syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P4522/1:b..l
	(detected by 0, t=10502 jiffies, g=7769, q=189)
task:syz.3.64        state:R  running task     stack:25472 pid: 4522 ppid:  4169 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:__sanitizer_cov_trace_pc+0x55/0x60 kernel/kcov.c:214
Code: 2c 8b 91 10 16 00 00 83 fa 02 75 21 48 8b 91 18 16 00 00 48 8b 32 48 8d 7e 01 8b 89 14 16 00 00 48 39 cf 73 08 48 89 44 f2 08 <48> 89 3a c3 0f 1f 80 00 00 00 00 48 8b 04 24 65 48 8b 0d 44 b1 8a
RSP: 0018:ffffc900034ef368 EFLAGS: 00000287
RAX: ffffffff880bfc23 RBX: ffff8880295dcc20 RCX: 0000000000080000
RDX: ffffc90005a7a000 RSI: 000000000004871d RDI: 000000000004871e
RBP: 0000000000000001 R08: ffff8880297f5940 R09: 0000000000000003
R10: 0000000000000003 R11: 0000000000000002 R12: 0000000000000001
R13: ffff8880295dcc18 R14: 0000000000000001 R15: ffffc900034ef420
 nf_hook_slow+0x113/0x200 net/netfilter/core.c:585
 nf_hook+0x1f2/0x350 include/linux/netfilter.h:257
 __ip_local_out+0x4b7/0x5e0 net/ipv4/ip_output.c:115
 ip_local_out net/ipv4/ip_output.c:124 [inline]
 ip_send_skb+0x48/0x1c0 net/ipv4/ip_output.c:1581
 udp_send_skb+0x94a/0x1330 net/ipv4/udp.c:991
 udp_sendmsg+0x19ca/0x2320 net/ipv4/udp.c:1279
 sock_sendmsg_nosec net/socket.c:704 [inline]
 __sock_sendmsg net/socket.c:716 [inline]
 ____sys_sendmsg+0x5a2/0x8c0 net/socket.c:2436
 ___sys_sendmsg+0x1f0/0x260 net/socket.c:2490
 __sys_sendmmsg+0x27c/0x4a0 net/socket.c:2576
 __do_sys_sendmmsg net/socket.c:2605 [inline]
 __se_sys_sendmmsg net/socket.c:2602 [inline]
 __x64_sys_sendmmsg+0x9c/0xb0 net/socket.c:2602
 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: 0033:0x7f4e34f98969
RSP: 002b:00007f4e32e00038 EFLAGS: 00000246 ORIG_RAX: 0000000000000133
RAX: ffffffffffffffda RBX: 00007f4e351bffa0 RCX: 00007f4e34f98969
RDX: 000000000800001d RSI: 0000200000007fc0 RDI: 0000000000000003
RBP: 00007f4e3501aab1 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f4e351bffa0 R15: 00007ffd34c6c4e8
 </TASK>
rcu: rcu_preempt kthread starved for 10405 jiffies! g7769 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=1
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:27464 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 0 to CPUs 1:
NMI backtrace for cpu 1 skipped: idling at native_safe_halt arch/x86/include/asm/irqflags.h:51 [inline]
NMI backtrace for cpu 1 skipped: idling at arch_safe_halt arch/x86/include/asm/irqflags.h:89 [inline]
NMI backtrace for cpu 1 skipped: idling at default_idle+0xb/0x10 arch/x86/kernel/process.c:722