=============================
WARNING: suspicious RCU usage
6.9.0-rc7-syzkaller-00137-gc9f9df3f6347 #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-executor.4/12719:
 #0: ffff8880606fc420 (&mm->mmap_lock){++++}-{3:3}, at: mmap_read_lock include/linux/mmap_lock.h:146 [inline]
 #0: ffff8880606fc420 (&mm->mmap_lock){++++}-{3:3}, at: exit_mmap+0x1be/0xd60 mm/mmap.c:3251
 #1: ffffc90000a08be0 ((&p->forward_delay_timer)){+.-.}-{0:0}, at: call_timer_fn+0xc0/0x650 kernel/time/timer.c:1790
 #2: ffff8880247c8cb8 (&br->lock){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:351 [inline]
 #2: ffff8880247c8cb8 (&br->lock){+.-.}-{2:2}, at: br_forward_delay_timer_expired+0x50/0x440 net/bridge/br_stp_timer.c:86

stack backtrace:
CPU: 1 PID: 12719 Comm: syz-executor.4 Not tainted 6.9.0-rc7-syzkaller-00137-gc9f9df3f6347 #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+0x241/0x360 lib/dump_stack.c:114
 lockdep_rcu_suspicious+0x221/0x340 kernel/locking/lockdep.c:6712
 nbp_vlan_group net/bridge/br_private.h:1599 [inline]
 br_mst_set_state+0x1ea/0x650 net/bridge/br_mst.c:105
 br_set_state+0x28a/0x7b0 net/bridge/br_stp.c:47
 br_forward_delay_timer_expired+0x176/0x440 net/bridge/br_stp_timer.c:88
 call_timer_fn+0x18e/0x650 kernel/time/timer.c:1793
 expire_timers kernel/time/timer.c:1844 [inline]
 __run_timers kernel/time/timer.c:2418 [inline]
 __run_timer_base+0x66a/0x8e0 kernel/time/timer.c:2429
 run_timer_base kernel/time/timer.c:2438 [inline]
 run_timer_softirq+0xb7/0x170 kernel/time/timer.c:2448
 handle_softirqs+0x2d6/0x990 kernel/softirq.c:554
 __do_softirq kernel/softirq.c:588 [inline]
 invoke_softirq kernel/softirq.c:428 [inline]
 __irq_exit_rcu+0xf4/0x1c0 kernel/softirq.c:637
 irq_exit_rcu+0x9/0x30 kernel/softirq.c:649
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1043 [inline]
 sysvec_apic_timer_interrupt+0xa6/0xc0 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:folios_put_refs+0x686/0xa60
Code: 8b 6c 24 08 74 08 48 89 df e8 16 1a 29 00 4c 89 33 48 8b 04 24 ff c0 48 89 04 24 49 bc 00 00 00 00 00 fc ff df 4c 8b 74 24 10 <48> 8b 44 24 30 42 0f b6 04 20 84 c0 75 29 41 0f b6 06 49 39 c5 0f
RSP: 0018:ffffc90004daf180 EFLAGS: 00000293
RAX: ffffffff81d19973 RBX: 0000000000000000 RCX: ffff888011cb3c00
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc90004daf290 R08: ffffffff81d19818 R09: 1ffffd40003708b6
R10: dffffc0000000000 R11: fffff940003708b7 R12: dffffc0000000000
R13: 0000000000000003 R14: ffffc90004daf300 R15: ffffc90004daf200
 free_pages_and_swap_cache+0x2ea/0x690 mm/swap_state.c:329
 __tlb_batch_free_encoded_pages mm/mmu_gather.c:136 [inline]
 tlb_batch_pages_flush mm/mmu_gather.c:149 [inline]
 tlb_flush_mmu_free mm/mmu_gather.c:366 [inline]
 tlb_flush_mmu+0x3a3/0x680 mm/mmu_gather.c:373
 zap_pte_range mm/memory.c:1683 [inline]
 zap_pmd_range mm/memory.c:1722 [inline]
 zap_pud_range mm/memory.c:1751 [inline]
 zap_p4d_range mm/memory.c:1772 [inline]
 unmap_page_range+0x3e79/0x4870 mm/memory.c:1793
 unmap_vmas+0x3cc/0x5f0 mm/memory.c:1883
 exit_mmap+0x2cb/0xd60 mm/mmap.c:3267
 __mmput+0x115/0x3c0 kernel/fork.c:1346
 exit_mm+0x220/0x310 kernel/exit.c:569
 do_exit+0x99e/0x27e0 kernel/exit.c:865
 do_group_exit+0x207/0x2c0 kernel/exit.c:1027
 __do_sys_exit_group kernel/exit.c:1038 [inline]
 __se_sys_exit_group kernel/exit.c:1036 [inline]
 __x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1036
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f2e0b47dd69
Code: Unable to access opcode bytes at 0x7f2e0b47dd3f.
RSP: 002b:00007ffc313313b8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 000000000000001e RCX: 00007f2e0b47dd69
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000001 R08: 0000000000000001 R09: 0000000000000000
R10: 00007f2e0b400000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000001 R15: 0000000000000001
 </TASK>
bridge0: port 4(dummy0) entered learning state
----------------
Code disassembly (best guess):
   0:	8b 6c 24 08          	mov    0x8(%rsp),%ebp
   4:	74 08                	je     0xe
   6:	48 89 df             	mov    %rbx,%rdi
   9:	e8 16 1a 29 00       	call   0x291a24
   e:	4c 89 33             	mov    %r14,(%rbx)
  11:	48 8b 04 24          	mov    (%rsp),%rax
  15:	ff c0                	inc    %eax
  17:	48 89 04 24          	mov    %rax,(%rsp)
  1b:	49 bc 00 00 00 00 00 	movabs $0xdffffc0000000000,%r12
  22:	fc ff df
  25:	4c 8b 74 24 10       	mov    0x10(%rsp),%r14
* 2a:	48 8b 44 24 30       	mov    0x30(%rsp),%rax <-- trapping instruction
  2f:	42 0f b6 04 20       	movzbl (%rax,%r12,1),%eax
  34:	84 c0                	test   %al,%al
  36:	75 29                	jne    0x61
  38:	41 0f b6 06          	movzbl (%r14),%eax
  3c:	49 39 c5             	cmp    %rax,%r13
  3f:	0f                   	.byte 0xf