linux-kernel - Re: Memory zeroed when made available to user process

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Message-ID: <2634793.Cb5OrAPIO5@blindfold>
Date:   Wed, 27 Jun 2018 15:18:52 +0200
From:   Richard Weinberger <richard@...ma-star.at>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     Richard Weinberger <richard.weinberger@...il.com>,
        Jefferson Carpenter <jeffersoncarpenter2@...il.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: Memory zeroed when made available to user process

Am Mittwoch, 27. Juni 2018, 15:12:48 CEST schrieb Michal Hocko:
> On Wed 27-06-18 13:29:05, Richard Weinberger wrote:
> > On Wed, Jun 27, 2018 at 11:34 AM, Jefferson Carpenter
> > <jeffersoncarpenter2@...il.com> wrote:
> > > Is there a way for a user process to mark memory as 'sensitive' or
> > > 'non-sensitive' when it is allocated?  That could allow it not to have to be
> > > zeroed before being allocated to another process.
> > 
> > Isn't this what we have Meltdown and Spectre for? ;-)
> > 
> > No, memory from the kernel is always zeroed.
> > libc offers malloc() and calloc() for this purpose.
> 
> Well, except for the weird MAP_UNINITIALIZED. Anyway agreed that this is
> a bad idea and the flag should have never been merged. I've just
> mentioned it for completness.

Oh, I forgot about the crazy nommu world. :-)

Thanks,
//richard

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