From: Andrew Morton <akpm@linux-foundation.org>
To: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: linux-kernel@vger.kernel.org, mgorman@suse.de,
andi@firstfloor.org, sasha.levin@oracle.com,
kirill.shutemov@linux.intel.com, aneesh.kumar@linux.vnet.ibm.com,
linux-mm@kvack.org
Subject: Re: [PATCH] mm/hugetlb.c: add NULL check of return value of huge_pte_offset
Date: Fri, 4 Apr 2014 15:03:45 -0700 [thread overview]
Message-ID: <20140404150345.92400430db3111fe21df7c7f@linux-foundation.org> (raw)
In-Reply-To: <533efd68.435fe00a.6936.ffffa5e7SMTPIN_ADDED_BROKEN@mx.google.com>
On Fri, 04 Apr 2014 14:43:33 -0400 Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> wrote:
> huge_pte_offset() could return NULL, so we need NULL check to avoid
> potential NULL pointer dereferences.
>
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -2662,7 +2662,8 @@ static int hugetlb_cow(struct mm_struct *mm, struct vm_area_struct *vma,
> BUG_ON(huge_pte_none(pte));
> spin_lock(ptl);
> ptep = huge_pte_offset(mm, address & huge_page_mask(h));
> - if (likely(pte_same(huge_ptep_get(ptep), pte)))
> + if (likely(ptep &&
> + pte_same(huge_ptep_get(ptep), pte)))
> goto retry_avoidcopy;
> /*
> * race occurs while re-acquiring page table
> @@ -2706,7 +2707,7 @@ static int hugetlb_cow(struct mm_struct *mm, struct vm_area_struct *vma,
> */
> spin_lock(ptl);
> ptep = huge_pte_offset(mm, address & huge_page_mask(h));
> - if (likely(pte_same(huge_ptep_get(ptep), pte))) {
> + if (likely(ptep && pte_same(huge_ptep_get(ptep), pte))) {
> ClearPagePrivate(new_page);
>
> /* Break COW */
Has anyone been hitting oopses here or was this from code inspection?
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next parent reply other threads:[~2014-04-04 22:03 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <533efd68.435fe00a.6936.ffffa5e7SMTPIN_ADDED_BROKEN@mx.google.com>
2014-04-04 22:03 ` Andrew Morton [this message]
2014-04-05 0:04 ` Naoya Horiguchi
2014-04-04 18:43 Naoya Horiguchi
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