syzbot

============================================
WARNING: possible recursive locking detected
6.2.0-rc3-syzkaller-16369-g358a161a6a9e #0 Not tainted
--------------------------------------------
dhcpcd-run-hook/4558 is trying to acquire lock:
ffff0000c4525338 (&br->multicast_lock){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:350 [inline]
ffff0000c4525338 (&br->multicast_lock){+.-.}-{2:2}, at: br_ip6_multicast_query net/bridge/br_multicast.c:3351 [inline]
ffff0000c4525338 (&br->multicast_lock){+.-.}-{2:2}, at: br_multicast_ipv6_rcv net/bridge/br_multicast.c:3747 [inline]
ffff0000c4525338 (&br->multicast_lock){+.-.}-{2:2}, at: br_multicast_rcv+0x5f4/0x2c38 net/bridge/br_multicast.c:3802

but task is already holding lock:
ffff0000c4527338 (&br->multicast_lock){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:350 [inline]
ffff0000c4527338 (&br->multicast_lock){+.-.}-{2:2}, at: br_multicast_port_query_expired net/bridge/br_multicast.c:1752 [inline]
ffff0000c4527338 (&br->multicast_lock){+.-.}-{2:2}, at: br_ip6_multicast_port_query_expired+0x38/0x160 net/bridge/br_multicast.c:1780

other info that might help us debug this:
 Possible unsafe locking scenario:

       CPU0
       ----
  lock(&br->multicast_lock);
  lock(&br->multicast_lock);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

6 locks held by dhcpcd-run-hook/4558:
 #0: ffff0000c0e74b88 (&mm->mmap_lock){++++}-{3:3}, at: mmap_write_lock_killable include/linux/mmap_lock.h:87 [inline]
 #0: ffff0000c0e74b88 (&mm->mmap_lock){++++}-{3:3}, at: vm_mmap_pgoff+0xa0/0x1d0 mm/util.c:518
 #1: ffff800008003e20 ((&pmctx->ip6_own_query.timer)){+.-.}-{0:0}, at: lockdep_copy_map include/linux/lockdep.h:31 [inline]
 #1: ffff800008003e20 ((&pmctx->ip6_own_query.timer)){+.-.}-{0:0}, at: call_timer_fn+0x54/0x144 kernel/time/timer.c:1690
 #2: ffff0000c4527338 (&br->multicast_lock){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:350 [inline]
 #2: ffff0000c4527338 (&br->multicast_lock){+.-.}-{2:2}, at: br_multicast_port_query_expired net/bridge/br_multicast.c:1752 [inline]
 #2: ffff0000c4527338 (&br->multicast_lock){+.-.}-{2:2}, at: br_ip6_multicast_port_query_expired+0x38/0x160 net/bridge/br_multicast.c:1780
 #3: ffff80000d645548 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x18/0x54 include/linux/rcupdate.h:324
 #4: ffff80000d645548 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x18/0x54 include/linux/rcupdate.h:324
 #5: ffff80000d645520 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x10/0x4c include/linux/rcupdate.h:324

