syzbot

rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 	1-...!: (10499 ticks this GP) idle=e3a/1/0x4000000000000002 softirq=11375/11376 fqs=7 
	(t=10501 jiffies g=7429 q=331)
rcu: rcu_preempt kthread starved for 10487 jiffies! g7429 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=0
rcu: RCU grace-period kthread stack dump:
rcu_preempt     R  running task    28984    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: 8642 Comm: blkid 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:free_thread_stack+0x151/0x590 kernel/fork.c:280
Code: 31 f6 e8 02 8d 6f 00 43 80 3c 2e 00 74 08 4c 89 e7 e8 73 94 6a 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 55 94 6a 00 48 8b 3b be fc ff ff ff e8 28 04 00
RSP: 0018:ffffc900027478c8 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13
RAX: 1ffff11012dfdf01 RBX: ffff888096fef808 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffea0002670280
RBP: ffffc90002747900 R08: dffffc0000000000 R09: fffffbfff12c962d
R10: fffffbfff12c962d R11: 0000000000000000 R12: ffff888096fef8a0
R13: dffffc0000000000 R14: 1ffff11012dfdf14 R15: ffff888092c119f8
 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:check_memory_region+0xd/0x2e0 mm/kasan/generic.c:191
Code: 96 e5 88 4c 89 fe 31 c0 e8 63 9a ac ff eb cf cc cc cc cc cc cc cc cc cc cc cc cc cc cc 55 48 89 e5 41 57 41 56 41 55 41 54 53 <b0> 01 48 85 f6 0f 84 fd 01 00 00 48 89 fb 48 c1 eb 2f 48 81 fb fe
RSP: 0018:ffffc90002747b18 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13
RAX: 1ffffffff12552ad RBX: ffff8880a173d5c0 RCX: ffffffff8801e63b
RDX: 0000000000000001 RSI: 0000000000000008 RDI: ffff8880a173d5c0
RBP: ffffc90002747b40 R08: dffffc0000000000 R09: fffffbfff140cf2e
R10: fffffbfff140cf2e R11: 0000000000000000 R12: 1ffff920004e8f6c
R13: 00000000000000a0 R14: ffffc90002747b60 R15: dffffc0000000000
 __kasan_check_write+0x14/0x20 mm/kasan/common.c:101
 atomic64_try_cmpxchg include/asm-generic/atomic-instrumented.h:1503 [inline]
 atomic_long_try_cmpxchg_acquire include/asm-generic/atomic-long.h:442 [inline]
 __down_write kernel/locking/rwsem.c:1390 [inline]
 down_write+0x8b/0x140 kernel/locking/rwsem.c:1535
 i_mmap_lock_write include/linux/fs.h:526 [inline]
 __vma_adjust+0x6f0/0x2390 mm/mmap.c:803
 __split_vma+0x356/0x490 include/linux/mm.h:2261
 split_vma+0x7a/0xd0 mm/mmap.c:2708
 mprotect_fixup+0x6ef/0x790 mm/mprotect.c:413
 do_mprotect_pkey+0x6c2/0x8d0 mm/mprotect.c:553
 __do_sys_mprotect mm/mprotect.c:578 [inline]
 __se_sys_mprotect mm/mprotect.c:575 [inline]
 __x64_sys_mprotect+0x80/0x90 mm/mprotect.c:575
 do_syscall_64+0xf7/0x1c0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x7f440d40b447
Code: 73 01 c3 48 8d 0d 5d ad 20 00 31 d2 48 29 c2 89 11 48 83 c8 ff eb eb 90 90 90 90 90 90 90 90 90 90 90 90 b8 0a 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8d 0d 2d ad 20 00 31 d2 48 29 c2 89
RSP: 002b:00007ffdbfb0cbf8 EFLAGS: 00000206 ORIG_RAX: 000000000000000a
RAX: ffffffffffffffda RBX: 00007f440d60d000 RCX: 00007f440d40b447
RDX: 0000000000000001 RSI: 0000000000001000 RDI: 00007f440ce3f000
RBP: 00007ffdbfb0ccf0 R08: 0000000000000001 R09: 0000000000000010
R10: 00007f440cc3d5d0 R11: 0000000000000206 R12: 00007f440cc3c000
R13: 00007f440ce40180 R14: 00007f440cc3d5d0 R15: 00007f440ce3ffe0