Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.debian.bugs.dist > #896635

Bug#897572: urandom hang in early boot

From Ben Caradoc-Davies <ben@transient.nz>
Newsgroups linux.debian.bugs.dist, linux.debian.kernel
Subject Bug#897572: urandom hang in early boot
Date 2018-05-08 06:00 +0200
Message-ID <vN1Xc-25k-7@gated-at.bofh.it> (permalink)
References (3 earlier) <vLbR0-2oY-1@gated-at.bofh.it> <vMXAe-7Xs-5@gated-at.bofh.it> <vN0eJ-19n-1@gated-at.bofh.it> <vLbR0-2oY-1@gated-at.bofh.it> <vN0eJ-19n-1@gated-at.bofh.it>
Organization linux.* mail to news gateway

Cross-posted to 2 groups.

Show all headers | View raw

On 08/05/18 14:00, Ben Hutchings wrote:
> You keep saying this, but based on my reading of the code I don't see
> how reads from /dev/urandom can end up blocking.

Ben, I think you are right. I have picked through the code in detail and 
none of the changes affect any substantive logic (except logging). I do 
not think urandom_read can ever block. The urandom warning may be from a 
previous read before the hang: related, but a red herring.

The *one* substantive change that is affected is getrandom:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/char/random.c#n2007

If something calls getrandom without GRND_NONBLOCK while crng_init==1 
(during early boot):

- Before 43838a23a05f ("random: fix crng_ready() test"), this just falls 
thorough to urandom_read and everything seems to work (but is not 
cryptographically secure).

- After 43838a23a05f ("random: fix crng_ready() test"), this will call 
wait_for_random_bytes and hang waiting on mouse wiggles 
(cryptographically secure).

But what is calling getrandom without GRND_NONBLOCK? I could find 
nothing in the plymouth or systemd/udev codebase. Or is it something 
they spawn? I even read the plymouth softwaves.script.

Kind regards,

-- 
Ben Caradoc-Davies <ben@transient.nz>
Director
Transient Software Limited <https://transient.nz/>
New Zealand

Back to linux.debian.bugs.dist | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

