linux-kernel - Re: Linux messages full of `random: get_random

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Message-ID: <20180429224928.teg6zyfjxndbcnsn@sultan-box>
Date:   Sun, 29 Apr 2018 15:49:28 -0700
From:   Sultan Alsawaf <sultanxda@...il.com>
To:     "Jason A. Donenfeld" <Jason@...c4.com>
Cc:     "Theodore Y. Ts'o" <tytso@....edu>, Pavel Machek <pavel@....cz>,
        LKML <linux-kernel@...r.kernel.org>, Jann Horn <jannh@...gle.com>
Subject: Re: Linux messages full of `random: get_random_u32 called from`

On Mon, Apr 30, 2018 at 12:43:48AM +0200, Jason A. Donenfeld wrote:
> > -       if ((fast_pool->count < 64) &&
> > -           !time_after(now, fast_pool->last + HZ))
> > -               return;
> > -
> 
> I suspect you still want the rate-limiting in place. But if you _do_
> want to cheat like this, you could instead just modify the condition
> to only relax the rate limiting when !crng_init().

Good idea. Attached a new patch that's less intrusive. It still fixes my issue,
of course.

Sultan

>From 6870b0383b88438d842599aa8608a260e6fb0ed2 Mon Sep 17 00:00:00 2001
From: Sultan Alsawaf <sultanxda@...il.com>
Date: Sun, 29 Apr 2018 15:44:27 -0700
Subject: [PATCH] random: don't ratelimit add_interrupt_randomness() until crng
 is ready

---
 drivers/char/random.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/char/random.c b/drivers/char/random.c
index 38729baed6ee..8c00c008e797 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -1201,7 +1201,7 @@ void add_interrupt_randomness(int irq, int irq_flags)
 	}
 
 	if ((fast_pool->count < 64) &&
-	    !time_after(now, fast_pool->last + HZ))
+	    !time_after(now, fast_pool->last + HZ) && crng_ready())
 		return;
 
 	r = &input_pool;
-- 
2.14.1