BUG: corrupted list in account_entity_enqueue

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    00c569b567c7 Merge tag 'locks-v4.21-1' of git://git.kernel..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=136d858f400000
kernel config:  https://syzkaller.appspot.com/x/.config?x=fbee5876573727cd
dashboard link: https://syzkaller.appspot.com/bug?extid=14005fa30c9a07192934
compiler:       gcc (GCC) 8.0.1 20180413 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+14005fa30c9a07192934@xxxxxxxxxxxxxxxxxxxxxxxxx

attempt to access beyond end of device
list_add corruption. next->prev should be prev (ffff8880ae62d8d8), but was  
0000000000000000. (next=ffff8880a9e1e330).
------------[ cut here ]------------
kernel BUG at lib/list_debug.c:25!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 9 Comm: ksoftirqd/0 Not tainted 4.20.0+ #393
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
RIP: 0010:__list_add_valid.cold.0+0xf/0x25 lib/list_debug.c:23
Code: e8 23 0b 32 fe e9 68 ff ff ff e8 19 0b 32 fe eb c9 4c 89 e7 e8 0f 0b  
32 fe eb 97 48 89 d9 48 c7 c7 40 c3 80 88 e8 32 ef d4 fd <0f> 0b 48 89 f1  
48 c7 c7 00 c4 80 88 48 89 de e8 1e ef d4 fd 0f 0b
RSP: 0018:ffff8880ae607218 EFLAGS: 00010082
RAX: 0000000000000075 RBX: ffff8880a9e1e330 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff81683015 RDI: 0000000000000005
RBP: ffff8880ae607230 R08: ffff8880a9e1c240 R09: ffffed1015cc5020
R10: ffffed1015cc5020 R11: ffff8880ae628107 R12: ffff888059bac2f0
R13: 1ffff11015cc0e4b R14: ffff8880ae6072b8 R15: ffff888059bac2f0
FS:  0000000000000000(0000) GS:ffff8880ae600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fe5cdd85018 CR3: 000000008679a000 CR4: 00000000001426f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <IRQ>
 __list_add include/linux/list.h:60 [inline]
 list_add include/linux/list.h:79 [inline]
 account_entity_enqueue+0x3a3/0x660 kernel/sched/fair.c:2679
 enqueue_entity+0x2af/0x1ff0 kernel/sched/fair.c:3903
 enqueue_task_fair+0x288/0x11f0 kernel/sched/fair.c:5134
 enqueue_task kernel/sched/core.c:730 [inline]
 activate_task+0x136/0x430 kernel/sched/core.c:751
 ttwu_activate kernel/sched/core.c:1643 [inline]
 ttwu_do_activate+0xd5/0x1f0 kernel/sched/core.c:1702
 ttwu_queue kernel/sched/core.c:1847 [inline]
 try_to_wake_up+0x9a3/0x1460 kernel/sched/core.c:2057
 wake_up_process+0x10/0x20 kernel/sched/core.c:2129
 hrtimer_wakeup+0x48/0x60 kernel/time/hrtimer.c:1637
 __run_hrtimer kernel/time/hrtimer.c:1389 [inline]
 __hrtimer_run_queues+0x41c/0x10d0 kernel/time/hrtimer.c:1451
 hrtimer_interrupt+0x313/0x780 kernel/time/hrtimer.c:1509
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1035 [inline]
 smp_apic_timer_interrupt+0x1a1/0x760 arch/x86/kernel/apic/apic.c:1060
 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:807
 </IRQ>
Modules linked in:
---[ end trace 8b80f5ec9872c871 ]---
RIP: 0010:__list_add_valid.cold.0+0xf/0x25 lib/list_debug.c:23
Code: e8 23 0b 32 fe e9 68 ff ff ff e8 19 0b 32 fe eb c9 4c 89 e7 e8 0f 0b  
32 fe eb 97 48 89 d9 48 c7 c7 40 c3 80 88 e8 32 ef d4 fd <0f> 0b 48 89 f1  
48 c7 c7 00 c4 80 88 48 89 de e8 1e ef d4 fd 0f 0b
RSP: 0018:ffff8880ae607218 EFLAGS: 00010082
RAX: 0000000000000075 RBX: ffff8880a9e1e330 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff81683015 RDI: 0000000000000005
RBP: ffff8880ae607230 R08: ffff8880a9e1c240 R09: ffffed1015cc5020
R10: ffffed1015cc5020 R11: ffff8880ae628107 R12: ffff888059bac2f0
R13: 1ffff11015cc0e4b R14: ffff8880ae6072b8 R15: ffff888059bac2f0
FS:  0000000000000000(0000) GS:ffff8880ae600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fe5cdd85018 CR3: 000000008679a000 CR4: 00000000001426f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


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