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From: Pavel Machek <pavel@ucw.cz>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: "Ahmed S. Darwish" <darwish.07@gmail.com>,
	"Theodore Y. Ts'o" <tytso@mit.edu>,
	Andreas Dilger <adilger.kernel@dilger.ca>,
	Jan Kara <jack@suse.cz>, Ray Strode <rstrode@redhat.com>,
	William Jon McCann <mccann@jhu.edu>,
	"Alexander E. Patrakov" <patrakov@gmail.com>,
	zhangjs <zachary@baishancloud.com>,
	linux-ext4@vger.kernel.org,
	Lennart Poettering <lennart@poettering.net>,
	lkml <linux-kernel@vger.kernel.org>
Subject: chaos generating driver was Re: Linux 5.3-rc8
Date: Mon, 23 Sep 2019 22:49:45 +0200
Message-ID: <20190923204944.GA1107@bug> (raw)
In-Reply-To: <CAHk-=wjuVT+2oj_U2V94MBVaJdWsbo1RWzy0qXQSMAUnSaQzxw@mail.gmail.com>

Hi!

> >     => src/random-seed/random-seed.c:
> >     /*
> >      * Let's make this whole job asynchronous, i.e. let's make
> >      * ourselves a barrier for proper initialization of the
> >      * random pool.
> >      */
...
> >      k = getrandom(buf, buf_size, GRND_NONBLOCK);
> >      if (k < 0 && errno == EAGAIN && synchronous) {
> >          log_notice("Kernel entropy pool is not initialized yet, "
> >                     "waiting until it is.");
> >
> >          k = getrandom(buf, buf_size, 0); /* retry synchronously */
> >      }
> 
> Yeah, the above is yet another example of completely broken garbage.
> 
> You can't just wait and block at boot. That is simply 100%
> unacceptable, and always has been, exactly because that may
> potentially mean waiting forever since you didn't do anything that
> actually is likely to add any entropy.

Hmm. This actually points to a solution, and I believe solution is in the
kernel. Userspace is not the best place to decide what is the best way to
generate entropy.

> As mentioned, this has already historically been a huge issue on
> embedded devices, and with disks turnign not just to NVMe but to
> actual polling nvdimm/xpoint/flash, the amount of true "entropy"
> randomness we can give at boot is very questionable.
> 
> We can (and will) continue to do a best-effort thing (including very
> much using rdread and friends), but the whole "wait for entropy"
> simply *must* stop.

And we can stop it... from kernel, and without hacks. Simply by generating some
entropy. We do not need to sit quietly while userspace waits for entropy to appear.

We can for example do some reads from the disk. (find / should be good for generating
entropy on many systems). For systems with rtc but not timestamp counter, we can
actually just increase register, then read it from interrupt...
...to get precise timings. We know system is blocked waiting for entropy, we can
do expensive things we would not "normally" do.

Yes, it would probably mean new kind of "driver" whose purpose is to generate some
kind of activity so that interrupts happen and entropy is generated... But that is
still better solution than fixing all of the userspace.

(With some proposals here, userspace _could_ do 

while (getrandom() == -EINVAL) {
    system("find / &");
    sleep(1);
}

...but I believe we really want to do it once, in kernel, and less hacky than this)

