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Subject: Re: memory leak in alloc_huge_page
To: Dmitry Vyukov <dvyukov@google.com>
References: <CACT4Y+amx86fBiqoCpFzTa=nOGayDjLb5CENEskrKeRTy6NSQw@mail.gmail.com>
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 <CACT4Y+Zsw23LiBhakWUFfO88OuuHsV588g3T9UPfMKxRBLojGQ@mail.gmail.com>
From: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
        Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>,
        Hillf Danton <hillf.zj@alibaba-inc.com>,
        David Rientjes <rientjes@google.com>,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>, Hugh Dickins <hughd@google.com>,
        Greg Thelen <gthelen@google.com>,
        syzkaller <syzkaller@googlegroups.com>,
        Kostya Serebryany <kcc@google.com>,
        Alexander Potapenko <glider@google.com>,
        Sasha Levin <sasha.levin@oracle.com>,
        Eric Dumazet <edumazet@google.com>
Message-ID: <565E413D.8050608@oracle.com>
Date: Tue, 1 Dec 2015 16:54:21 -0800
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On 12/01/2015 11:45 AM, Dmitry Vyukov wrote:
> On Tue, Dec 1, 2015 at 7:52 PM, Mike Kravetz <mike.kravetz@oracle.com> wrote:
>> On 12/01/2015 06:04 AM, Dmitry Vyukov wrote:

>>> There seems to be another leak if nrg is not NULL on this path, but
>>> it's not what happens in my case since the WARNING does not fire.
>>
>> If nrg is not NULL, then it was added to the resv map and 'should' be
>> free'ed when the map is free'ed.  This is not optimal, but I do not
>> think it would lead to a leak.  I'll take a close look at this code
>> with an emphasis on the leak you discovered.
> 
> 
> Hi Mike,
> 
> Note that it's not just a leak report, it is an actual leak. You
> should be able to reproduce it.
> 

OK, finally found the bug which is in region_del().  It does not correctly
handle a "placeholder" region descriptor that is left after an aborted
operation when the start of the region to be deleted is for the same page.

I will have a patch shortly, after some testing.

-- 
Mike Kravetz