The patch titled
Subject: mm/hugetlb: fix NULL-pointer dereference on 5-level paging machine
has been added to the -mm tree. Its filename is
mm-hugetlb-fix-null-pointer-dereference-on-5-level-paging-machine.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-hugetlb-fix-null-pointer-dereference-on-5-level-paging-machine.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-hugetlb-fix-null-pointer-dereference-on-5-level-paging-machine.patch
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------------------------------------------------------
From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Subject: mm/hugetlb: fix NULL-pointer dereference on 5-level paging machine
I made a 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.
Link: http://lkml.kernel.org/r/20171122121921.64822-1-kirill.shutemov@xxxxxxxxxxxxxxx
Fixes: c2febafc6773 ("mm: convert generic code to 5-level paging")
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> [4.11+]
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/hugetlb.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff -puN mm/hugetlb.c~mm-hugetlb-fix-null-pointer-dereference-on-5-level-paging-machine mm/hugetlb.c
--- a/mm/hugetlb.c~mm-hugetlb-fix-null-pointer-dereference-on-5-level-paging-machine
+++ a/mm/hugetlb.c
@@ -4635,7 +4635,9 @@ pte_t *huge_pte_alloc(struct mm_struct *
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) {
_
Patches currently in -mm which might be from kirill.shutemov@xxxxxxxxxxxxxxx are
mm-hugetlb-fix-null-pointer-dereference-on-5-level-paging-machine.patch
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