[merged mm-hotfixes-stable] mm-hugetlb-fix-memfd_pin_folios-free_huge_pages-leak.patch removed from -mm tree

[merged mm-hotfixes-stable] mm-hugetlb-fix-memfd_pin_folios-free_huge_pages-leak.patch removed from -mm tree

[Andrew Morton]

The quilt patch titled
     Subject: mm/hugetlb: fix memfd_pin_folios free_huge_pages leak
has been removed from the -mm tree.  Its filename was
     mm-hugetlb-fix-memfd_pin_folios-free_huge_pages-leak.patch

This patch was dropped because it was merged into the mm-hotfixes-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

------------------------------------------------------
From: Steve Sistare <steven.sistare@oracle.com>
Subject: mm/hugetlb: fix memfd_pin_folios free_huge_pages leak
Date: Tue, 3 Sep 2024 07:25:18 -0700

memfd_pin_folios followed by unpin_folios fails to restore free_huge_pages
if the pages were not already faulted in, because the folio refcount for
pages created by memfd_alloc_folio never goes to 0.  memfd_pin_folios
needs another folio_put to undo the folio_try_get below:

memfd_alloc_folio()
  alloc_hugetlb_folio_nodemask()
    dequeue_hugetlb_folio_nodemask()
      dequeue_hugetlb_folio_node_exact()
        folio_ref_unfreeze(folio, 1);    ; adds 1 refcount
  folio_try_get()                        ; adds 1 refcount
  hugetlb_add_to_page_cache()            ; adds 512 refcount (on x86)

With the fix, after memfd_pin_folios + unpin_folios, the refcount for the
(unfaulted) page is 512, which is correct, as the refcount for a faulted
unpinned page is 513.

Link: https://lkml.kernel.org/r/1725373521-451395-3-git-send-email-steven.sistare@oracle.com
Fixes: 89c1905d9c14 ("mm/gup: introduce memfd_pin_folios() for pinning memfd folios")
Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Acked-by: Vivek Kasireddy <vivek.kasireddy@intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Peter Xu <peterx@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/gup.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/mm/gup.c~mm-hugetlb-fix-memfd_pin_folios-free_huge_pages-leak
+++ a/mm/gup.c
@@ -3615,7 +3615,7 @@ long memfd_pin_folios(struct file *memfd
 	pgoff_t start_idx, end_idx, next_idx;
 	struct folio *folio = NULL;
 	struct folio_batch fbatch;
-	struct hstate *h;
+	struct hstate *h = NULL;
 	long ret = -EINVAL;
 
 	if (start < 0 || start > end || !max_folios)
@@ -3659,6 +3659,8 @@ long memfd_pin_folios(struct file *memfd
 							     &fbatch);
 			if (folio) {
 				folio_put(folio);
+				if (h)
+					folio_put(folio);
 				folio = NULL;
 			}
 
_

Patches currently in -mm which might be from steven.sistare@oracle.com are