Messages in this thread Patch in this message |  | | From | "Kirill A. Shutemov" <> | Subject | [PATCH] mm/hugetlb: Fix NULL-pointer dereference on 5-level paging machine | Date | Wed, 22 Nov 2017 15:19:21 +0300 |
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I've made mistake during converting hugetlb code to 5-level paging: in huge_pte_alloc() we have to use p4d_alloc(), not p4d_offset(). Otherwise it leads to crash -- NULL-pointer dereference in pud_alloc() if p4d table is not yet allocated.
It only can happen in 5-level paging mode. In 4-level paging mode p4d_offset() always returns pgd, so we are fine.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Fixes: c2febafc6773 ("mm: convert generic code to 5-level paging") Cc: <stable@vger.kernel.org> # v4.11+ --- mm/hugetlb.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 2d2ff5e8bf2b..94a4c0b63580 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -4617,7 +4617,9 @@ pte_t *huge_pte_alloc(struct mm_struct *mm, pte_t *pte = NULL; pgd = pgd_offset(mm, addr); - p4d = p4d_offset(pgd, addr); + p4d = p4d_alloc(mm, pgd, addr); + if (!p4d) + return NULL; pud = pud_alloc(mm, p4d, addr); if (pud) { if (sz == PUD_SIZE) { -- 2.15.0
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