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Groups > linux.kernel > #1564020
| Path | csiph.com!aioe.org!bofh.it!news.nic.it!robomod |
|---|---|
| From | ebiederm@xmission.com (Eric W. Biederman) |
| Newsgroups | linux.kernel |
| Subject | Re: namespace: deadlock in dec_pid_namespaces |
| Date | Sat, 21 Jan 2017 01:40:01 +0100 |
| Message-ID | <t1RSN-5Ms-15@gated-at.bofh.it> (permalink) |
| References | <t1H74-7EL-19@gated-at.bofh.it> <t1Hqq-7M4-31@gated-at.bofh.it> <t1LX4-2d6-11@gated-at.bofh.it> <t1Qam-4J3-11@gated-at.bofh.it> |
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| X-Original-Cc | Dmitry Vyukov <dvyukov@google.com>, avagin <avagin@openvz.org>, serge@hallyn.com, Kees Cook <keescook@chromium.org>, Al Viro <viro@zeniv.linux.org.uk>, LKML <linux-kernel@vger.kernel.org>, syzkaller <syzkaller@googlegroups.com> |
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| Xref | csiph.com linux.kernel:1564020 |
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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
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namespace: deadlock in dec_pid_namespaces Dmitry Vyukov <dvyukov@google.com> - 2017-01-20 14:10 +0100
Re: namespace: deadlock in dec_pid_namespaces Nikolay Borisov <n.borisov.lkml@gmail.com> - 2017-01-20 14:30 +0100
Re: namespace: deadlock in dec_pid_namespaces ebiederm@xmission.com (Eric W. Biederman) - 2017-01-20 19:20 +0100
Re: namespace: deadlock in dec_pid_namespaces Nikolay Borisov <n.borisov.lkml@gmail.com> - 2017-01-20 23:50 +0100
Re: namespace: deadlock in dec_pid_namespaces ebiederm@xmission.com (Eric W. Biederman) - 2017-01-21 01:40 +0100
Re: namespace: deadlock in dec_pid_namespaces Dmitry Vyukov <dvyukov@google.com> - 2017-01-23 10:40 +0100
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