From fce580519b23cad29f4fce84fd56115fd06a132f Mon Sep 17 00:00:00 2001 From: Mike Kravetz Date: Thu, 12 Jan 2017 12:19:18 +1100 Subject: [PATCH] userfaultfd: hugetlbfs: reserve count on error in __mcopy_atomic_hugetlb Orabug: 21685254 If __mcopy_atomic_hugetlb exits with an error, put_page will be called if a huge page was allocated and needs to be freed. If a reservation was associated with the huge page, the PagePrivate flag will be set. Clear PagePrivate before calling put_page/free_huge_page so that the global reservation count is not incremented. Link: http://lkml.kernel.org/r/20161216144821.5183-26-aarcange@redhat.com Signed-off-by: Mike Kravetz Signed-off-by: Andrea Arcangeli Cc: "Dr. David Alan Gilbert" Cc: Hillf Danton Cc: Michael Rapoport Cc: Mike Rapoport Cc: Pavel Emelyanov Signed-off-by: Andrew Morton (cherry picked from linux-next next-20170117 commit afcc2616d4284859d8f70bbdfa6c9ca92fbb08ed) Signed-off-by: Mike Kravetz Reviewed-by: Dhaval Giani Signed-off-by: Dhaval Giani --- mm/userfaultfd.c | 17 ++++++++++++++++- 1 file changed, 16 insertions(+), 1 deletion(-) diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index 8b1c09b5f8cb..b95750925cc3 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -301,8 +301,23 @@ retry: out_unlock: up_read(&dst_mm->mmap_sem); out: - if (page) + if (page) { + /* + * We encountered an error and are about to free a newly + * allocated huge page. It is possible that there was a + * reservation associated with the page that has been + * consumed. See the routine restore_reserve_on_error + * for details. Unfortunately, we can not call + * restore_reserve_on_error now as it would require holding + * mmap_sem. Clear the PagePrivate flag so that the global + * reserve count will not be incremented in free_huge_page. + * The reservation map will still indicate the reservation + * was consumed and possibly prevent later page allocation. + * This is better than leaking a global reservation. + */ + ClearPagePrivate(page); put_page(page); + } BUG_ON(copied < 0); BUG_ON(err > 0); BUG_ON(!copied && !err); -- 2.50.1