lkml.org 
[lkml]   [2017]   [Jan]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: namespace: deadlock in dec_pid_namespaces
Nikolay Borisov <n.borisov.lkml@gmail.com> writes:

> On 20.01.2017 20:05, Eric W. Biederman wrote:
>> Nikolay Borisov <n.borisov.lkml@gmail.com> writes:
>>
>>> On 20.01.2017 15:07, Dmitry Vyukov wrote:
>>>> Hello,
>>>>
>>>> I've got the following deadlock report while running syzkaller fuzzer
>>>> on eec0d3d065bfcdf9cd5f56dd2a36b94d12d32297 of linux-next (on odroid
>>>> device if it matters):
>>
>> I am puzzled I thought we had fixed this with:
>> add7c65ca426 ("pid: fix lockdep deadlock warning due to ucount_lock")
>> But apparently not. We just moved it from hardirq to softirq context. Bah.
>>
>> Thank you very much for the report.
>>
>> Nikolay can you make your change use spinlock_irq? And have put_ucounts
>> do spin_lock_irqsave? That way we just don't care where we call this.
>
> Like the one attached?

Exactly thank you. Dmitry if you have time to test that patch and
verify it fixes your issue I would appreciate it.

> I haven't really taken careful look as to whether
> the function where _irq versions do fiddle with irq state, since this
> might cause a problem if we unconditionally enable them.

In code paths where we can sleep irqs must come in enabled or it's a
bug.

spin_lock_irq which unconditionally disables irqs is thus safe on the
allocation path.

Similary spin_unlock_irq which unconditionally enables irqs is also safe
on the allocation path.

Eric

\
 
 \ /
  Last update: 2017-01-21 01:33    [W:0.047 / U:0.596 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site