linux-kernel - [PATCH 5.4 115/240] random: make consistent usage of crng

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Date:   Mon, 20 Jun 2022 14:50:16 +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, Theodore Tso <tytso@....edu>,
        Dominik Brodowski <linux@...inikbrodowski.net>,
        "Jason A. Donenfeld" <Jason@...c4.com>
Subject: [PATCH 5.4 115/240] random: make consistent usage of crng_ready()

From: "Jason A. Donenfeld" <Jason@...c4.com>

commit a96cfe2d427064325ecbf56df8816c6b871ec285 upstream.

Rather than sometimes checking `crng_init < 2`, we should always use the
crng_ready() macro, so that should we change anything later, it's
consistent. Additionally, that macro already has a likely() around it,
which means we don't need to open code our own likely() and unlikely()
annotations.

Cc: Theodore Ts'o <tytso@....edu>
Reviewed-by: Dominik Brodowski <linux@...inikbrodowski.net>
Signed-off-by: Jason A. Donenfeld <Jason@...c4.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/char/random.c |   19 +++++++------------
 1 file changed, 7 insertions(+), 12 deletions(-)

--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -125,18 +125,13 @@ static void try_to_generate_entropy(void
  */
 int wait_for_random_bytes(void)
 {
-	if (likely(crng_ready()))
-		return 0;
-
-	do {
+	while (!crng_ready()) {
 		int ret;
 		ret = wait_event_interruptible_timeout(crng_init_wait, crng_ready(), HZ);
 		if (ret)
 			return ret > 0 ? 0 : ret;
-
 		try_to_generate_entropy();
-	} while (!crng_ready());
-
+	}
 	return 0;
 }
 EXPORT_SYMBOL(wait_for_random_bytes);
@@ -291,7 +286,7 @@ static void crng_reseed(void)
 		++next_gen;
 	WRITE_ONCE(base_crng.generation, next_gen);
 	WRITE_ONCE(base_crng.birth, jiffies);
-	if (crng_init < 2) {
+	if (!crng_ready()) {
 		crng_init = 2;
 		finalize_init = true;
 	}
@@ -359,7 +354,7 @@ static void crng_make_state(u32 chacha_s
 	 * ready, we do fast key erasure with the base_crng directly, because
 	 * this is what crng_pre_init_inject() mutates during early init.
 	 */
-	if (unlikely(!crng_ready())) {
+	if (!crng_ready()) {
 		bool ready;
 
 		spin_lock_irqsave(&base_crng.lock, flags);
@@ -799,7 +794,7 @@ static void credit_entropy_bits(size_t n
 		entropy_count = min_t(unsigned int, POOL_BITS, orig + add);
 	} while (cmpxchg(&input_pool.entropy_count, orig, entropy_count) != orig);
 
-	if (crng_init < 2 && entropy_count >= POOL_MIN_BITS)
+	if (!crng_ready() && entropy_count >= POOL_MIN_BITS)
 		crng_reseed();
 }
 
@@ -956,7 +951,7 @@ int __init rand_initialize(void)
 	extract_entropy(base_crng.key, sizeof(base_crng.key));
 	++base_crng.generation;
 
-	if (arch_init && trust_cpu && crng_init < 2) {
+	if (arch_init && trust_cpu && !crng_ready()) {
 		crng_init = 2;
 		pr_notice("crng init done (trusting CPU's manufacturer)\n");
 	}
@@ -1545,7 +1540,7 @@ static long random_ioctl(struct file *f,
 	case RNDRESEEDCRNG:
 		if (!capable(CAP_SYS_ADMIN))
 			return -EPERM;
-		if (crng_init < 2)
+		if (!crng_ready())
 			return -ENODATA;
 		crng_reseed();
 		return 0;