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authorKirill A. Shutemov <kirill.shutemov@linux.intel.com>2017-11-29 16:11:30 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2017-11-29 18:40:43 -0800
commitf4f0a3d85b50a65a348e2b8635041d6b30f01deb (patch)
tree11b100039752f93f1ca110a7c8f02cae39448f7a /mm
parent5d38f049cee1e1c4a7ac55aa79d37d01ddcc3860 (diff)
downloadlwn-f4f0a3d85b50a65a348e2b8635041d6b30f01deb.tar.gz
lwn-f4f0a3d85b50a65a348e2b8635041d6b30f01deb.zip
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@linux.intel.com Fixes: c2febafc6773 ("mm: convert generic code to 5-level paging") Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Acked-by: Vlastimil Babka <vbabka@suse.cz> Acked-by: Michal Hocko <mhocko@suse.com> Cc: <stable@vger.kernel.org> [4.11+] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/hugetlb.c4
1 files changed, 3 insertions, 1 deletions
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 698e8fb34031..9a334f5fb730 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -4635,7 +4635,9 @@ 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) {