syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P5836/1:b..l
	(detected by 1, t=10502 jiffies, g=23977, q=151 ncpus=2)
task:dhcpcd-run-hook state:R  running task     stack:24352 pid:5836  ppid:3932   flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5244 [inline]
 __schedule+0x10ec/0x40b0 kernel/sched/core.c:6561
 preempt_schedule_irq+0xb1/0x150 kernel/sched/core.c:6873
 irqentry_exit+0x63/0x70 kernel/entry/common.c:439
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:691
RIP: 0010:__sanitizer_cov_trace_pc+0x0/0x60 kernel/kcov.c:212
Code: 2e 0f 1f 84 00 00 00 00 00 90 53 48 89 fb e8 17 00 00 00 48 8b 3d 40 a3 9e 0c 48 89 de 5b e9 57 53 4f 00 00 00 cc cc 00 00 cc <48> 8b 04 24 65 48 8b 0d 14 9f 81 7e 65 8b 15 15 9f 81 7e 81 e2 00
RSP: 0018:ffffc900036bf678 EFLAGS: 00000286
RAX: 0000000000000080 RBX: ffffffff8bb161c8 RCX: ffff88807b3e1dc0
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000003
RBP: ffffc900036bf850 R08: ffff88807b3e1dc0 R09: 0000000000000003
R10: 0000000000000003 R11: 0000000000000000 R12: dffffc0000000000
R13: ffff888061bd5480 R14: ffff8880287db600 R15: 0000000000000000
 mt_validate_nulls lib/maple_tree.c:7209 [inline]
 mt_validate+0x42e9/0x4c90 lib/maple_tree.c:7247
 validate_mm_mt+0xcd/0x420 mm/mmap.c:295
 validate_mm+0xcc/0x2b0 mm/mmap.c:332
 mmap_region+0x780/0x1c70 mm/mmap.c:2922
 do_mmap+0x958/0xfd0 mm/mmap.c:1436
 vm_mmap_pgoff+0x1b2/0x2b0 mm/util.c:520
 ksys_mmap_pgoff+0x516/0x6f0 mm/mmap.c:1482
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f0f16ea5242
RSP: 002b:00007ffc9b3b4fc8 EFLAGS: 00000206 ORIG_RAX: 0000000000000009
RAX: ffffffffffffffda RBX: 00007f0f16b7f000 RCX: 00007f0f16ea5242
RDX: 0000000000000001 RSI: 0000000000002000 RDI: 00007f0f16b7f000
RBP: 0000000000000812 R08: 0000000000000003 R09: 0000000000005000
R10: 0000000000000812 R11: 0000000000000206 R12: 00007ffc9b3b5050
R13: 00007f0f16b840c0 R14: 00007ffc9b3b5400 R15: 00000fff936769fc
 </TASK>
rcu: rcu_preempt kthread starved for 10529 jiffies! g23977 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:27512 pid:16    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5244 [inline]
 __schedule+0x10ec/0x40b0 kernel/sched/core.c:6561
 schedule+0xb9/0x180 kernel/sched/core.c:6637
 schedule_timeout+0x15c/0x280 kernel/time/timer.c:1965
 rcu_gp_fqs_loop+0x2f2/0x1310 kernel/rcu/tree.c:1706
 rcu_gp_kthread+0x95/0x380 kernel/rcu/tree.c:1905
 kthread+0x29d/0x330 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
 </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:741