This is a note to let you know that I've just added the patch titled
mm/hugetlb: fix NULL-pointer dereference on 5-level paging machine
to the 4.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
mm-hugetlb-fix-null-pointer-dereference-on-5-level-paging-machine.patch
and it can be found in the queue-4.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From f4f0a3d85b50a65a348e2b8635041d6b30f01deb Mon Sep 17 00:00:00 2001
From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Date: Wed, 29 Nov 2017 16:11:30 -0800
Subject: mm/hugetlb: fix NULL-pointer dereference on 5-level paging machine
From: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
commit f4f0a3d85b50a65a348e2b8635041d6b30f01deb upstream.
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>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
mm/hugetlb.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -4625,7 +4625,9 @@ 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 stable-queue which might be from kirill.shutemov@xxxxxxxxxxxxxxx are
queue-4.14/mm-fix-device-dax-pud-write-faults-triggered-by-get_user_pages.patch
queue-4.14/mm-hugetlb-fix-null-pointer-dereference-on-5-level-paging-machine.patch
queue-4.14/mm-thp-do-not-make-page-table-dirty-unconditionally-in-touch_pd.patch
queue-4.14/mm-madvise.c-fix-madvise-infinite-loop-under-special-circumstances.patch