linux-kernel - Re: Linux 5.3-rc8

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Date:   Tue, 17 Sep 2019 01:29:22 +0200
From:   "Ahmed S. Darwish" <darwish.07@...il.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
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 04:18:00PM -0700, Linus Torvalds wrote:
> On Mon, Sep 16, 2019 at 4:11 PM Matthew Garrett <mjg59@...f.ucam.org> wrote:
> >
> > In one case we have "Systems don't boot, but you can downgrade your
> > kernel" and in the other case we have "Your cryptographic keys are weak
> > and you have no way of knowing unless you read dmesg", and I think
> > causing boot problems is the better outcome here.
> 
> Or: In one case you have a real and present problem. In the other
> case, people are talking hypotheticals.
>

Linus, in all honesty, the other case is _not_ a hypothetical . For
example, here is a fresh comment on LWN from gnupg developers:

    https://lwn.net/Articles/799352

It's about this libgnupg code:

    => https://dev.gnupg.org/source/libgcrypt.git

    => random/rdlinux.c:
    
    /* If we have a modern operating system, we first try to use the new
     * getentropy function.  That call guarantees that the kernel's
     * RNG has been properly seeded before returning any data.  This
     * is different from /dev/urandom which may, due to its
     * non-blocking semantics, return data even if the kernel has
     * not been properly seeded.  And it differs from /dev/random by never
     * blocking once the kernel is seeded.  */
    #if defined(HAVE_GETENTROPY) || defined(__NR_getrandom)
    do {
        ...
        ret = getentropy (buffer, nbytes);
        ...
    } while (ret == -1 && errno == EINTR);

thanks,

-- 
Ahmed Darwish
http://darwish.chasingpointers.com