From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 86749C4167D for ; Fri, 27 May 2022 12:17:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1353587AbiE0MPb (ORCPT ); Fri, 27 May 2022 08:15:31 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49906 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1352776AbiE0MA4 (ORCPT ); Fri, 27 May 2022 08:00:56 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 538483969E; Fri, 27 May 2022 04:52:51 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 95300B824DA; Fri, 27 May 2022 11:52:49 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id E59D4C36AF7; Fri, 27 May 2022 11:52:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1653652368; bh=6szvqkdjoU+O8bp4LyOclQVEm9CULO8mYqsEvKUxCeE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=SAhVPuwr1fvve/Iri12uj+cFHZkGIMS2m1tyW42zPWNKkIYEpGVB5XEwnjB6WfJtj tXi3vn/ReCC82ZU8slse9CQOIFRH9tpItJGQ6+uKVBjhtPcRF41achlIFwaYX4NID7 nE3BQxKyHqpGSJ7oSbupNHwjh0I9WhTwr5ZHz3Hw= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Dominik Brodowski , Joe Perches , "Jason A. Donenfeld" Subject: [PATCH 5.15 127/145] random: use symbolic constants for crng_init states Date: Fri, 27 May 2022 10:50:28 +0200 Message-Id: <20220527084905.925492255@linuxfoundation.org> X-Mailer: git-send-email 2.36.1 In-Reply-To: <20220527084850.364560116@linuxfoundation.org> References: <20220527084850.364560116@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "Jason A. Donenfeld" commit e3d2c5e79a999aa4e7d6f0127e16d3da5a4ff70d upstream. crng_init represents a state machine, with three states, and various rules for transitions. For the longest time, we've been managing these with "0", "1", and "2", and expecting people to figure it out. To make the code more obvious, replace these with proper enum values representing the transition, and then redocument what each of these states mean. Reviewed-by: Dominik Brodowski Cc: Joe Perches Signed-off-by: Jason A. Donenfeld Signed-off-by: Greg Kroah-Hartman --- drivers/char/random.c | 38 +++++++++++++++++++------------------- 1 file changed, 19 insertions(+), 19 deletions(-) --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -70,16 +70,16 @@ *********************************************************************/ /* - * crng_init = 0 --> Uninitialized - * 1 --> Initialized - * 2 --> Initialized from input_pool - * * crng_init is protected by base_crng->lock, and only increases - * its value (from 0->1->2). + * its value (from empty->early->ready). */ -static int crng_init = 0; -#define crng_ready() (likely(crng_init > 1)) -/* Various types of waiters for crng_init->2 transition. */ +static enum { + CRNG_EMPTY = 0, /* Little to no entropy collected */ + CRNG_EARLY = 1, /* At least POOL_EARLY_BITS collected */ + CRNG_READY = 2 /* Fully initialized with POOL_READY_BITS collected */ +} crng_init = CRNG_EMPTY; +#define crng_ready() (likely(crng_init >= CRNG_READY)) +/* Various types of waiters for crng_init->CRNG_READY transition. */ static DECLARE_WAIT_QUEUE_HEAD(crng_init_wait); static struct fasync_struct *fasync; static DEFINE_SPINLOCK(random_ready_chain_lock); @@ -284,7 +284,7 @@ static void crng_reseed(void) WRITE_ONCE(base_crng.generation, next_gen); WRITE_ONCE(base_crng.birth, jiffies); if (!crng_ready()) { - crng_init = 2; + crng_init = CRNG_READY; finalize_init = true; } spin_unlock_irqrestore(&base_crng.lock, flags); @@ -378,7 +378,7 @@ static void crng_make_state(u32 chacha_s * For the fast path, we check whether we're ready, unlocked first, and * then re-check once locked later. In the case where we're really not * ready, we do fast key erasure with the base_crng directly, extracting - * when crng_init==0. + * when crng_init is CRNG_EMPTY. */ if (!crng_ready()) { bool ready; @@ -386,7 +386,7 @@ static void crng_make_state(u32 chacha_s spin_lock_irqsave(&base_crng.lock, flags); ready = crng_ready(); if (!ready) { - if (crng_init == 0) + if (crng_init == CRNG_EMPTY) extract_entropy(base_crng.key, sizeof(base_crng.key)); crng_fast_key_erasure(base_crng.key, chacha_state, random_data, random_data_len); @@ -740,8 +740,8 @@ EXPORT_SYMBOL(get_random_bytes_arch); enum { POOL_BITS = BLAKE2S_HASH_SIZE * 8, - POOL_INIT_BITS = POOL_BITS, /* No point in settling for less. */ - POOL_FAST_INIT_BITS = POOL_INIT_BITS / 2 + POOL_READY_BITS = POOL_BITS, /* When crng_init->CRNG_READY */ + POOL_EARLY_BITS = POOL_READY_BITS / 2 /* When crng_init->CRNG_EARLY */ }; static struct { @@ -836,13 +836,13 @@ static void credit_init_bits(size_t nbit init_bits = min_t(unsigned int, POOL_BITS, orig + add); } while (cmpxchg(&input_pool.init_bits, orig, init_bits) != orig); - if (!crng_ready() && init_bits >= POOL_INIT_BITS) + if (!crng_ready() && init_bits >= POOL_READY_BITS) crng_reseed(); - else if (unlikely(crng_init == 0 && init_bits >= POOL_FAST_INIT_BITS)) { + else if (unlikely(crng_init == CRNG_EMPTY && init_bits >= POOL_EARLY_BITS)) { spin_lock_irqsave(&base_crng.lock, flags); - if (crng_init == 0) { + if (crng_init == CRNG_EMPTY) { extract_entropy(base_crng.key, sizeof(base_crng.key)); - crng_init = 1; + crng_init = CRNG_EARLY; } spin_unlock_irqrestore(&base_crng.lock, flags); } @@ -1517,7 +1517,7 @@ const struct file_operations urandom_fop * * - write_wakeup_threshold - the amount of entropy in the input pool * below which write polls to /dev/random will unblock, requesting - * more entropy, tied to the POOL_INIT_BITS constant. It is writable + * more entropy, tied to the POOL_READY_BITS constant. It is writable * to avoid breaking old userspaces, but writing to it does not * change any behavior of the RNG. * @@ -1532,7 +1532,7 @@ const struct file_operations urandom_fop #include static int sysctl_random_min_urandom_seed = CRNG_RESEED_INTERVAL / HZ; -static int sysctl_random_write_wakeup_bits = POOL_INIT_BITS; +static int sysctl_random_write_wakeup_bits = POOL_READY_BITS; static int sysctl_poolsize = POOL_BITS; static u8 sysctl_bootid[UUID_SIZE];