syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
	(detected by 0, t=10506 jiffies, g=18441, q=174)
rcu: All QSes seen, last rcu_preempt kthread activity 10450 (4294965511-4294955061), jiffies_till_next_fqs=1, root ->qsmask 0x0
rcu: rcu_preempt kthread starved for 10450 jiffies! g18441 f0x2 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=0
rcu: 	Unless rcu_preempt kthread gets sufficient CPU time, OOM is now expected behavior.
rcu: RCU grace-period kthread stack dump:
task:rcu_preempt     state:R  running task     stack:27536 pid:   15 ppid:     2 flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5049 [inline]
 __schedule+0x11ef/0x43c0 kernel/sched/core.c:6395
 schedule+0x11b/0x1e0 kernel/sched/core.c:6478
 schedule_timeout+0x184/0x2d0 kernel/time/timer.c:2117
 rcu_gp_fqs_loop+0x2be/0x11d0 kernel/rcu/tree.c:1972
 rcu_gp_kthread+0x9b/0x370 kernel/rcu/tree.c:2145
 kthread+0x436/0x520 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
NMI backtrace for cpu 0
CPU: 0 PID: 7103 Comm: syz.0.733 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Call Trace:
 <IRQ>
 dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106
 nmi_cpu_backtrace+0x3a2/0x3d0 lib/nmi_backtrace.c:111
 nmi_trigger_cpumask_backtrace+0x163/0x280 lib/nmi_backtrace.c:62
 trigger_single_cpu_backtrace include/linux/nmi.h:166 [inline]
 rcu_check_gp_kthread_starvation+0x1cd/0x250 kernel/rcu/tree_stall.h:487
 print_other_cpu_stall+0x1110/0x1270 kernel/rcu/tree_stall.h:592
 check_cpu_stall kernel/rcu/tree_stall.h:745 [inline]
 rcu_pending kernel/rcu/tree.c:3936 [inline]
 rcu_sched_clock_irq+0x843/0x1120 kernel/rcu/tree.c:2619
 update_process_times+0x193/0x200 kernel/time/timer.c:2021
 tick_sched_handle kernel/time/tick-sched.c:254 [inline]
 tick_sched_timer+0x37d/0x560 kernel/time/tick-sched.c:1473
 __run_hrtimer kernel/time/hrtimer.c:1685 [inline]
 __hrtimer_run_queues+0x4ad/0xb70 kernel/time/hrtimer.c:1749
 hrtimer_interrupt+0x3bb/0x8d0 kernel/time/hrtimer.c:1811
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1097 [inline]
 __sysvec_apic_timer_interrupt+0x137/0x4a0 arch/x86/kernel/apic/apic.c:1114
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1108 [inline]
 sysvec_apic_timer_interrupt+0x9b/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:queued_write_lock_slowpath+0x129/0x270 kernel/locking/qrwlock.c:78
Code: f0 41 81 0e 00 01 00 00 43 0f b6 04 27 84 c0 74 37 44 89 f1 80 e1 07 80 c1 03 38 c1 7c 2a 4c 89 f7 e8 2b c5 5f 00 eb 20 f3 90 <43> 0f b6 04 27 84 c0 74 15 44 89 f1 80 e1 07 80 c1 03 38 c1 7c 08
RSP: 0000:ffffc90002dfe9a0 EFLAGS: 00000206
RAX: 00000000000001ff RBX: ffffc90002dfe9f0 RCX: ffffffff815e68bf
RDX: 0000000000000001 RSI: 0000000000000004 RDI: ffffffff8d53ba58
RBP: ffffc90002dfea50 R08: ffffffff8d53ba5b R09: 1ffffffff1aa774b
R10: dffffc0000000000 R11: fffffbfff1aa774c R12: dffffc0000000000
R13: 1ffff920005bfd38 R14: ffffffff8d53ba58 R15: 1ffffffff1aa774b
 queued_write_lock include/asm-generic/qrwlock.h:97 [inline]
 do_raw_write_lock+0x1e6/0x260 kernel/locking/spinlock_debug.c:210
 __neigh_ifdown+0x2c/0x3a0 net/core/neighbour.c:390
 neigh_ifdown+0x1b/0x30 net/core/neighbour.c:408
 rt6_disable_ip+0x616/0x6b0 net/ipv6/route.c:4922
 addrconf_ifdown+0x155/0x19c0 net/ipv6/addrconf.c:3775
 addrconf_notify+0x445/0xf00 net/ipv6/addrconf.c:-1
 notifier_call_chain kernel/notifier.c:83 [inline]
 raw_notifier_call_chain+0xcb/0x160 kernel/notifier.c:391
 call_netdevice_notifiers_extack net/core/dev.c:2074 [inline]
 call_netdevice_notifiers net/core/dev.c:2088 [inline]
 dev_close_many+0x29f/0x400 net/core/dev.c:1663
 unregister_netdevice_many+0x481/0x19f0 net/core/dev.c:11123
 rtnl_delete_link net/core/rtnetlink.c:3114 [inline]
 rtnl_dellink+0x52b/0x7b0 net/core/rtnetlink.c:3165
 rtnetlink_rcv_msg+0x844/0xf30 net/core/rtnetlink.c:5684
 netlink_rcv_skb+0x1f5/0x440 net/netlink/af_netlink.c:2507
 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
 netlink_unicast+0x774/0x920 net/netlink/af_netlink.c:1344
 netlink_sendmsg+0x8ba/0xbe0 net/netlink/af_netlink.c:1918
 sock_sendmsg_nosec net/socket.c:706 [inline]
 __sock_sendmsg net/socket.c:718 [inline]
 ____sys_sendmsg+0x5b7/0x8f0 net/socket.c:2445
 ___sys_sendmsg+0x236/0x2e0 net/socket.c:2499
 __sys_sendmsg net/socket.c:2528 [inline]
 __do_sys_sendmsg net/socket.c:2537 [inline]
 __se_sys_sendmsg+0x1af/0x290 net/socket.c:2535
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f201891ef79
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f2016b79028 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f2018b98fa0 RCX: 00007f201891ef79
RDX: 0000000000000000 RSI: 00002000000000c0 RDI: 0000000000000005
RBP: 00007f20189b57e0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f2018b99038 R14: 00007f2018b98fa0 R15: 00007fffaaa502e8
 </TASK>