mm/gup: fix memfd_pin_folios hugetlb page allocation

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From: Steve Sistare <steven.sistare@xxxxxxxxxx>

commit 9289f020da47ef04b28865589eeee3d56d4bafea upstream.

When memfd_pin_folios -> memfd_alloc_folio creates a hugetlb page, the
index is wrong.  The subsequent call to filemap_get_folios_contig thus
cannot find it, and fails, and memfd_pin_folios loops forever.  To fix,
adjust the index for the huge_page_order.

memfd_alloc_folio also forgets to unlock the folio, so the next touch of
the page calls hugetlb_fault which blocks forever trying to take the lock.
Unlock it.

Link: https://lkml.kernel.org/r/1725373521-451395-5-git-send-email-steven.sistare@xxxxxxxxxx
Fixes: 89c1905d9c14 ("mm/gup: introduce memfd_pin_folios() for pinning memfd folios")
Signed-off-by: Steve Sistare <steven.sistare@xxxxxxxxxx>
Acked-by: Vivek Kasireddy <vivek.kasireddy@xxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Jason Gunthorpe <jgg@xxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Muchun Song <muchun.song@xxxxxxxxx>
Cc: Peter Xu <peterx@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 mm/memfd.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/mm/memfd.c b/mm/memfd.c
index bfe0e7189a37..bcb131db829d 100644
--- a/mm/memfd.c
+++ b/mm/memfd.c
@@ -79,10 +79,13 @@ struct folio *memfd_alloc_folio(struct file *memfd, pgoff_t idx)
 		 * alloc from. Also, the folio will be pinned for an indefinite
 		 * amount of time, so it is not expected to be migrated away.
 		 */
-		gfp_mask = htlb_alloc_mask(hstate_file(memfd));
-		gfp_mask &= ~(__GFP_HIGHMEM | __GFP_MOVABLE);
+		struct hstate *h = hstate_file(memfd);
 
-		folio = alloc_hugetlb_folio_reserve(hstate_file(memfd),
+		gfp_mask = htlb_alloc_mask(h);
+		gfp_mask &= ~(__GFP_HIGHMEM | __GFP_MOVABLE);
+		idx >>= huge_page_order(h);
+
+		folio = alloc_hugetlb_folio_reserve(h,
 						    numa_node_id(),
 						    NULL,
 						    gfp_mask);
@@ -95,6 +98,7 @@ struct folio *memfd_alloc_folio(struct file *memfd, pgoff_t idx)
 				free_huge_folio(folio);
 				return ERR_PTR(err);
 			}
+			folio_unlock(folio);
 			return folio;
 		}
 		return ERR_PTR(-ENOMEM);
-- 
2.46.2



Patches currently in stable-queue which might be from steven.sistare@xxxxxxxxxx are

queue-6.11/mm-gup-fix-memfd_pin_folios-alloc-race-panic.patch
queue-6.11/mm-hugetlb-fix-memfd_pin_folios-resv_huge_pages-leak.patch
queue-6.11/mm-hugetlb-simplify-refs-in-memfd_alloc_folio.patch
queue-6.11/mm-hugetlb-fix-memfd_pin_folios-free_huge_pages-leak.patch
queue-6.11/mm-filemap-fix-filemap_get_folios_contig-thp-panic.patch
queue-6.11/mm-gup-fix-memfd_pin_folios-hugetlb-page-allocation.patch




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