syzbot

rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 	0-...!: (10499 ticks this GP) idle=bea/1/0x4000000000000002 softirq=10739/10739 fqs=41 
	(t=10500 jiffies g=6073 q=50)
rcu: rcu_preempt kthread starved for 10418 jiffies! g6073 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: 8154 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:check_kcov_mode kernel/kcov.c:79 [inline]
RIP: 0010:__sanitizer_cov_trace_pc+0x22/0x50 kernel/kcov.c:102
Code: 64 02 3b 00 5b 5d c3 cc 48 8b 04 24 65 48 8b 0c 25 c0 1d 02 00 65 8b 15 b8 81 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 8d 7e 01 8b 89 84
RSP: 0018:ffffc90001e27420 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13
RAX: ffffffff81487326 RBX: ffffea000245ed00 RCX: ffff888098f940c0
RDX: 0000000000000000 RSI: 00000000fffffffc RDI: ffffea000245ed00
RBP: ffffc90001e27448 R08: 000000000003a768 R09: ffffed10145822e7
R10: ffffed10145822e7 R11: 0000000000000000 R12: ffff88808cebdf20
R13: dffffc0000000000 R14: 00000000fffffffc R15: ffff8880a2c11728
 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:arch_local_irq_restore arch/x86/include/asm/paravirt.h:752 [inline]
RIP: 0010:qlink_free+0x91/0xb0 mm/kasan/quarantine.c:151
Code: 58 07 00 74 35 4c 89 f7 57 9d 0f 1f 44 00 00 e8 15 1b ca ff eb 19 e8 ae 18 ca ff 48 83 3d 0e 7a 58 07 00 74 17 4c 89 f7 57 9d <0f> 1f 44 00 00 5b 41 5e 41 5f 5d c3 0f 0b 0f 0b 0f 0b 0f 0b 90 66
RSP: 0018:ffffc90001e276a8 EFLAGS: 00000286 ORIG_RAX: ffffffffffffff13
RAX: ffff888098f94954 RBX: ffff888091e2d000 RCX: ffffffff815c0597
RDX: 0000000000000000 RSI: 0000000000000008 RDI: 0000000000000286
RBP: ffffc90001e276c0 R08: ffff888098f94918 R09: fffffbfff13c8d2f
R10: fffffbfff13c8d2f R11: 0000000000000000 R12: ffff888091e2d000
R13: 0000000000000200 R14: 0000000000000286 R15: ffff8880aa812a80
 qlist_free_all mm/kasan/quarantine.c:167 [inline]
 quarantine_reduce+0x15e/0x1d0 mm/kasan/quarantine.c:260
 __kasan_kmalloc+0x46/0x1b0 mm/kasan/common.c:493
 kasan_slab_alloc+0xf/0x20 mm/kasan/common.c:520
 slab_post_alloc_hook mm/slab.h:584 [inline]
 slab_alloc mm/slab.c:3320 [inline]
 kmem_cache_alloc_trace+0x1fa/0x2f0 mm/slab.c:3549
 kmalloc include/linux/slab.h:556 [inline]
 kzalloc include/linux/slab.h:670 [inline]
 kernfs_fop_open+0x3a9/0xc20 fs/kernfs/file.c:647
 do_dentry_open+0x740/0x10c0 fs/open.c:797
 vfs_open+0x73/0x80 fs/open.c:914
 do_last fs/namei.c:3412 [inline]
 path_openat+0x1397/0x44a0 fs/namei.c:3529
 do_filp_open+0x192/0x3d0 fs/namei.c:3559
 do_sys_open+0x29f/0x560 fs/open.c:1097
 __do_sys_open fs/open.c:1115 [inline]
 __se_sys_open fs/open.c:1110 [inline]
 __x64_sys_open+0x87/0x90 fs/open.c:1110
 do_syscall_64+0xf7/0x1c0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x7f2260db5120
Code: 48 8b 15 1b 4d 2b 00 f7 d8 64 89 02 83 c8 ff c3 90 90 90 90 90 90 90 90 90 90 83 3d d5 a4 2b 00 00 75 10 b8 02 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 31 c3 48 83 ec 08 e8 5e 8c 01 00 48 89 04 24
RSP: 002b:00007ffd6e7b1a68 EFLAGS: 00000246 ORIG_RAX: 0000000000000002
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f2260db5120
RDX: 0000000000000124 RSI: 0000000000080000 RDI: 00007ffd6e7b1b10
RBP: 0000000000f8c744 R08: 0000000000f8c744 R09: 00007f2260e0ac20
R10: 7269762f73656369 R11: 0000000000000246 R12: 0000000000f83e60
R13: 0000000000f83f50 R14: 0000000000f72250 R15: 0000000000f77e10