The patch titled
Subject: hugetlb, userfaultfd: fix reservation restore on userfaultfd error
has been added to the -mm tree. Its filename is
hugetlb-userfaultfd-fix-reservation-restore-on-userfaultfd-error.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/hugetlb-userfaultfd-fix-reservation-restore-on-userfaultfd-error.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/hugetlb-userfaultfd-fix-reservation-restore-on-userfaultfd-error.patch
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------------------------------------------------------
From: Mina Almasry <almasrymina@xxxxxxxxxx>
Subject: hugetlb, userfaultfd: fix reservation restore on userfaultfd error
Currently in the is_continue case in hugetlb_mcopy_atomic_pte(), if we
bail out using "goto out_release_unlock;" in the cases where idx >= size,
or !huge_pte_none(), the code will detect that new_pagecache_page ==
false, and so call restore_reserve_on_error(). In this case I see
restore_reserve_on_error() delete the reservation, and the following call
to remove_inode_hugepages() will increment h->resv_hugepages causing a
100% reproducible leak.
We should treat the is_continue case similar to adding a page into the
pagecache and set new_pagecache_page to true, to indicate that there is no
reservation to restore on the error path, and we need not call
restore_reserve_on_error().
Link: https://lkml.kernel.org/r/20211116235733.3774702-1-almasrymina@xxxxxxxxxx
Fixes: c7b1850dfb41 ("hugetlb: don't pass page cache pages to restore_reserve_on_error")
Signed-off-by: Mina Almasry <almasrymina@xxxxxxxxxx>
Reported-by: James Houghton <jthoughton@xxxxxxxxxx>
Cc: Wei Xu <weixugc@xxxxxxxxxx>
Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/hugetlb.c | 8 ++++++++
1 file changed, 8 insertions(+)
--- a/mm/hugetlb.c~hugetlb-userfaultfd-fix-reservation-restore-on-userfaultfd-error
+++ a/mm/hugetlb.c
@@ -5743,6 +5743,14 @@ int hugetlb_mcopy_atomic_pte(struct mm_s
page = find_lock_page(mapping, idx);
if (!page)
goto out;
+ /*
+ * Set new_pagecache_page to true, as we've added a page to the
+ * pagecache, but userfaultfd hasn't set up a mapping for this
+ * page yet. If we bail out before setting up the mapping, we
+ * want to indicate to restore_reserve_on_error() that we've
+ * added the page to the page cache.
+ */
+ new_pagecache_page = true;
} else if (!*pagep) {
/* If a page already exists, then it's UFFDIO_COPY for
* a non-missing case. Return -EEXIST.
_
Patches currently in -mm which might be from almasrymina@xxxxxxxxxx are
hugetlb-userfaultfd-fix-reservation-restore-on-userfaultfd-error.patch
