syzbot

rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 	1-...!: (10499 ticks this GP) idle=cae/1/0x4000000000000002 softirq=12565/12565 fqs=6 
	(t=10501 jiffies g=7577 q=188)
rcu: rcu_preempt kthread starved for 10489 jiffies! g7577 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=0
rcu: RCU grace-period kthread stack dump:
rcu_preempt     R  running task    29032    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: 8655 Comm: syz-executor.0 Not tainted 5.5.0-rc5-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:1517 [inline]
 __hrtimer_run_queues+0x403/0x840 kernel/time/hrtimer.c:1579
 hrtimer_interrupt+0x38c/0xda0 kernel/time/hrtimer.c:1641
 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:get_current arch/x86/include/asm/current.h:15 [inline]
RIP: 0010:__sanitizer_cov_trace_pc+0x4/0x50 kernel/kcov.c:186
Code: 84 00 00 00 00 00 55 48 89 e5 53 48 89 fb e8 13 00 00 00 48 8b 3d f4 f4 ed 07 48 89 de e8 84 f4 3b 00 5b 5d c3 cc 48 8b 04 24 <65> 48 8b 0c 25 c0 1d 02 00 65 8b 15 38 5f 8b 7e f7 c2 00 01 1f 00
RSP: 0018:ffffc900021b78e0 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13
RAX: ffffffff814896c6 RBX: ffffea00024044c0 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 00000000fffffffc RDI: ffffea00024044c0
RBP: ffffc900021b7908 R08: 000000000003a728 R09: ffffed10118f1ee1
R10: ffffed10118f1ee1 R11: 0000000000000000 R12: ffff8880954f19a0
R13: dffffc0000000000 R14: 00000000fffffffc R15: ffff88808c78f6f8
 free_thread_stack+0x168/0x590 kernel/fork.c:280
 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:__read_once_size include/linux/compiler.h:199 [inline]
RIP: 0010:check_kcov_mode kernel/kcov.c:155 [inline]
RIP: 0010:__sanitizer_cov_trace_pc+0x1c/0x50 kernel/kcov.c:187
Code: ed 07 48 89 de e8 84 f4 3b 00 5b 5d c3 cc 48 8b 04 24 65 48 8b 0c 25 c0 1d 02 00 65 8b 15 38 5f 8b 7e f7 c2 00 01 1f 00 75 2c <8b> 91 80 13 00 00 83 fa 02 75 21 48 8b 91 88 13 00 00 48 8b 32 48
RSP: 0018:ffffc900021b7b68 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13
RAX: ffffffff8361b545 RBX: 000000000000000e RCX: ffff88809580a040
RDX: 0000000080000000 RSI: 000000000000000e RDI: 000000000000005e
RBP: ffffc900021b7bc0 R08: ffffffff8361b617 R09: fffffbfff12c962d
R10: fffffbfff12c962d R11: 0000000000000000 R12: 0000000000000034
R13: 0000000000000034 R14: ffff88809e1deff2 R15: ffff88809e1defbf
 tomoyo_encode security/tomoyo/realpath.c:79 [inline]
 tomoyo_realpath_from_path+0x674/0x6c0 security/tomoyo/realpath.c:286
 tomoyo_get_realpath security/tomoyo/file.c:151 [inline]
 tomoyo_path_perm+0x192/0x850 security/tomoyo/file.c:822
 tomoyo_path_symlink+0x95/0xc0 security/tomoyo/tomoyo.c:206
 security_path_symlink+0xed/0x170 security/security.c:1053
 do_symlinkat+0xf3/0x3f0 fs/namei.c:4156
 __do_sys_symlink fs/namei.c:4177 [inline]
 __se_sys_symlink fs/namei.c:4175 [inline]
 __x64_sys_symlink+0x60/0x70 fs/namei.c:4175
 do_syscall_64+0xf7/0x1c0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45ac77
Code: 0f 1f 00 b8 5c 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 6d b9 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 b8 58 00 00 00 0f 05 <48> 3d 01 f0 ff ff 0f 83 4d b9 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fff1a6303f8 EFLAGS: 00000202 ORIG_RAX: 0000000000000058
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 000000000045ac77
RDX: 00007fff1a630493 RSI: 00000000004c0a37 RDI: 00007fff1a630480
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000013
R10: 0000000000000075 R11: 0000000000000202 R12: 0000000000000001
R13: 00007fff1a630430 R14: 0000000000000000 R15: 00007fff1a630440