Re: [PATCH v2] hugetlb, userfaultfd: Fix reservation restore on userfaultfd error

From: Mike Kravetz
Date: Wed Nov 17 2021 - 15:44:34 EST

On 11/17/21 11:38, Mina Almasry wrote:
> 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(). Rename new_pagecache_page to
> page_in_pagecache to make that clear.
> Cc: Wei Xu <weixugc@xxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> 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>
> ---
> Changes in v2:
> - Renamed new_pagecache_page to page_in_pagecache
> - Removed unnecessary comment after the name update.
> - Cc: stable

Thanks for making the changes!

Reviewed-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>

Mike Kravetz