linux-kernel - Re: Linux 5.3-rc8

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Date:   Mon, 16 Sep 2019 18:05:57 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     "Ahmed S. Darwish" <darwish.07@...il.com>
Cc:     Matthew Garrett <mjg59@...f.ucam.org>,
        "Theodore Y. Ts'o" <tytso@....edu>, Willy Tarreau <w@....eu>,
        Vito Caputo <vcaputo@...garu.com>,
        Lennart Poettering <mzxreary@...inter.de>,
        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 Mon, Sep 16, 2019 at 4:29 PM Ahmed S. Darwish <darwish.07@...il.com> wrote:
>
> Linus, in all honesty, the other case is _not_ a hypothetical .

Oh yes it is.

You're confusing "use" with "breakage".

The _use_ of getrandom(0) for key generation isn't hypothetical.

But the _breakage_ from the suggested patch that makes it time out is.

See the difference?

The thing is, to break, you have to

 (a) do that key generation at boot time

 (b) do it on an idle machine that doesn't have entropy

in order to basically reproduce the current boot-time hang situation
with the broken gdm, except with an actual "generate key".

Then you have to ignore the big warning too.

              Linus