Re: WARNING in free_kthread_struct

[Dmitry Vyukov]

On Tue, Nov 7, 2017 at 3:54 PM, Dmitry Vyukov <dvyukov@xxxxxxxxxx> wrote:
> On Tue, Nov 7, 2017 at 3:46 PM, syzbot
> <bot+28a52b4b1430f7b2e8ced22340031dab2a0e728a@xxxxxxxxxxxxxxxxxxxxxxxxx>
> wrote:
>> Hello,
>>
>> syzkaller hit the following crash on
>> 0f611fb6dcc0d6d91b4e1fec911321f434a3b858
>> git://git.cmpxchg.org/linux-mmots.git/master
>> compiler: gcc (GCC) 7.1.1 20170620
>> .config is attached
>> Raw console output is attached.
>> C reproducer is attached
>> syzkaller reproducer is attached. See https://goo.gl/kgGztJ
>> for information about syzkaller reproducers
>
>
> This also happens on linux-next (e.g. on current HEAD
> 8b82a8a7ab53ee1a065ac69c835737a701f46b2e), but not on Linus tree.
>
> Seems to be added by :
>
> commit 05e3db95ebfc5c06a29a1d8c7a3e02f46f3a25a7
> Author: Shaohua Li
> Date:   Thu Sep 14 14:02:04 2017 -0700
>     kthread: add a mechanism to store cgroup info
>
> This severe hurts our testing, so far this crashed 133565 VMs.
>
>
>
>> WARNING: CPU: 0 PID: 4918 at kernel/kthread.c:87
>> free_kthread_struct+0xa2/0xe0 kernel/kthread.c:87
>> Kernel panic - not syncing: panic_on_warn set ...
>>
>> CPU: 0 PID: 4918 Comm: modprobe Not tainted 4.14.0-rc5-mm1+ #20
>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
>> Google 01/01/2011
>> Call Trace:
>>  <IRQ>
>>  __dump_stack lib/dump_stack.c:16 [inline]
>>  dump_stack+0x194/0x257 lib/dump_stack.c:52
>>  panic+0x1e4/0x41c kernel/panic.c:183
>>  __warn+0x1c4/0x1e0 kernel/panic.c:546
>>  report_bug+0x211/0x2d0 lib/bug.c:183
>>  fixup_bug+0x40/0x90 arch/x86/kernel/traps.c:177
>>  do_trap_no_signal arch/x86/kernel/traps.c:211 [inline]
>>  do_trap+0x260/0x390 arch/x86/kernel/traps.c:260
>>  do_error_trap+0x120/0x390 arch/x86/kernel/traps.c:297
>>  do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:310
>>  invalid_op+0x18/0x20 arch/x86/entry/entry_64.S:905
>> RIP: 0010:free_kthread_struct+0xa2/0xe0 kernel/kthread.c:87
>> RSP: 0000:ffff8801db207768 EFLAGS: 00010206
>> RAX: ffff8801c431e680 RBX: ffff8801c548f400 RCX: ffffffff8148d7e2
>> RDX: 0000000000000100 RSI: 0000000000000000 RDI: ffff8801c548f4b8
>> RBP: ffff8801db207770 R08: 0000000000000001 R09: 1ffff1003b640edc
>> R10: ffff8801db2076a8 R11: 0000000000000004 R12: 1ffff1003b640ef0
>> R13: 1ffff1003b640ef4 R14: 0000000000000000 R15: ffff8801db2077e0
>>  free_task+0x134/0x1a0 kernel/fork.c:390
>>  __put_task_struct+0x229/0x3b0 kernel/fork.c:668
>>  put_task_struct include/linux/sched/task.h:95 [inline]
>>  delayed_put_task_struct+0xca/0x3d0 kernel/exit.c:180
>>  __rcu_reclaim kernel/rcu/rcu.h:172 [inline]
>>  rcu_do_batch kernel/rcu/tree.c:2676 [inline]
>>  invoke_rcu_callbacks kernel/rcu/tree.c:2930 [inline]
>>  __rcu_process_callbacks kernel/rcu/tree.c:2897 [inline]
>>  rcu_process_callbacks+0xd74/0x17d0 kernel/rcu/tree.c:2914
>>  __do_softirq+0x2d7/0xb85 kernel/softirq.c:284
