linux-kernel - Re: [PATCH 2/2] mm/hugetlb: Fix cow where page writtable in child

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Date:   Mon, 3 May 2021 13:53:03 -0700
From:   Mike Kravetz <mike.kravetz@...cle.com>
To:     Peter Xu <peterx@...hat.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Cc:     Hugh Dickins <hughd@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Axel Rasmussen <axelrasmussen@...gle.com>
Subject: Re: [PATCH 2/2] mm/hugetlb: Fix cow where page writtable in child

On 5/1/21 7:41 AM, Peter Xu wrote:
> When fork() and copy hugetlb page range, we'll remember to wrprotect src pte if
> needed, however we forget about the child!  Without it, the child will be able
> to write to parent's pages when mapped as PROT_READ|PROT_WRITE and MAP_PRIVATE,
> which will cause data corruption in the parent process.
> 
> This issue can also be exposed by "memfd_test hugetlbfs" kselftest (if it can
> pass the F_SEAL_FUTURE_WRITE test first, though).
> 
> Signed-off-by: Peter Xu <peterx@...hat.com>
> ---
>  mm/hugetlb.c | 2 ++
>  1 file changed, 2 insertions(+)

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

I think we need to add, "Fixes: 4eae4efa2c29" as this is now in v5.12
-- 
Mike Kravetz