Best regards,
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

  parent reply index

Thread overview: 211+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <CAHk-=whBQ+6c-h+htiv6pp8ndtv97+45AH9WvdZougDRM6M4VQ@mail.gmail.com>
2019-09-10  4:21 ` Ahmed S. Darwish
2019-09-10 11:33   ` Linus Torvalds
2019-09-10 12:21     ` Linus Torvalds
2019-09-10 17:33     ` Ahmed S. Darwish
2019-09-10 17:47       ` Reindl Harald
2019-09-10 18:21       ` Linus Torvalds
2019-09-11 16:07         ` Theodore Y. Ts'o
2019-09-11 16:45           ` Linus Torvalds
2019-09-11 17:00             ` Linus Torvalds
2019-09-11 17:36               ` Theodore Y. Ts'o
2019-09-12  3:44                 ` Ahmed S. Darwish
2019-09-12  8:25                   ` Theodore Y. Ts'o
2019-09-12 11:34                     ` Linus Torvalds
2019-09-12 11:58                       ` Willy Tarreau
2019-09-14 12:25                       ` [PATCH RFC] random: getrandom(2): don't block on non-initialized entropy pool Ahmed S. Darwish
2019-09-14 14:08                         ` Alexander E. Patrakov
2019-09-15  5:22                           ` [PATCH RFC v2] random: optionally block in getrandom(2) when the CRNG is uninitialized Theodore Y. Ts'o
2019-09-15  8:17                             ` [PATCH RFC v3] random: getrandom(2): optionally block when " Ahmed S. Darwish
2019-09-15  8:59                               ` Lennart Poettering
2019-09-15  9:30                                 ` Willy Tarreau
2019-09-15 10:02                                   ` Ahmed S. Darwish
2019-09-15 10:40                                     ` Willy Tarreau
2019-09-15 10:55                                       ` Ahmed S. Darwish
2019-09-15 11:17                                         ` Willy Tarreau
2019-09-15 17:32                             ` [PATCH RFC v2] random: optionally block in getrandom(2) when the " Linus Torvalds
2019-09-15 18:32                               ` Willy Tarreau
2019-09-15 18:36                                 ` Willy Tarreau
2019-09-15 19:08                                   ` Linus Torvalds
2019-09-15 19:18                                     ` Willy Tarreau
2019-09-15 19:31                                       ` Linus Torvalds
2019-09-15 19:54                                         ` Willy Tarreau
2019-09-15 18:59                                 ` Linus Torvalds
2019-09-15 19:12                                   ` Willy Tarreau
2019-09-16  2:45                                   ` Ahmed S. Darwish
2019-09-16 18:08                               ` Lennart Poettering
2019-09-16 19:16                                 ` Willy Tarreau
2019-09-18 21:15                               ` [PATCH RFC v4 0/1] random: WARN on large getrandom() waits and introduce getrandom2() Ahmed S. Darwish
2019-09-18 21:17                                 ` [PATCH RFC v4 1/1] " Ahmed S. Darwish
2019-09-18 23:57                                   ` Linus Torvalds
2019-09-19 14:34                                     ` Theodore Y. Ts'o
2019-09-19 15:20                                       ` Linus Torvalds
2019-09-19 15:50                                         ` Linus Torvalds
2019-09-20 13:13                                           ` Theodore Y. Ts'o
2019-09-19 20:04                                         ` Linus Torvalds
2019-09-19 20:45                                           ` Alexander E. Patrakov
2019-09-19 21:47                                             ` Linus Torvalds
2019-09-19 22:23                                               ` Alexander E. Patrakov
2019-09-19 23:44                                                 ` Alexander E. Patrakov
2019-09-20 13:16                                                 ` Theodore Y. Ts'o
2019-09-23 11:55                                           ` David Laight
2019-09-20 13:08                                         ` Theodore Y. Ts'o
2019-09-20 13:46                                     ` Ahmed S. Darwish
2019-09-20 14:33                                       ` Andy Lutomirski
2019-09-20 16:29                                         ` Linus Torvalds
2019-09-20 17:52                                           ` Andy Lutomirski
2019-09-20 18:09                                             ` Linus Torvalds
2019-09-20 18:16                                               ` Willy Tarreau
2019-09-20 19:12                                               ` Andy Lutomirski
2019-09-20 19:51                                                 ` Linus Torvalds
2019-09-20 20:11                                                   ` Alexander E. Patrakov
2019-09-20 20:17                                                   ` Matthew Garrett
2019-09-20 20:51                                                   ` Andy Lutomirski
2019-09-20 22:44                                                     ` Linus Torvalds
2019-09-20 23:30                                                       ` Andy Lutomirski
2019-09-21  3:05                                                         ` Willy Tarreau
2019-09-21  6:07                                               ` Florian Weimer
2019-09-23 18:33                                                 ` Andy Lutomirski
2019-09-26 21:11                                                   ` Ahmed S. Darwish
2019-09-20 18:12                                             ` Willy Tarreau
2019-09-20 19:22                                               ` Andy Lutomirski
2019-09-20 19:37                                                 ` Willy Tarreau
2019-09-20 19:52                                                   ` Andy Lutomirski
2019-09-20 20:02                                                 ` Linus Torvalds
2019-09-20 18:15                                             ` Alexander E. Patrakov
2019-09-20 18:29                                               ` Andy Lutomirski
2019-09-20 17:26                                       ` Willy Tarreau
2019-09-20 17:56                                         ` Ahmed S. Darwish
2019-09-26 20:42                                     ` [PATCH v5 0/1] random: getrandom(2): warn on large CRNG waits, introduce new flags Ahmed S. Darwish