>>  invoke_softirq kernel/softirq.c:364 [inline]
>>  irq_exit+0x1cc/0x200 kernel/softirq.c:405
>>  exiting_irq arch/x86/include/asm/apic.h:540 [inline]
>>  smp_apic_timer_interrupt+0x16b/0x700 arch/x86/kernel/apic/apic.c:1052
>>  apic_timer_interrupt+0x9d/0xb0 arch/x86/entry/entry_64.S:770
>>  </IRQ>
>> RIP: 0010:__read_once_size include/linux/compiler.h:276 [inline]
>> RIP: 0010:compound_head include/linux/page-flags.h:146 [inline]
>> RIP: 0010:PageSwapBacked include/linux/page-flags.h:287 [inline]
>> RIP: 0010:mm_counter_file include/linux/mm.h:1522 [inline]
>> RIP: 0010:alloc_set_pte+0x71a/0x1880 mm/memory.c:3420
>> RSP: 0000:ffff8801c402f3e0 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff11
>> RAX: dffffc0000000000 RBX: ffff8801c402fb80 RCX: ffffffff81987189
>> RDX: 1ffff10038805e98 RSI: ffffea00076cb000 RDI: ffffea00076cb020
>> RBP: ffff8801c402f528 R08: 0000000000000001 R09: 1ffff10038805e0a
>> R10: ffff8801c402ef88 R11: 0000000000000003 R12: 1ffff10038805e84
>> R13: 1ffff10038805e98 R14: 0000000000000025 R15: ffffea00076cafe0
>>  filemap_map_pages+0x1080/0x15d0 mm/filemap.c:2680
>>  do_fault_around mm/memory.c:3567 [inline]
>>  do_read_fault mm/memory.c:3601 [inline]
>>  do_fault mm/memory.c:3706 [inline]
>>  handle_pte_fault mm/memory.c:3936 [inline]
>>  __handle_mm_fault+0x1f57/0x39c0 mm/memory.c:4060
>>  handle_mm_fault+0x334/0x8d0 mm/memory.c:4097
>>  __do_page_fault+0x5bd/0xd60 arch/x86/mm/fault.c:1438
>>  do_page_fault+0xee/0x720 arch/x86/mm/fault.c:1514
>>  page_fault+0x22/0x30 arch/x86/entry/entry_64.S:1066
>> RIP: 0033:0x7fe25f595390
>> RSP: 002b:00007ffeb59a5f08 EFLAGS: 00010202
>> RAX: 0000000000000000 RBX: 00007ffeb59a72a8 RCX: 0000563871b59660
>> RDX: 00005638719547f0 RSI: 00007ffeb59a72a8 RDI: 0000000000000004
>> RBP: 00007ffeb59a72a8 R08: 00007ffeb59a5f7c R09: 0000000000000000
>> R10: 0000000000000000 R11: 00007fe25f595390 R12: 0000000000000004
>> R13: 0000563871954608 R14: 0000000000000000 R15: 0000000000000000
>> Dumping ftrace buffer:
>>    (ftrace buffer empty)
>> Kernel Offset: disabled
>> Rebooting in 86400 seconds..
>>
>>
>> ---
>> This bug is generated by a dumb bot. It may contain errors.
>> See https://goo.gl/tpsmEJ for details.
>> Direct all questions to syzkaller@xxxxxxxxxxxxxxxxx
>> Please credit me with: Reported-by: syzbot <syzkaller@xxxxxxxxxxxxxxxx>
>>


Shaohua, please also follow this part:

\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/

>> syzbot will keep track of this bug report.
>> Once a fix for this bug is committed, please reply to this email with:
>> #syz fix: exact-commit-title

This will greatly help to keep the whole process running and report
new bugs in future.


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>> report.
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>>
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