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%3Ba=su...

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@vger.kernel.org know about it.

From f4f0a3d85b50a65a348e2b8635041d6b30f01deb Mon Sep 17 00:00:00 2001

From: "Kirill A. Shutemov" kirill.shutemov@linux.intel.com 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@linux.intel.com

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@linux.intel.... 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 Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

--- 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@linux.intel.com 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