linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: "Jason A. Donenfeld" <Jason@zx2c4.com>
To: linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org
Cc: tytso@mit.edu, linux@dominikbrodowski.net, ebiggers@kernel.org,
	"Jason A. Donenfeld" <Jason@zx2c4.com>,
	Eric Biggers <ebiggers@google.com>
Subject: [PATCH v2 6/9] random: absorb fast pool into input pool after fast load
Date: Wed,  9 Feb 2022 02:19:16 +0100	[thread overview]
Message-ID: <20220209011919.493762-7-Jason@zx2c4.com> (raw)
In-Reply-To: <20220209011919.493762-1-Jason@zx2c4.com>

During crng_init == 0, we never credit entropy in add_interrupt_
randomness(), but instead dump it directly into the base_crng. That's
fine, except for the fact that we then wind up throwing away that
entropy later when we switch to extracting from the input pool and
overwriting the base_crng key. The two other early init sites --
add_hwgenerator_randomness()'s use crng_fast_load() and add_device_
randomness()'s use of crng_slow_load() -- always additionally give their
inputs to the input pool. But not add_interrupt_randomness().

This commit fixes that shortcoming by calling mix_pool_bytes() after
crng_fast_load() in add_interrupt_randomness(). That's partially
verboten on PREEMPT_RT, where it implies taking spinlock_t from an IRQ
handler. But this also only happens during early boot and then never
again after that. Should this turn into a larger problem later for some
esoteric reason, we can always use `if (IS_ENABLED(PREEMPT_RT))` or
something similar to that. But for now, this should do.

Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Dominik Brodowski <linux@dominikbrodowski.net>
Suggested-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
---
 drivers/char/random.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/char/random.c b/drivers/char/random.c
index 785a4545c9d7..20374bce9a07 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -864,6 +864,13 @@ void add_interrupt_randomness(int irq)
 		    crng_fast_load((u8 *)fast_pool->pool, sizeof(fast_pool->pool)) > 0) {
 			fast_pool->count = 0;
 			fast_pool->last = now;
+
+			/* Technically this call means that we're using a spinlock_t
+			 * in the IRQ handler, which isn't terrific for PREEMPT_RT.
+			 * However, this only happens during very early boot, and then
+			 * never again, so we live with it.
+			 */
+			mix_pool_bytes(&fast_pool->pool, sizeof(fast_pool->pool));
 		}
 		return;
 	}
-- 
2.35.0


  parent reply	other threads:[~2022-02-09  2:42 UTC|newest]

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-02-09  1:19 [PATCH v2 0/9] random: cleanups around per-cpu crng & rdrand Jason A. Donenfeld
2022-02-09  1:19 ` [PATCH v2 1/9] random: use RDSEED instead of RDRAND in entropy extraction Jason A. Donenfeld
2022-02-09  6:18   ` Dominik Brodowski
2022-02-09  1:19 ` [PATCH v2 2/9] random: get rid of secondary crngs Jason A. Donenfeld
2022-02-09  8:22   ` Dominik Brodowski
2022-02-09 10:26     ` Jason A. Donenfeld
2022-02-21  2:38   ` Eric Biggers
2022-02-09  1:19 ` [PATCH v2 3/9] random: inline leaves of rand_initialize() Jason A. Donenfeld
2022-02-09  8:22   ` Dominik Brodowski
2022-02-09 10:27     ` Jason A. Donenfeld
2022-02-09  1:19 ` [PATCH v2 4/9] random: ensure early RDSEED goes through mixer on init Jason A. Donenfeld
2022-02-09  8:23   ` Dominik Brodowski
2022-02-09 10:37     ` Jason A. Donenfeld
2022-02-09  1:19 ` [PATCH v2 5/9] random: do not xor RDRAND when writing into /dev/random Jason A. Donenfeld
2022-02-09  8:28   ` Dominik Brodowski
2022-02-09 10:40     ` Jason A. Donenfeld
2022-02-09  1:19 ` Jason A. Donenfeld [this message]
2022-02-09  8:29   ` [PATCH v2 6/9] random: absorb fast pool into input pool after fast load Dominik Brodowski
2022-02-09 10:45     ` Jason A. Donenfeld
2022-02-15 21:13       ` [PATCH v3] " Jason A. Donenfeld
2022-02-21  2:47         ` Eric Biggers
2022-02-21 14:57           ` Jason A. Donenfeld
2022-02-21 14:58             ` [PATCH v4] " Jason A. Donenfeld
2022-02-21 19:08               ` Eric Biggers
2022-02-09  1:19 ` [PATCH v2 7/9] random: use simpler fast key erasure flow on per-cpu keys Jason A. Donenfeld
2022-02-09  8:30   ` Dominik Brodowski
2022-02-09 10:54     ` Jason A. Donenfeld
2022-02-14 18:46   ` [PATCH v3] " Jason A. Donenfeld
2022-02-16 23:21     ` [PATCH v4] " Jason A. Donenfeld
2022-02-21  3:37       ` Eric Biggers
2022-02-21 14:42         ` Jason A. Donenfeld
2022-02-09  1:19 ` [PATCH v2 8/9] random: use hash function for crng_slow_load() Jason A. Donenfeld
2022-02-09  8:30   ` Dominik Brodowski
2022-02-21  3:40   ` Eric Biggers
2022-02-09  1:19 ` [PATCH v2 9/9] random: remove outdated INT_MAX >> 6 check in urandom_read() Jason A. Donenfeld
2022-02-21  3:56   ` Eric Biggers

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=20220209011919.493762-7-Jason@zx2c4.com \
    --to=jason@zx2c4.com \
    --cc=ebiggers@google.com \
    --cc=ebiggers@kernel.org \
    --cc=linux-crypto@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux@dominikbrodowski.net \
    --cc=tytso@mit.edu \
    /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).