Bug#897572: linux-image-4.16.0-1-amd64 breaks plymouth LUKS prompt (missing Kaby Lake firmware?) Ben Caradoc-Davies <ben@transient.nz> - 2018-05-03 04:10 +0200
  Bug#897572: linux-image-4.16.0-1-amd64 breaks plymouth LUKS prompt Ben Caradoc-Davies <ben@transient.nz> - 2018-05-03 06:50 +0200
  Bug#897572: linux-image-4.16.0-1-amd64 breaks plymouth LUKS prompt Ben Caradoc-Davies <ben@transient.nz> - 2018-05-03 07:30 +0200
  Bug#897572: linux-image-4.16.0-1-amd64 breaks plymouth LUKS prompt Ben Caradoc-Davies <ben@transient.nz> - 2018-05-03 07:40 +0200
    Bug#897572: linux-image-4.16.0-1-amd64 breaks plymouth LUKS prompt Ben Caradoc-Davies <ben@transient.nz> - 2018-05-04 01:40 +0200
    Bug#897572: linux-image-4.16.0-1-amd64 breaks plymouth LUKS prompt Ben Caradoc-Davies <ben@transient.nz> - 2018-05-04 02:00 +0200
  Bug#897572: linux-image-4.16.0-1-amd64 breaks plymouth LUKS prompt Ben Hutchings <ben@decadent.org.uk> - 2018-05-05 21:10 +0200
    Bug#897572: linux-image-4.16.0-1-amd64 breaks plymouth LUKS prompt Ben Caradoc-Davies <ben@transient.nz> - 2018-05-06 02:40 +0200
      Bug#897572: linux-image-4.16.0-1-amd64 breaks plymouth LUKS prompt Ben Hutchings <ben@decadent.org.uk> - 2018-05-06 05:10 +0200
    Bug#897572: linux-image-4.16.0-1-amd64 breaks plymouth LUKS prompt Laurent Bigonville <bigon@debian.org> - 2018-05-06 17:30 +0200
      Bug#897572: linux-image-4.16.0-1-amd64 breaks plymouth LUKS prompt Ben Hutchings <ben@decadent.org.uk> - 2018-05-06 19:50 +0200
  Bug#897572: plymouth: long delay before splashscreen with kernel 4.16 Ben Caradoc-Davies <ben@transient.nz> - 2018-05-06 03:10 +0200
    Bug#897958: plymouth: long delay before splashscreen with kernel 4.16 Arnaud Meyer <arnaudmeyer@gmx.com> - 2018-05-06 05:30 +0200
    Bug#897572: plymouth: long delay before splashscreen with kernel 4.16 at46 <at46n@t-online.de> - 2018-05-06 08:50 +0200
      Bug#897572: plymouth: long delay before splashscreen with kernel 4.16 Ben Caradoc-Davies <ben@transient.nz> - 2018-05-07 02:50 +0200
        Bug#897958: plymouth: long delay before splashscreen with kernel 4.16 Ben Caradoc-Davies <ben@transient.nz> - 2018-05-07 04:10 +0200
  Bug#897572:  Eric Mill <eric@konklone.com> - 2018-05-06 19:30 +0200
  Bug#897572: [PATCH] Revert "random: fix crng_ready() test" Ben Caradoc-Davies <ben@transient.nz> - 2018-05-07 05:10 +0200
    Bug#897572: [PATCH] Revert "random: fix crng_ready() test" "Theodore Y. Ts'o" <tytso@mit.edu> - 2018-05-07 06:20 +0200
  Bug#897572: [PATCH] Revert "random: fix crng_ready() test" Ben Caradoc-Davies <ben@transient.nz> - 2018-05-07 05:50 +0200
    Bug#897572: [PATCH] Revert "random: fix crng_ready() test" "Theodore Y. Ts'o" <tytso@mit.edu> - 2018-05-07 06:20 +0200
  Bug#897572: urandom hang in early boot Laurent Bigonville <bigon@debian.org> - 2018-05-07 19:40 +0200
    Bug#897572: urandom hang in early boot Ben Caradoc-Davies <ben@transient.nz> - 2018-05-08 01:20 +0200
      Bug#897572: urandom hang in early boot Ben Hutchings <ben@decadent.org.uk> - 2018-05-08 04:10 +0200
        Bug#897572: urandom hang in early boot Ben Caradoc-Davies <ben@transient.nz> - 2018-05-08 06:00 +0200
          Bug#897572: urandom hang in early boot Ben Caradoc-Davies <ben@transient.nz> - 2018-05-08 07:00 +0200
  Bug#897572: urandom hang in early boot Bjørn Mork <bjorn@mork.no> - 2018-05-08 13:40 +0200
    Bug#897572: urandom hang in early boot Yves-Alexis Perez <corsac@debian.org> - 2018-05-09 18:40 +0200
  Bug#897572: getrandom hang in early boot prevents plymouth passphrase entry Esokrates <esokrarkose@gmail.com> - 2018-05-09 11:00 +0200
  Bug#897572: [PATCH] Copy fontconfig .uuid files to avoid getrandom hang in early boot Ben Caradoc-Davies <ben@transient.nz> - 2018-05-10 02:00 +0200
    Bug#897572: [PATCH] Copy fontconfig .uuid files to avoid getrandom hang in early boot Laurent Bigonville <bigon@debian.org> - 2018-05-14 10:30 +0200
      Bug#897572: [PATCH] Copy fontconfig .uuid files to avoid getrandom hang in early boot Ben Caradoc-Davies <ben@transient.nz> - 2018-05-15 08:00 +0200
  Bug#897572: getrandom hang in early boot prevents plymouth passphrase entry Ben Caradoc-Davies <ben@transient.nz> - 2018-05-10 02:50 +0200
    Bug#897572: getrandom hang in early boot prevents plymouth passphrase entry "Theodore Y. Ts'o" <tytso@mit.edu> - 2018-05-10 04:00 +0200
      Bug#897572: getrandom hang in early boot prevents plymouth passphrase entry Ben Caradoc-Davies <ben@transient.nz> - 2018-05-10 04:40 +0200
        Bug#897572: getrandom hang in early boot prevents plymouth passphrase entry Laurent Bigonville <bigon@debian.org> - 2018-05-10 11:50 +0200
        Bug#897572: getrandom hang in early boot prevents plymouth passphrase entry Yves-Alexis Perez <corsac@debian.org> - 2018-05-10 12:50 +0200

csiph-web