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Message-ID: <1501946504.6577.9.camel@redhat.com>
Subject: Re: [PATCH 0/2] mm,fork,security: introduce MADV_WIPEONFORK
From: Rik van Riel <riel@redhat.com>
To: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, fweimer@redhat.com,
        colm@allcosts.net, akpm@linux-foundation.org, rppt@linux.vnet.ibm.com,
        keescook@chromium.org, luto@amacapital.net, wad@chromium.org,
        mingo@kernel.org
Date: Sat, 05 Aug 2017 11:21:44 -0400
In-Reply-To: <20170804234435.lkblljl3f3ud2spm@node.shutemov.name>
References: <20170804190730.17858-1-riel@redhat.com>
         <20170804234435.lkblljl3f3ud2spm@node.shutemov.name>
Organization: Red Hat, Inc
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On Sat, 2017-08-05 at 02:44 +0300, Kirill A. Shutemov wrote:
> On Fri, Aug 04, 2017 at 03:07:28PM -0400, riel@redhat.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()?

We already have various mandatory madvise behaviors in Linux,
including MADV_REMOVE, MADV_DONTFORK, and MADV_DONTDUMP.