Re: [PATCH v1] hugetlb, userfaultfd: Fix reservation restore on userfaultfd error

From: Andrew Morton
Date: Tue Nov 16 2021 - 19:32:56 EST

On Tue, 16 Nov 2021 15:57:32 -0800 Mina Almasry <almasrymina@xxxxxxxxxx> 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().
> Cc: Wei Xu <weixugc@xxxxxxxxxx>
> Fixes: c7b1850dfb41 ("hugetlb: don't pass page cache pages to restore_reserve_on_error")

I added cc:stable to this.