linux-kernel - Re: [PATCH] mm: migration: deposit page table when copying a PMD migration entry.

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Message-ID: <20171030160930.bxisbzpw5pjznelj@node.shutemov.name>
Date:   Mon, 30 Oct 2017 19:09:30 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     Zi Yan <zi.yan@...t.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Zi Yan <zi.yan@...rutgers.edu>,
        Fengguang Wu <fengguang.wu@...el.com>
Subject: Re: [PATCH] mm: migration: deposit page table when copying a PMD
 migration entry.

On Mon, Oct 30, 2017 at 10:46:36AM -0400, Zi Yan wrote:
> From: Zi Yan <zi.yan@...rutgers.edu>
> 
> We need to deposit pre-allocated PTE page table when a PMD migration
> entry is copied in copy_huge_pmd(). Otherwise, we will leak the
> pre-allocated page and cause a NULL pointer dereference later
> in zap_huge_pmd().
> 
> The missing counters during PMD migration entry copy process are added
> as well.
> 
> The bug report is here: https://lkml.org/lkml/2017/10/29/214
> 
> Fixes: 84c3fc4e9c563 ("mm: thp: check pmd migration entry in common path")
> Reported-by: Fengguang Wu <fengguang.wu@...el.com>
> Signed-off-by: Zi Yan <zi.yan@...rutgers.edu>
> Cc: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>

Acked-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>

-- 
 Kirill A. Shutemov