b:	45 85 c9             	test   %r9d,%r9d
   e:	0f 85 c0 01 00 00    	jne    0x1d4
  14:	48 89 df             	mov    %rbx,%rdi
  17:	e8 ae f8 ff ff       	call   0xfffff8ca
  1c:	e8 89 81 36 00       	call   0x3681aa
  21:	fb                   	sti
  22:	65 48 8b 1d 60 31 a4 	mov    %gs:0x7ea43160(%rip),%rbx        # 0x7ea4318a
  29:	7e
* 2a:	48 8d bb f0 15 00 00 	lea    0x15f0(%rbx),%rdi <-- trapping instruction
  31:	48 b8 00 00 00 00 00 	movabs $0xdffffc0000000000,%rax
  38:	fc ff df
  3b:	48 89 fa             	mov    %rdi,%rdx
  3e:	48                   	rex.W
  3f:	c1                   	.byte 0xc1