From: "Ahmed S. Darwish" <darwish.07@gmail.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: "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: Re: Linux 5.3-rc8
Date: Sat, 14 Sep 2019 17:02:06 +0200 [thread overview]
Message-ID: <20190914150206.GA2270@darwi-home-pc> (raw)
In-Reply-To: <CAHk-=wjyH910+JRBdZf_Y9G54c1M=LBF8NKXB6vJcm9XjLnRfg@mail.gmail.com>
On Thu, Sep 12, 2019 at 12:34:45PM +0100, Linus Torvalds wrote:
> On Thu, Sep 12, 2019 at 9:25 AM Theodore Y. Ts'o <tytso@mit.edu> wrote:
> >
> > Hmm, one thought might be GRND_FAILSAFE, which will wait up to two
> > minutes before returning "best efforts" randomness and issuing a huge
> > massive warning if it is triggered?
>
> Yeah, based on (by now) _years_ of experience with people mis-using
> "get me random numbers", I think the sense of a new flag needs to be
> "yeah, I'm willing to wait for it".
>
> Because most people just don't want to wait for it, and most people
> don't think about it, and we need to make the default be for that
> "don't think about it" crowd, with the people who ask for randomness
> sources for a secure key having to very clearly and very explicitly
> say "Yes, I understand that this can take minutes and can only be done
> long after boot".
>
> Even then people will screw that up because they copy code, or some
> less than gifted rodent writes a library and decides "my library is so
> important that I need that waiting sooper-sekrit-secure random
> number", and then people use that broken library by mistake without
> realizing that it's not going to be reliable at boot time.
>
> An alternative might be to make getrandom() just return an error
> instead of waiting. Sure, fill the buffer with "as random as we can"
> stuff, but then return -EINVAL because you called us too early.
>
ACK, that's probably _the_ most sensible approach. Only caveat is
the slight change in user-space API semantics though...
For example, this breaks the just released systemd-random-seed(8)
as it _explicitly_ requests blocking behvior from getrandom() here:
=> 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 */
}
if (k < 0) {
log_debug_errno(errno, "Failed to read random data with "
"getrandom(), falling back to "
"/dev/urandom: %m");
} else if ((size_t) k < buf_size) {
log_debug("Short read from getrandom(), falling back to "
"/dev/urandom: %m");
} else {
getrandom_worked = true;
}
Nonetheless, a slightly broken systemd-random-seed, that was just
released only 11 days ago (v243), is honestly much better than a
*non-booting system*...
I've sent an RFC patch at [1].
To handle the systemd case, I'll add the discussed "yeah, I'm
willing to wait for it" flag (GRND_BLOCK) in v2.
If this whole approach is going to be merged, and the slight ABI
breakage is to be tolerated (hmmmmm?), I wonder how will systemd
random-seed handle the semantics change though without doing
ugly kernel version checks..
thanks,
[1] https://lkml.kernel.org/r/20190914122500.GA1425@darwi-home-pc
--
darwi
http://darwish.chasingpointers.com
next prev parent reply other threads:[~2019-09-14 15:02 UTC|newest]
Thread overview: 213+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-08 20:59 Linux 5.3-rc8 Linus Torvalds
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
2019-09-20 0:51 ` [random] ec47a799bf: WARNING:at_drivers/char/random.c:#getrandom_wait kernel test robot
2019-09-14 15:02 ` Ahmed S. Darwish [this message]
2019-09-14 16:30 ` Linux 5.3-rc8 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 ` chaos generating driver was " Pavel Machek
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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20190914150206.GA2270@darwi-home-pc \
--to=darwish.07@gmail.com \
--cc=adilger.kernel@dilger.ca \
--cc=jack@suse.cz \
--cc=lennart@poettering.net \
--cc=linux-ext4@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mccann@jhu.edu \
--cc=patrakov@gmail.com \
--cc=rstrode@redhat.com \
--cc=torvalds@linux-foundation.org \
--cc=tytso@mit.edu \
--cc=zachary@baishancloud.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).