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Date: Fri, 4 Apr 2014 15:03:45 -0700 From: Andrew Morton <akpm@...ux-foundation.org> To: Naoya Horiguchi <n-horiguchi@...jp.nec.com> Cc: linux-kernel@...r.kernel.org, mgorman@...e.de, andi@...stfloor.org, sasha.levin@...cle.com, kirill.shutemov@...ux.intel.com, aneesh.kumar@...ux.vnet.ibm.com, linux-mm@...ck.org Subject: Re: [PATCH] mm/hugetlb.c: add NULL check of return value of huge_pte_offset On Fri, 04 Apr 2014 14:43:33 -0400 Naoya Horiguchi <n-horiguchi@...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? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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