Re: BUG: corrupted list in account_entity_enqueue

[syzbot]

syzbot has found a reproducer for the following crash on:

HEAD commit:    4cd1b60def51 Add linux-next specific files for 20190102
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=12b12dbf400000
kernel config:  https://syzkaller.appspot.com/x/.config?x=3bf665f887bd3d7e
dashboard link: https://syzkaller.appspot.com/bug?extid=14005fa30c9a07192934
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=10621f53400000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=154d0427400000

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

list_add corruption. next->prev should be prev (ffff8880ae72d8d8), but was  
0000000000000610. (next=ffff8880a94b64f0).
------------[ cut here ]------------
kernel BUG at lib/list_debug.c:23!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN
CPU: 1 PID: -1958513720 Comm:  Not tainted 4.20.0-next-20190102 #2
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
RIP: 0010:__list_add_valid.cold+0xf/0x3c lib/list_debug.c:23
Code: 34 fe eb d5 4c 89 e7 e8 3a 82 34 fe eb a3 4c 89 f7 e8 30 82 34 fe e9  
56 ff ff ff 4c 89 e1 48 c7 c7 40 98 81 88 e8 00 cb d6 fd <0f> 0b 48 89 f2  
4c 89 e1 4c 89 ee 48 c7 c7 80 99 81 88 e8 e9 ca d6
RSP: 0018:ffff8880ae707648 EFLAGS: 00010086
RAX: 0000000000000075 RBX: ffff8880a4783cc0 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff8167d786 RDI: ffffed1015ce0ebb
RBP: ffff8880ae707660 R08: 0000000000000075 R09: ffffed1015ce5021
R10: ffffed1015ce5020 R11: ffff8880ae728107 R12: ffff8880a94b64f0
R13: ffff8880a843a530 R14: ffff8880ae7076e8 R15: ffff8880a843a530
FS:  0000000000000000(0000) GS:ffff8880ae700000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000068 CR3: 00000000a43c7000 CR4: 00000000001406e0
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+0x3a0/0x660 kernel/sched/fair.c:2678
 enqueue_entity+0x276/0x20b0 kernel/sched/fair.c:3902
 enqueue_task_fair+0x237/0x10c0 kernel/sched/fair.c:5133
 enqueue_task kernel/sched/core.c:730 [inline]
 activate_task+0x11d/0x470 kernel/sched/core.c:751
 ttwu_activate kernel/sched/core.c:1643 [inline]
 ttwu_do_activate+0xd4/0x1f0 kernel/sched/core.c:1702
 ttwu_queue kernel/sched/core.c:1847 [inline]
 try_to_wake_up+0x997/0x1480 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+0x3a7/0x1050 kernel/time/hrtimer.c:1451
 hrtimer_interrupt+0x314/0x770 kernel/time/hrtimer.c:1509
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1035 [inline]
 smp_apic_timer_interrupt+0x18d/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 21a00246ce9209ce ]---
RIP: 0010:__list_add_valid.cold+0xf/0x3c lib/list_debug.c:23
Code: 34 fe eb d5 4c 89 e7 e8 3a 82 34 fe eb a3 4c 89 f7 e8 30 82 34 fe e9  
56 ff ff ff 4c 89 e1 48 c7 c7 40 98 81 88 e8 00 cb d6 fd <0f> 0b 48 89 f2  
4c 89 e1 4c 89 ee 48 c7 c7 80 99 81 88 e8 e9 ca d6
RSP: 0018:ffff8880ae707648 EFLAGS: 00010086
RAX: 0000000000000075 RBX: ffff8880a4783cc0 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff8167d786 RDI: ffffed1015ce0ebb
RBP: ffff8880ae707660 R08: 0000000000000075 R09: ffffed1015ce5021
R10: ffffed1015ce5020 R11: ffff8880ae728107 R12: ffff8880a94b64f0
R13: ffff8880a843a530 R14: ffff8880ae7076e8 R15: ffff8880a843a530
FS:  0000000000000000(0000) GS:ffff8880ae700000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000068 CR3: 00000000a43c7000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400