linux-kernel - Re: [PATCH 0/2] mm,fork,security: introduce MADV

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Message-ID: <20170804234435.lkblljl3f3ud2spm@node.shutemov.name>
Date:   Sat, 5 Aug 2017 02:44:35 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     riel@...hat.com
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        fweimer@...hat.com, colm@...costs.net, akpm@...ux-foundation.org,
        rppt@...ux.vnet.ibm.com, keescook@...omium.org,
        luto@...capital.net, wad@...omium.org, mingo@...nel.org
Subject: Re: [PATCH 0/2] mm,fork,security: introduce MADV_WIPEONFORK

On Fri, Aug 04, 2017 at 03:07:28PM -0400, riel@...hat.com wrote:
> [resend because half the recipients got dropped due to IPv6 firewall issues]
> 
> Introduce MADV_WIPEONFORK semantics, which result in a VMA being
> empty in the child process after fork. This differs from MADV_DONTFORK
> in one important way.
> 
> If a child process accesses memory that was MADV_WIPEONFORK, it
> will get zeroes. The address ranges are still valid, they are just empty.

I feel like we are repeating mistake we made with MADV_DONTNEED.

MADV_WIPEONFORK would require a specific action from kernel, ignoring
the /advise/ would likely lead to application misbehaviour.

Is it something we really want to see from madvise()?

-- 
 Kirill A. Shutemov