syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P4173/1:b..l P13/1:b..l
	(detected by 1, t=10502 jiffies, g=7105, q=201)
task:kworker/0:1     state:R  running task     stack:24104 pid:   13 ppid:     2 flags:0x00004000
Workqueue: ipv6_addrconf addrconf_dad_work
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5030 [inline]
 __schedule+0x11b8/0x43b0 kernel/sched/core.c:6376
 preempt_schedule_common+0x82/0xd0 kernel/sched/core.c:6552
 preempt_schedule+0xa7/0xb0 kernel/sched/core.c:6577
 preempt_schedule_thunk+0x16/0x18 arch/x86/entry/thunk_64.S:34
 __local_bh_enable_ip+0x13b/0x1b0 kernel/softirq.c:390
 rcu_read_unlock_bh include/linux/rcupdate.h:809 [inline]
 ip6_finish_output2+0x110b/0x1500 net/ipv6/ip6_output.c:131
 dst_output include/net/dst.h:452 [inline]
 NF_HOOK include/linux/netfilter.h:302 [inline]
 ndisc_send_skb+0xbea/0x14a0 net/ipv6/ndisc.c:513
 addrconf_dad_completed+0x798/0xca0 net/ipv6/addrconf.c:4278
 addrconf_dad_work+0xc70/0x1520 net/ipv6/addrconf.c:-1
 process_one_work+0x863/0x1000 kernel/workqueue.c:2310
 worker_thread+0xaa8/0x12a0 kernel/workqueue.c:2457
 kthread+0x436/0x520 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </TASK>
task:syz-executor    state:R  running task     stack:21632 pid: 4173 ppid:  4166 flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5030 [inline]
 __schedule+0x11b8/0x43b0 kernel/sched/core.c:6376
 preempt_schedule_irq+0xb1/0x150 kernel/sched/core.c:6780
 irqentry_exit+0x63/0x70 kernel/entry/common.c:432
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:__preempt_count_add kernel/rcu/tree.c:1119 [inline]
RIP: 0010:rcu_is_watching+0x4/0xa0 kernel/rcu/tree.c:1122
Code: 8d 65 e8 5b 41 5e 41 5f 5d c3 e8 87 94 3d 08 41 f7 c7 00 02 00 00 75 b8 eb b7 e8 67 94 3d 08 0f 1f 80 00 00 00 00 41 57 41 56 <53> 65 ff 05 1c d7 9e 7e e8 5f a4 3d 08 89 c3 83 f8 08 73 5c 49 bf
RSP: 0018:ffffc90002f0faf8 EFLAGS: 00000202
RAX: 0000000000000001 RBX: ffff8880257dbbac RCX: ffff8880257dbb80
RDX: 0000000000000000 RSI: ffffffff8a0b2260 RDI: ffffffff8a59a2c0
RBP: 0000000000400cc0 R08: dffffc0000000000 R09: fffffbfff1ff3219
R10: fffffbfff1ff3219 R11: 1ffffffff1ff3218 R12: ffff888024f7baa0
R13: ffff88802bec1f24 R14: ffff8880257dc090 R15: dffffc0000000000
 rcu_read_lock include/linux/rcupdate.h:740 [inline]
 get_obj_cgroup_from_current+0xdf/0x2f0 mm/memcontrol.c:2924
 memcg_slab_pre_alloc_hook mm/slab.h:283 [inline]
 slab_pre_alloc_hook+0x7e/0xc0 mm/slab.h:497
 slab_alloc_node mm/slub.c:3134 [inline]
 slab_alloc mm/slub.c:3228 [inline]
 __kmalloc_track_caller+0x69/0x330 mm/slub.c:4925
 kstrdup mm/util.c:60 [inline]
 kstrdup_const+0x51/0x90 mm/util.c:83
 alloc_vfsmnt+0x9d/0x450 fs/namespace.c:207
 clone_mnt+0x6b/0xce0 fs/namespace.c:1061
 copy_tree+0x3d4/0x7e0 fs/namespace.c:1879
 __do_loopback+0x193/0x330 fs/namespace.c:2363
 do_loopback+0x387/0x4f0 fs/namespace.c:2403
 do_mount fs/namespace.c:3356 [inline]
 __do_sys_mount fs/namespace.c:3564 [inline]
 __se_sys_mount+0x2d6/0x3c0 fs/namespace.c:3541
 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: 0033:0x7fbc35ede10a
RSP: 002b:00007ffcc2f13c58 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007fbc35f5ee89 RCX: 00007fbc35ede10a
RDX: 0000000000000000 RSI: 00007fbc35f5ef96 RDI: 00007fbc35f5efa7
RBP: 00007fbc35f5ef96 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000045000 R11: 0000000000000246 R12: 000055558041f4a8
R13: 0000000000000003 R14: 0000000000000009 R15: 0000000000000000
 </TASK>
rcu: rcu_preempt kthread starved for 10556 jiffies! g7105 f0x0 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:28032 pid:   15 ppid:     2 flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5030 [inline]
 __schedule+0x11b8/0x43b0 kernel/sched/core.c:6376
 schedule+0x11b/0x1e0 kernel/sched/core.c:6459
 schedule_timeout+0x15c/0x280 kernel/time/timer.c:1914
 rcu_gp_fqs_loop+0x29e/0x11b0 kernel/rcu/tree.c:1972
 rcu_gp_kthread+0x98/0x350 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:
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0 skipped: idling at native_safe_halt arch/x86/include/asm/irqflags.h:51 [inline]
NMI backtrace for cpu 0 skipped: idling at arch_safe_halt arch/x86/include/asm/irqflags.h:89 [inline]
NMI backtrace for cpu 0 skipped: idling at default_idle+0xb/0x10 arch/x86/kernel/process.c:722