syzbot

rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 	1-...!: (10499 ticks this GP) idle=c96/1/0x4000000000000002 softirq=12095/12095 fqs=5 
	(t=10500 jiffies g=6397 q=248)
rcu: rcu_preempt kthread starved for 10490 jiffies! g6397 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=0
rcu: RCU grace-period kthread stack dump:
rcu_preempt     R  running task    29104    10      2 0x80004000
Call Trace:
 context_switch kernel/sched/core.c:3385 [inline]
 __schedule+0x9a0/0xcc0 kernel/sched/core.c:4081
 schedule+0x181/0x210 kernel/sched/core.c:4155
 schedule_timeout+0x14f/0x240 kernel/time/timer.c:1895
 rcu_gp_fqs_loop kernel/rcu/tree.c:1661 [inline]
 rcu_gp_kthread+0xed8/0x1770 kernel/rcu/tree.c:1821
 kthread+0x332/0x350 kernel/kthread.c:255
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
NMI backtrace for cpu 1
CPU: 1 PID: 8273 Comm: modprobe Not tainted 5.4.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 <IRQ>
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1fb/0x318 lib/dump_stack.c:118
 nmi_cpu_backtrace+0xaf/0x1a0 lib/nmi_backtrace.c:101
 nmi_trigger_cpumask_backtrace+0x174/0x290 lib/nmi_backtrace.c:62
 arch_trigger_cpumask_backtrace+0x10/0x20 arch/x86/kernel/apic/hw_nmi.c:38
 trigger_single_cpu_backtrace include/linux/nmi.h:164 [inline]
 rcu_dump_cpu_stacks+0x15a/0x220 kernel/rcu/tree_stall.h:254
 print_cpu_stall kernel/rcu/tree_stall.h:455 [inline]
 check_cpu_stall kernel/rcu/tree_stall.h:529 [inline]
 rcu_pending kernel/rcu/tree.c:2827 [inline]
 rcu_sched_clock_irq+0xe25/0x1ad0 kernel/rcu/tree.c:2271
 update_process_times+0x12d/0x180 kernel/time/timer.c:1726
 tick_sched_handle kernel/time/tick-sched.c:167 [inline]
 tick_sched_timer+0x263/0x420 kernel/time/tick-sched.c:1310
 __run_hrtimer kernel/time/hrtimer.c:1514 [inline]
 __hrtimer_run_queues+0x403/0x840 kernel/time/hrtimer.c:1576
 hrtimer_interrupt+0x38c/0xda0 kernel/time/hrtimer.c:1638
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1110 [inline]
 smp_apic_timer_interrupt+0x109/0x280 arch/x86/kernel/apic/apic.c:1135
 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:829
 </IRQ>
RIP: 0010:free_thread_stack+0x16d/0x590 kernel/fork.c:284
Code: c3 08 48 89 d8 48 c1 e8 03 42 80 3c 28 00 74 08 48 89 df e8 25 a4 69 00 48 8b 3b be fc ff ff ff e8 28 04 00 00 43 80 3c 2e 00 <74> 08 4c 89 e7 e8 09 a4 69 00 49 8b 1c 24 48 83 c3 08 48 89 d8 48
RSP: 0018:ffffc900021d77a8 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13
RAX: ffffffff81487433 RBX: ffff88809721f808 RCX: ffff88809cdd4480
RDX: 0000000000000000 RSI: 00000000fffffffc RDI: ffffea0002614880
RBP: ffffc900021d77e0 R08: 000000000003a768 R09: ffffed10146ffaa7
R10: ffffed10146ffaa7 R11: 0000000000000000 R12: ffff88809721f8a0
R13: dffffc0000000000 R14: 1ffff11012e43f14 R15: ffff8880a37fd528
 release_task_stack kernel/fork.c:440 [inline]
 put_task_stack+0xa3/0x130 kernel/fork.c:451
 finish_task_switch+0x3f1/0x550 kernel/sched/core.c:3256
 context_switch kernel/sched/core.c:3388 [inline]
 __schedule+0x9a8/0xcc0 kernel/sched/core.c:4081
 preempt_schedule_irq+0xc1/0x140 kernel/sched/core.c:4338
 retint_kernel+0x1b/0x2b
RIP: 0010:arch_local_irq_restore arch/x86/include/asm/paravirt.h:752 [inline]
RIP: 0010:kmem_cache_free+0xc8/0xf0 mm/slab.c:3695
Code: 58 07 00 74 42 4c 89 f7 57 9d 0f 1f 44 00 00 e8 0e 98 ca ff eb 19 e8 a7 95 ca ff 48 83 3d 07 f7 58 07 00 74 24 4c 89 f7 57 9d <0f> 1f 44 00 00 4c 89 e7 4c 89 fe e8 58 01 00 00 5b 41 5c 41 5e 41
RSP: 0018:ffffc900021d79f0 EFLAGS: 00000286 ORIG_RAX: ffffffffffffff13
RAX: ffff88809cdd4d14 RBX: ffff8880aa9eb540 RCX: ffffffff815c0597
RDX: 0000000000000000 RSI: 0000000000000008 RDI: 0000000000000286
RBP: ffffc900021d7a10 R08: ffff88809cdd4cd8 R09: fffffbfff13c852d
R10: fffffbfff13c852d R11: 0000000000000000 R12: ffffffff8147b56c
R13: 0000000000000000 R14: 0000000000000286 R15: ffff88808d594b58
 vm_area_free+0x1c/0x20 kernel/fork.c:370
 remove_vma mm/mmap.c:187 [inline]
 remove_vma_list mm/mmap.c:2582 [inline]
 __do_munmap+0x10c5/0x14c0 mm/mmap.c:2826
 __vm_munmap mm/mmap.c:2846 [inline]
 vm_munmap+0xda/0x140 mm/mmap.c:2864
 elf_map+0x236/0x310 fs/binfmt_elf.c:375
 load_elf_binary+0xfed/0x3670 fs/binfmt_elf.c:983
 search_binary_handler+0x1a5/0x660 fs/exec.c:1658
 exec_binprm fs/exec.c:1701 [inline]
 __do_execve_file+0x1573/0x1cd0 fs/exec.c:1821
 do_execveat_common fs/exec.c:1867 [inline]
 do_execve+0x33/0x40 fs/exec.c:1884
 call_usermodehelper_exec_async+0x318/0x4c0 kernel/umh.c:112
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352