linux-ext4 - Re: Linux 5.3-rc8

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Date:   Tue, 17 Sep 2019 17:57:43 +0200
From:   Lennart Poettering <mzxreary@...inter.de>
To:     "Theodore Y. Ts'o" <tytso@....edu>
Cc:     Willy Tarreau <w@....eu>, Matthew Garrett <mjg59@...f.ucam.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        "Ahmed S. Darwish" <darwish.07@...il.com>,
        Vito Caputo <vcaputo@...garu.com>,
        Andreas Dilger <adilger.kernel@...ger.ca>,
        Jan Kara <jack@...e.cz>, Ray Strode <rstrode@...hat.com>,
        William Jon McCann <mccann@....edu>,
        "Alexander E. Patrakov" <patrakov@...il.com>,
        zhangjs <zachary@...shancloud.com>, linux-ext4@...r.kernel.org,
        lkml <linux-kernel@...r.kernel.org>
Subject: Re: Linux 5.3-rc8

On Di, 17.09.19 08:11, Theodore Y. Ts'o (tytso@....edu) wrote:

> On Tue, Sep 17, 2019 at 09:33:40AM +0200, Martin Steigerwald wrote:
> > Willy Tarreau - 17.09.19, 07:24:38 CEST:
> > > On Mon, Sep 16, 2019 at 06:46:07PM -0700, Matthew Garrett wrote:
> > > > >Well, the patch actually made getrandom() return en error too, but
> > > > >you seem more interested in the hypotheticals than in arguing
> > > > >actualities.>
> > > > If you want to be safe, terminate the process.
> > >
> > > This is an interesting approach. At least it will cause bug reports in
> > > application using getrandom() in an unreliable way and they will
> > > check for other options. Because one of the issues with systems that
> > > do not finish to boot is that usually the user doesn't know what
> > > process is hanging.
> >
>
> I would be happy with a change which changes getrandom(0) to send a
> kill -9 to the process if it is called too early, with a new flag,
> getrandom(GRND_BLOCK) which blocks until entropy is available.  That
> leaves it up to the application developer to decide what behavior they
> want.

Note that calling getrandom(0) "too early" is not something people do
on purpose. It happens by accident, i.e. because we live in a world
where SSH or HTTPS or so is run in the initrd already, and in a world
where booting sometimes can be very very fast. So even if you write a
program and you think "this stuff should run late I'll just
getrandom(0)" it might not actually be that case IRL because people
deploy it a slightly bit differently than you initially thought in a
slightly differently equipped system with other runtime behaviour...

Lennart