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Subject: Re: [PATCH 2/2] mm/hugetlb: Fix cow where page writtable in child
To:     Peter Xu <peterx@redhat.com>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
Cc:     Hugh Dickins <hughd@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Andrea Arcangeli <aarcange@redhat.com>,
        Axel Rasmussen <axelrasmussen@google.com>
References: <20210501144110.8784-1-peterx@redhat.com>
 <20210501144110.8784-3-peterx@redhat.com>
From:   Mike Kravetz <mike.kravetz@oracle.com>
Message-ID: <c69c12d6-1615-e528-37a7-4776abfc7200@oracle.com>
Date:   Mon, 3 May 2021 13:53:03 -0700
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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@redhat.com>
> ---
>  mm/hugetlb.c | 2 ++
>  1 file changed, 2 insertions(+)

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

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