syzbot

rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 	0-...!: (10499 ticks this GP) idle=69a/1/0x4000000000000002 softirq=11711/11711 fqs=1 
	(t=10500 jiffies g=6405 q=28)
rcu: rcu_preempt kthread starved for 10498 jiffies! g6405 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=1
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 0
CPU: 0 PID: 8225 Comm: udevd 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+0x151/0x590 kernel/fork.c:280
Code: 31 f6 e8 42 af 6e 00 43 80 3c 2e 00 74 08 4c 89 e7 e8 43 a4 69 00 49 8b 1c 24 48 83 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
RSP: 0018:ffffc90001cf79e8 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13
RAX: 1ffff11014d1e731 RBX: ffff8880a68f3988 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffea0001b1fa40
RBP: ffffc90001cf7a20 R08: 000000000003a768 R09: ffffed1011ec674f
R10: ffffed1011ec674f R11: 0000000000000000 R12: ffff8880a68f3a20
R13: dffffc0000000000 R14: 1ffff11014d1e744 R15: ffff88808f633a68
 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:kfree+0x1a3/0x200 mm/slab.c:3758
Code: 48 83 3d 67 19 59 07 00 74 68 4c 89 f7 57 9d 0f 1f 44 00 00 eb 19 e8 ec b7 ca ff 48 83 3d 4c 19 59 07 00 74 51 4c 89 f7 57 9d <0f> 1f 44 00 00 5b 41 5c 41 5e 41 5f 5d c3 48 ff c9 48 89 c8 e9 c8
RSP: 0018:ffffc90001cf7c30 EFLAGS: 00000286 ORIG_RAX: ffffffffffffff13
RAX: ffff88809e5ae894 RBX: ffff8880aa8001c0 RCX: ffffffff815c0597
RDX: 0000000000000000 RSI: 0000000000000008 RDI: 0000000000000286
RBP: ffffc90001cf7c50 R08: ffff88809e5ae858 R09: fffffbfff13c8d2e
R10: fffffbfff13c8d2e R11: 0000000000000000 R12: ffff88809a30f680
R13: 1ffff9200039ef94 R14: 0000000000000286 R15: ffffffff83557ebb
 tomoyo_path_perm+0x66b/0x850 security/tomoyo/file.c:840
 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:4148
 __do_sys_symlink fs/namei.c:4169 [inline]
 __se_sys_symlink fs/namei.c:4167 [inline]
 __x64_sys_symlink+0x60/0x70 fs/namei.c:4167
 do_syscall_64+0xf7/0x1c0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x7fa370ef5517
Code: 09 01 00 00 0f 05 48 3d 00 f0 ff ff 77 02 f3 c3 48 8b 15 14 39 2b 00 f7 d8 64 89 02 83 c8 ff c3 90 90 90 b8 58 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d f1 38 2b 00 31 d2 48 29 c2 64
RSP: 002b:00007ffe0a0d8c28 EFLAGS: 00000206 ORIG_RAX: 0000000000000058
RAX: ffffffffffffffda RBX: 00000000008ee250 RCX: 00007fa370ef5517
RDX: 0000000000000002 RSI: 00007ffe0a0d8c50 RDI: 0000000000900750
RBP: 0000000000906e80 R08: 00007ffe0a0d8800 R09: 00007fa370f49de0
R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000020
R13: 00000000008f13b0 R14: 00000000008ee250 R15: 000000000000000b