From: Konstantin Khlebnikov <koct9i@gmail.com>
To: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Hugh Dickins <hughd@google.com>,
Ingo Korb <ingo.korb@tu-dortmund.de>, Ning Qu <quning@google.com>,
Dave Jones <davej@redhat.com>,
Sasha Levin <sasha.levin@oracle.com>,
Andrew Morton <akpm@linux-foundation.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: PROBLEM: repeated remap_file_pages on tmpfs triggers bug on process exit
Date: Tue, 15 Jul 2014 15:33:29 +0400 [thread overview]
Message-ID: <CALYGNiM3tQUCvSPxPbum5jkhNOPeKpAVL=x3ggFmZH-QaqULcA@mail.gmail.com> (raw)
In-Reply-To: <20140715105547.C4832E00A3@blue.fi.intel.com>
On Tue, Jul 15, 2014 at 2:55 PM, Kirill A. Shutemov
<kirill.shutemov@linux.intel.com> wrote:
> Konstantin Khlebnikov wrote:
>> It seems boundng logic in do_fault_around is wrong:
>>
>> start_addr = max(address & fault_around_mask(), vma->vm_start);
>> off = ((address - start_addr) >> PAGE_SHIFT) & (PTRS_PER_PTE - 1);
>> pte -= off;
>> pgoff -= off;
>>
>> Ok, off <= 511, but it might be bigger than pte offset in pte table.
>
> I don't see how it possible: fault_around_mask() cannot be more than 0x1ff000
> (x86-64, fault_around_bytes == 2M). It means start_addr will be aligned to 2M
> boundary in this case which is start of the page table pte belong to.
>
> Do I miss something?
Nope, you're right. This fixes kernel crash but not the original problem.
Problem is caused by calling do_fault_around for _non-linear_ faiult.
In this case pgoff is shifted and might become negative during calculation.
I'll send another patch.
>
> --
> Kirill A. Shutemov
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next prev parent reply other threads:[~2014-07-15 11:33 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-07-14 12:58 Ingo Korb
2014-07-14 19:22 ` Hugh Dickins
2014-07-14 20:13 ` Konstantin Khlebnikov
2014-07-15 9:55 ` [PATCH] mm: fix faulting range in do_fault_around Konstantin Khlebnikov
2014-07-15 10:55 ` PROBLEM: repeated remap_file_pages on tmpfs triggers bug on process exit Kirill A. Shutemov
2014-07-15 11:33 ` Konstantin Khlebnikov [this message]
2014-07-15 11:54 ` Kirill A. Shutemov
2014-07-15 20:46 ` Hugh Dickins
2014-07-15 11:58 ` [PATCH] mm: do not call do_fault_around for non-linear fault Konstantin Khlebnikov
2014-07-15 15:29 ` Ingo Korb
2014-07-15 20:42 ` Andrew Morton
2014-07-15 21:07 ` Konstantin Khlebnikov
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