2019-09-26 20:44                                       ` [PATCH v5 1/1] " Ahmed S. Darwish
2019-09-26 21:39                                         ` Andy Lutomirski
2019-09-28  9:30                                           ` Ahmed S. Darwish
2019-09-14 15:02                       ` Linux 5.3-rc8 Ahmed S. Darwish
2019-09-14 16:30                         ` Linus Torvalds
2019-09-14 16:35                           ` Alexander E. Patrakov
2019-09-14 16:52                             ` Linus Torvalds
2019-09-14 17:09                               ` Alexander E. Patrakov
2019-09-14 19:19                                 ` Linus Torvalds
2019-09-15  6:56                               ` Lennart Poettering
2019-09-15  7:01                                 ` Willy Tarreau
2019-09-15  7:05                                   ` Lennart Poettering
2019-09-15  7:07                                     ` Willy Tarreau
2019-09-15  8:34                                       ` Lennart Poettering
2019-09-15 17:02                                 ` Linus Torvalds
2019-09-16  3:23                                   ` Theodore Y. Ts'o
2019-09-16  3:40                                     ` Linus Torvalds
2019-09-16  3:56                                       ` Linus Torvalds
2019-09-16 17:00                                       ` Theodore Y. Ts'o
2019-09-16 17:07                                         ` Linus Torvalds
2019-09-14 21:11                           ` Ahmed S. Darwish
2019-09-14 22:05                             ` Martin Steigerwald
2019-09-14 22:24                             ` Theodore Y. Ts'o
2019-09-14 22:32                               ` Linus Torvalds
2019-09-15  1:00                                 ` Theodore Y. Ts'o
2019-09-15  1:10                                   ` Linus Torvalds
2019-09-15  2:05                                     ` Theodore Y. Ts'o
2019-09-15  2:11                                       ` Linus Torvalds
2019-09-15  6:33                                       ` Willy Tarreau
2019-09-15  6:53                                       ` Willy Tarreau
2019-09-15  6:51                           ` Lennart Poettering
2019-09-15  7:27                             ` Ahmed S. Darwish
2019-09-15  8:48                               ` Lennart Poettering
2019-09-15 16:29                             ` Linus Torvalds
2019-09-16  1:40                               ` Ahmed S. Darwish
2019-09-16  1:48                                 ` Vito Caputo
2019-09-16  2:49                                   ` Theodore Y. Ts'o
2019-09-16  4:29                                     ` Willy Tarreau
2019-09-16  5:02                                       ` Linus Torvalds
2019-09-16  6:12                                         ` Willy Tarreau
2019-09-16 16:17                                           ` Linus Torvalds
2019-09-16 17:21                                             ` Theodore Y. Ts'o
2019-09-16 17:44                                               ` Linus Torvalds
2019-09-16 17:55                                                 ` Serge Belyshev
2019-09-16 19:08                                                 ` Willy Tarreau
2019-09-16 23:02                                                 ` Matthew Garrett
2019-09-16 23:05                                                   ` Linus Torvalds
2019-09-16 23:11                                                     ` Matthew Garrett
2019-09-16 23:13                                                       ` Alexander E. Patrakov
2019-09-16 23:15                                                         ` Matthew Garrett
2019-09-16 23:18                                                       ` Linus Torvalds
2019-09-16 23:29                                                         ` Ahmed S. Darwish
2019-09-17  1:05                                                           ` Linus Torvalds
2019-09-17  1:23                                                             ` Matthew Garrett
2019-09-17  1:41                                                               ` Linus Torvalds
2019-09-17  1:46                                                                 ` Matthew Garrett
2019-09-17  5:24                                                                   ` Willy Tarreau
2019-09-17  7:33                                                                     ` Martin Steigerwald
2019-09-17  8:35                                                                       ` Willy Tarreau
2019-09-17  8:44                                                                         ` Martin Steigerwald
2019-09-17 12:11                                                                       ` Theodore Y. Ts'o
2019-09-17 12:30                                                                         ` Ahmed S. Darwish
2019-09-17 12:46                                                                           ` Alexander E. Patrakov
2019-09-17 12:47                                                                           ` Willy Tarreau
2019-09-17 16:08                                                                           ` Lennart Poettering
2019-09-17 16:23                                                                             ` Linus Torvalds
2019-09-17 16:34                                                                               ` Reindl Harald
2019-09-17 17:42                                                                               ` Lennart Poettering
2019-09-17 18:01                                                                                 ` Linus Torvalds
2019-09-17 20:28                                                                                   ` Martin Steigerwald
2019-09-17 20:52                                                                                     ` Ahmed S. Darwish
2019-09-17 21:38                                                                                       ` Martin Steigerwald
2019-09-17 21:52                                                                                         ` Matthew Garrett
