Messages in this thread Patch in this message | | | Date | Tue, 16 Nov 2021 15:57:32 -0800 | Subject | [PATCH v1] hugetlb, userfaultfd: Fix reservation restore on userfaultfd error | From | Mina Almasry <> |
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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().
Cc: Wei Xu <weixugc@google.com>
Fixes: c7b1850dfb41 ("hugetlb: don't pass page cache pages to restore_reserve_on_error") Signed-off-by: Mina Almasry <almasrymina@google.com> Reported-by: James Houghton <jthoughton@google.com> --- mm/hugetlb.c | 8 ++++++++ 1 file changed, 8 insertions(+)
diff --git a/mm/hugetlb.c b/mm/hugetlb.c index e09159c957e3..25a7a3d84607 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -5741,6 +5741,14 @@ int hugetlb_mcopy_atomic_pte(struct mm_struct *dst_mm, 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. -- 2.34.0.rc1.387.gb447b232ab-goog
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