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Subject: Re: [PATCH RESEND] mm/hugetlb: Don't call region_abort if region_chg
 fails
References: <1490821682-23228-1-git-send-email-mike.kravetz@oracle.com>
 <20170329141711.50c183a7bb1bfa75e24d4426@linux-foundation.org>
 <CACT4Y+bC_AfWkG3US3f1Bkm36S+1+U2dedyJyOGN77K5joK2ZA@mail.gmail.com>
From: Mike Kravetz <mike.kravetz@oracle.com>
Message-ID: <66a8e9a2-b116-9d4c-fa74-138838a5b1d9@oracle.com>
Date: Thu, 30 Mar 2017 13:20:12 -0700
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To: Dmitry Vyukov <dvyukov@google.com>, Andrew Morton <akpm@linux-foundation.org>
Cc: "linux-mm@kvack.org" <linux-mm@kvack.org>, LKML <linux-kernel@vger.kernel.org>, Hillf Danton <hillf.zj@alibaba-inc.com>, Michal Hocko <mhocko@suse.com>, "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>, Andrey Ryabinin <aryabinin@virtuozzo.com>, Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>

On 03/30/2017 05:28 AM, Dmitry Vyukov wrote:
> On Wed, Mar 29, 2017 at 11:17 PM, Andrew Morton
> <akpm@linux-foundation.org> wrote:
>> On Wed, 29 Mar 2017 14:08:02 -0700 Mike Kravetz <mike.kravetz@oracle.com> wrote:
>>
>>>
>>> syzkaller fuzzer found this bug, that resulted in the following:
>>
>> I'll change the above to
>>
>> : syzkaller fuzzer (when using an injected kmalloc failure) found this bug,
>> : that resulted in the following:
>>
>> it's important, because this bug won't be triggered (at all easily, at
>> least) in real-world workloads.
> 
> I wonder if memory-constrained cgroups make such bugs much easier to trigger.
> 

I think you might expose some bugs with memory-constrained cgroups.  However,
it is unlikely you could trigger this bug using that method.

In this bug the injected kmalloc failure was for a 32 byte allocation.  My
guess is that it would be very very unlikely/lucky to have the allocations
done by other routines on the stack succeed, and have this 32 byte allocation
fail.   

-- 
Mike Kravetz

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