stack backtrace:
CPU: 0 PID: 4558 Comm: dhcpcd-run-hook Not tainted 6.2.0-rc3-syzkaller-16369-g358a161a6a9e #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022
Call trace:
 dump_backtrace+0x1c4/0x1f0 arch/arm64/kernel/stacktrace.c:156
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:163
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x104/0x16c lib/dump_stack.c:106
 dump_stack+0x1c/0x58 lib/dump_stack.c:113
 __lock_acquire+0x808/0x3084
 lock_acquire+0x100/0x1f8 kernel/locking/lockdep.c:5668
 __raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
 _raw_spin_lock+0x54/0x6c kernel/locking/spinlock.c:154
 spin_lock include/linux/spinlock.h:350 [inline]
 br_ip6_multicast_query net/bridge/br_multicast.c:3351 [inline]
 br_multicast_ipv6_rcv net/bridge/br_multicast.c:3747 [inline]
 br_multicast_rcv+0x5f4/0x2c38 net/bridge/br_multicast.c:3802
 br_dev_xmit+0x4ac/0x924 net/bridge/br_device.c:89
 __netdev_start_xmit include/linux/netdevice.h:4865 [inline]
 netdev_start_xmit include/linux/netdevice.h:4879 [inline]
 xmit_one net/core/dev.c:3583 [inline]
 dev_hard_start_xmit+0xd4/0x1ec net/core/dev.c:3599
 __dev_queue_xmit+0x83c/0xdb8 net/core/dev.c:4249
 dev_queue_xmit include/linux/netdevice.h:3035 [inline]
 vlan_dev_hard_start_xmit+0x110/0x260 net/8021q/vlan_dev.c:124
 __netdev_start_xmit include/linux/netdevice.h:4865 [inline]
 netdev_start_xmit include/linux/netdevice.h:4879 [inline]
 xmit_one net/core/dev.c:3583 [inline]
 dev_hard_start_xmit+0xd4/0x1ec net/core/dev.c:3599
 __dev_queue_xmit+0x83c/0xdb8 net/core/dev.c:4249
 dev_queue_xmit include/linux/netdevice.h:3035 [inline]
 br_dev_queue_push_xmit+0x318/0x388 net/bridge/br_forward.c:53
 NF_HOOK include/linux/netfilter.h:302 [inline]
 __br_multicast_send_query+0xf60/0x11d0 net/bridge/br_multicast.c:1656
 br_multicast_send_query+0x254/0x298 net/bridge/br_multicast.c:1735
 br_multicast_port_query_expired net/bridge/br_multicast.c:1760 [inline]
 br_ip6_multicast_port_query_expired+0x140/0x160 net/bridge/br_multicast.c:1780
 call_timer_fn+0x90/0x144 kernel/time/timer.c:1700
 expire_timers kernel/time/timer.c:1751 [inline]
 __run_timers+0x284/0x384 kernel/time/timer.c:2022
 run_timer_softirq+0x34/0x5c kernel/time/timer.c:2035
 _stext+0x168/0x37c
 ____do_softirq+0x14/0x20 arch/arm64/kernel/irq.c:80
 call_on_irq_stack+0x2c/0x54 arch/arm64/kernel/entry.S:892
 do_softirq_own_stack+0x20/0x2c arch/arm64/kernel/irq.c:85
 invoke_softirq+0x70/0xbc kernel/softirq.c:452
 __irq_exit_rcu+0xf0/0x140 kernel/softirq.c:650
 irq_exit_rcu+0x10/0x40 kernel/softirq.c:662
 __el1_irq arch/arm64/kernel/entry-common.c:472 [inline]
 el1_interrupt+0x38/0x68 arch/arm64/kernel/entry-common.c:486
 el1h_64_irq_handler+0x18/0x24 arch/arm64/kernel/entry-common.c:491
 el1h_64_irq+0x64/0x68 arch/arm64/kernel/entry.S:580
 arch_local_irq_restore arch/arm64/include/asm/irqflags.h:122 [inline]
 put_cpu_partial+0x164/0x1b4 mm/slub.c:2710
 __slab_free+0x184/0x250 mm/slub.c:3653
 do_slab_free mm/slub.c:3731 [inline]
 slab_free mm/slub.c:3788 [inline]
 kmem_cache_free+0x2a8/0x3a4 mm/slub.c:3809
 vm_area_free+0x38/0xe8 kernel/fork.c:485
 remove_vma mm/mmap.c:144 [inline]
 remove_mt mm/mmap.c:2163 [inline]
 do_mas_align_munmap+0x710/0x894 mm/mmap.c:2443
 do_mas_munmap mm/mmap.c:2498 [inline]
 mmap_region+0x434/0x1064 mm/mmap.c:2546
 do_mmap+0x6e0/0xa28 mm/mmap.c:1411
 vm_mmap_pgoff+0xe8/0x1d0 mm/util.c:520
 ksys_mmap_pgoff+0xa0/0x278 mm/mmap.c:1457
 __do_sys_mmap arch/arm64/kernel/sys.c:28 [inline]
 __se_sys_mmap arch/arm64/kernel/sys.c:21 [inline]
 __arm64_sys_mmap+0x58/0x6c arch/arm64/kernel/sys.c:21
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall arch/arm64/kernel/syscall.c:52 [inline]
 el0_svc_common+0x138/0x220 arch/arm64/kernel/syscall.c:142
 do_el0_svc+0x48/0x140 arch/arm64/kernel/syscall.c:197
 el0_svc+0x58/0x150 arch/arm64/kernel/entry-common.c:637
 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
 el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:584