general protection fault in cpuacct_account_field (3)

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 7c460cf9cd1a net: aquantia: fix spelling mistake "specfiel..
git tree: net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=141f6fbd400000
kernel config: https://syzkaller.appspot.com/x/.config?x=d86f24333880b605
dashboard link: https://syzkaller.appspot.com/bug?extid=c8d99c3bc7d749791139
compiler: gcc (GCC) 8.0.1 20180413 (experimental)
CC: [fwei...@gmail.com linux-...@vger.kernel.org
mi...@kernel.org tg...@linutronix.de]

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+c8d99c...@syzkaller.appspotmail.com

IPVS: ftp: loaded support on port[0] = 21

=============================
kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] PREEMPT SMP KASAN
CPU: 1 PID: -1962184344 Comm: ksoftirqd/1 Not tainted 4.20.0-rc2+ #301
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
RIP: 0010:task_css include/linux/cgroup.h:477 [inline]
RIP: 0010:task_ca kernel/sched/cpuacct.c:43 [inline]
RIP: 0010:cpuacct_account_field+0x140/0x3d0 kernel/sched/cpuacct.c:365
Code: 26 96 08 00 85 c0 74 0d 80 3d 49 92 b2 08 00 0f 84 a4 01 00 00 49 8d
7e 10 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f
85 4e 02 00 00 4d 8b 7e 10 49 81 ff a0 1d 58 89 0f
RSP: 0018:ffff8881daf078a8 EFLAGS: 00010002
RAX: dffffc0000000000 RBX: ffff8881daf07918 RCX: 0000000000000000
RDX: 0000000000000002 RSI: 00000000ffff8881 RDI: 0000000000000011
RBP: ffff8881daf07940 R08: 0000000000000000 R09: 0000000000000000
R10: fffffbfff14a7009 R11: 0000000000000001 R12: 000000000074fa7f
R13: dffffc0000000000 R14: 0000000000000001 R15: ffff8881d9b4a440
FS: 0000000000000000(0000) GS:ffff8881daf00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000625208 CR3: 00000001c2a75000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<IRQ>
cgroup_account_cputime_field include/linux/cgroup.h:775 [inline]
task_group_account_field kernel/sched/cputime.c:108 [inline]
account_system_index_time+0x1e8/0x5d0 kernel/sched/cputime.c:171
irqtime_account_process_tick.isra.6+0x38e/0x490 kernel/sched/cputime.c:380
account_process_tick+0x282/0x350 kernel/sched/cputime.c:483
update_process_times+0x21/0x70 kernel/time/timer.c:1634
tick_sched_handle+0x9f/0x180 kernel/time/tick-sched.c:164
tick_sched_timer+0x45/0x130 kernel/time/tick-sched.c:1274
__run_hrtimer kernel/time/hrtimer.c:1398 [inline]
__hrtimer_run_queues+0x41c/0x10d0 kernel/time/hrtimer.c:1460
hrtimer_interrupt+0x313/0x780 kernel/time/hrtimer.c:1518
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1034 [inline]
smp_apic_timer_interrupt+0x1a1/0x760 arch/x86/kernel/apic/apic.c:1059
apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:804
</IRQ>
Modules linked in:
---[ end trace bb0ef84201ccc48e ]---
RIP: 0010:task_css include/linux/cgroup.h:477 [inline]
RIP: 0010:task_ca kernel/sched/cpuacct.c:43 [inline]
RIP: 0010:cpuacct_account_field+0x140/0x3d0 kernel/sched/cpuacct.c:365
Code: 26 96 08 00 85 c0 74 0d 80 3d 49 92 b2 08 00 0f 84 a4 01 00 00 49 8d
7e 10 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f
85 4e 02 00 00 4d 8b 7e 10 49 81 ff a0 1d 58 89 0f
RSP: 0018:ffff8881daf078a8 EFLAGS: 00010002
RAX: dffffc0000000000 RBX: ffff8881daf07918 RCX: 0000000000000000
RDX: 0000000000000002 RSI: 00000000ffff8881 RDI: 0000000000000011
RBP: ffff8881daf07940 R08: 0000000000000000 R09: 0000000000000000
R10: fffffbfff14a7009 R11: 0000000000000001 R12: 000000000074fa7f
R13: dffffc0000000000 R14: 0000000000000001 R15: ffff8881d9b4a440
FS: 0000000000000000(0000) GS:ffff8881daf00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000625208 CR3: 00000001c2a75000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.