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
next prev 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
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