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

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Date:   Mon, 3 May 2021 17:41:15 -0400
From:   Peter Xu <peterx@...hat.com>
To:     Mike Kravetz <mike.kravetz@...cle.com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        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 Mon, May 03, 2021 at 01:53:03PM -0700, Mike Kravetz wrote:
> 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>

Thanks!

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

I could be mistaken, but my understanding is it's broken from the most initial
cow support of hugetlbfs in 2006...  So if we want a fixes tag, maybe this?

Fixes: 1e8f889b10d8d ("[PATCH] Hugetlb: Copy on Write support")

-- 
Peter Xu