linux-kernel - [PATCH 5.4 022/240] random: split primary/secondary crng init paths

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Date:   Mon, 20 Jun 2022 14:48:43 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Mark Rutland <mark.rutland@....com>,
        Mark Brown <broonie@...nel.org>, Theodore Tso <tytso@....edu>,
        "Jason A. Donenfeld" <Jason@...c4.com>
Subject: [PATCH 5.4 022/240] random: split primary/secondary crng init paths

From: Mark Rutland <mark.rutland@....com>

commit 5cbe0f13b51ac2fb2fd55902cff8d0077fc084c0 upstream.

Currently crng_initialize() is used for both the primary CRNG and
secondary CRNGs. While we wish to share common logic, we need to do a
number of additional things for the primary CRNG, and this would be
easier to deal with were these handled in separate functions.

This patch splits crng_initialize() into crng_initialize_primary() and
crng_initialize_secondary(), with common logic factored out into a
crng_init_try_arch() helper.

There should be no functional change as a result of this patch.

Signed-off-by: Mark Rutland <mark.rutland@....com>
Cc: Mark Brown <broonie@...nel.org>
Cc: Theodore Ts'o <tytso@....edu>
Link: https://lore.kernel.org/r/20200210130015.17664-2-mark.rutland@arm.com
Signed-off-by: Theodore Ts'o <tytso@....edu>
Signed-off-by: Jason A. Donenfeld <Jason@...c4.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/char/random.c |   34 ++++++++++++++++++++++------------
 1 file changed, 22 insertions(+), 12 deletions(-)

--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -782,27 +782,37 @@ static int __init parse_trust_cpu(char *
 }
 early_param("random.trust_cpu", parse_trust_cpu);
 
-static void crng_initialize(struct crng_state *crng)
+static bool crng_init_try_arch(struct crng_state *crng)
 {
 	int		i;
-	int		arch_init = 1;
+	bool		arch_init = true;
 	unsigned long	rv;
 
-	memcpy(&crng->state[0], "expand 32-byte k", 16);
-	if (crng == &primary_crng)
-		_extract_entropy(&input_pool, &crng->state[4],
-				 sizeof(__u32) * 12, 0);
-	else
-		_get_random_bytes(&crng->state[4], sizeof(__u32) * 12);
 	for (i = 4; i < 16; i++) {
 		if (!arch_get_random_seed_long(&rv) &&
 		    !arch_get_random_long(&rv)) {
 			rv = random_get_entropy();
-			arch_init = 0;
+			arch_init = false;
 		}
 		crng->state[i] ^= rv;
 	}
-	if (trust_cpu && arch_init && crng == &primary_crng) {
+
+	return arch_init;
+}
+
+static void crng_initialize_secondary(struct crng_state *crng)
+{
+	memcpy(&crng->state[0], "expand 32-byte k", 16);
+	_get_random_bytes(&crng->state[4], sizeof(__u32) * 12);
+	crng_init_try_arch(crng);
+	crng->init_time = jiffies - CRNG_RESEED_INTERVAL - 1;
+}
+
+static void __init crng_initialize_primary(struct crng_state *crng)
+{
+	memcpy(&crng->state[0], "expand 32-byte k", 16);
+	_extract_entropy(&input_pool, &crng->state[4], sizeof(__u32) * 12, 0);
+	if (crng_init_try_arch(crng) && trust_cpu) {
 		invalidate_batched_entropy();
 		numa_crng_init();
 		crng_init = 2;
@@ -853,7 +863,7 @@ static void do_numa_crng_init(struct wor
 		crng = kmalloc_node(sizeof(struct crng_state),
 				    GFP_KERNEL | __GFP_NOFAIL, i);
 		spin_lock_init(&crng->lock);
-		crng_initialize(crng);
+		crng_initialize_secondary(crng);
 		pool[i] = crng;
 	}
 	/* pairs with READ_ONCE() in select_crng() */
@@ -1793,7 +1803,7 @@ int __init rand_initialize(void)
 	init_std_data(&input_pool);
 	if (crng_need_final_init)
 		crng_finalize_init(&primary_crng);
-	crng_initialize(&primary_crng);
+	crng_initialize_primary(&primary_crng);
 	crng_global_init_time = jiffies;
 	if (ratelimit_disable) {
 		urandom_warning.interval = 0;