linux-kernel - Re: [PATCH RESEND] mm/hugetlb: Don't call region_abort if region

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Date:   Thu, 30 Mar 2017 13:20:12 -0700
From:   Mike Kravetz <mike.kravetz@...cle.com>
To:     Dmitry Vyukov <dvyukov@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     "linux-mm@...ck.org" <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Hillf Danton <hillf.zj@...baba-inc.com>,
        Michal Hocko <mhocko@...e.com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Naoya Horiguchi <n-horiguchi@...jp.nec.com>
Subject: Re: [PATCH RESEND] mm/hugetlb: Don't call region_abort if region_chg
 fails

On 03/30/2017 05:28 AM, Dmitry Vyukov wrote:
> On Wed, Mar 29, 2017 at 11:17 PM, Andrew Morton
> <akpm@...ux-foundation.org> wrote:
>> On Wed, 29 Mar 2017 14:08:02 -0700 Mike Kravetz <mike.kravetz@...cle.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