2019-09-17 22:10                                                                                           ` Martin Steigerwald
2019-09-18 13:53                                                                                             ` Lennart Poettering
2019-09-19  7:28                                                                                               ` Martin Steigerwald
2019-09-17 23:08                                                                                           ` Linus Torvalds
2019-09-18 13:40                                                                                         ` Lennart Poettering
2019-09-17 20:58                                                                                   ` Linus Torvalds
2019-09-18  9:33                                                                                     ` Rasmus Villemoes
2019-09-18 10:16                                                                                       ` Willy Tarreau
2019-09-18 10:25                                                                                         ` Alexander E. Patrakov
2019-09-18 10:42                                                                                           ` Willy Tarreau
2019-09-18 19:31                                                                                       ` Linus Torvalds
2019-09-18 19:56                                                                                 ` Eric W. Biederman
2019-09-18 20:13                                                                                   ` Linus Torvalds
2019-09-18 20:15                                                                                   ` Alexander E. Patrakov
2019-09-18 20:26                                                                                     ` Linus Torvalds
2019-09-18 22:12                                                                                       ` Willy Tarreau
2019-09-27 13:57                                                                                       ` Lennart Poettering
2019-09-27 15:58                                                                                         ` Linus Torvalds
2019-09-29  9:05                                                                                           ` Lennart Poettering
2019-09-17 13:11                                                                         ` Alexander E. Patrakov
2019-09-17 13:37                                                                           ` Alexander E. Patrakov
2019-09-17 15:57                                                                         ` Lennart Poettering
2019-09-17 16:21                                                                           ` Willy Tarreau
2019-09-17 17:13                                                                             ` Lennart Poettering
2019-09-17 17:29                                                                               ` Willy Tarreau
2019-09-17 20:42                                                                                 ` Martin Steigerwald
2019-09-18 13:38                                                                                 ` Lennart Poettering
2019-09-18 13:59                                                                                   ` Alexander E. Patrakov
2019-09-18 14:50                                                                                     ` Alexander E. Patrakov
2019-09-17 20:36                                                                             ` Martin Steigerwald
2019-09-17 16:27                                                                       ` Linus Torvalds
2019-09-17 16:34                                                                         ` Matthew Garrett
2019-09-17 17:16                                                                           ` Willy Tarreau
2019-09-17 17:20                                                                             ` Matthew Garrett
2019-09-17 17:23                                                                               ` Matthew Garrett
2019-09-17 17:57                                                                               ` Willy Tarreau
2019-09-17 16:58                                                                         ` Alexander E. Patrakov
2019-09-17 17:30                                                                           ` Lennart Poettering
2019-09-17 17:32                                                                             ` Willy Tarreau
2019-09-17 17:41                                                                               ` Alexander E. Patrakov
2019-09-17 17:28                                                                         ` Lennart Poettering
2019-09-17  0:03                                                         ` Matthew Garrett
2019-09-17  0:40                                                         ` Matthew Garrett
2019-09-17  7:15                                                     ` a sane approach to random numbers (was: Re: Linux 5.3-rc8) Martin Steigerwald
2019-09-16 18:00                                               ` Linux 5.3-rc8 Alexander E. Patrakov
2019-09-16 19:53                                               ` Ahmed S. Darwish
2019-09-17 15:32                                               ` Lennart Poettering
2019-09-16  3:31                                 ` Linus Torvalds
2019-09-23 20:49                           ` Pavel Machek [this message]
2019-09-14  9:25                     ` Ahmed S. Darwish
2019-09-14 16:27                       ` Theodore Y. Ts'o
2019-09-11 21:41             ` Ahmed S. Darwish
2019-09-11 22:37               ` Ahmed S. Darwish
2019-09-16  3:52           ` Herbert Xu
2019-09-16  4:21             ` Linus Torvalds
2019-09-16  4:53               ` Willy Tarreau
2019-09-10 11:56   ` Theodore Y. Ts'o
2019-09-16 10:33     ` Christoph Hellwig
2019-10-03 21:10   ` Jon Masters
2019-10-03 21:31   ` Jon Masters

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