From patchwork Tue Feb 8 15:53:30 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Jason A. Donenfeld" X-Patchwork-Id: 540853 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 AEE3BC433FE for ; Tue, 8 Feb 2022 15:54:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233501AbiBHPyD (ORCPT ); Tue, 8 Feb 2022 10:54:03 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35132 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1382085AbiBHPyB (ORCPT ); Tue, 8 Feb 2022 10:54:01 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id F199DC0613CB; Tue, 8 Feb 2022 07:54:00 -0800 (PST) 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 dfw.source.kernel.org (Postfix) with ESMTPS id 8FDF36166C; Tue, 8 Feb 2022 15:54:00 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9129AC340EF; Tue, 8 Feb 2022 15:53:59 +0000 (UTC) Authentication-Results: smtp.kernel.org; dkim=pass (1024-bit key) header.d=zx2c4.com header.i=@zx2c4.com header.b="oKDfgIZ+" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zx2c4.com; s=20210105; t=1644335638; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=o+To7SbPAC6WHaVLqmEB9nPHSa7awDbf9XLlklQoFXk=; b=oKDfgIZ+GJWbJ/eZs0Xc1AdVS4TscsyaS017EOeG0O/3kwp2nqM8WPRN/eKGvkdO1aTlOa vPMehcnXlLau25TmVMG33P7/8yMs52rCfhx0nSbiNVZW87oH+e0488wHNhUJZYDHKOEfA5 rVy6U0Xo7dc/KvMHSvPtFPa1IADWi9s= Received: by mail.zx2c4.com (ZX2C4 Mail Server) with ESMTPSA id 0b957a98 (TLSv1.3:AEAD-AES256-GCM-SHA384:256:NO); Tue, 8 Feb 2022 15:53:58 +0000 (UTC) From: "Jason A. Donenfeld" To: linux-kernel@vger.kernel.org, linux-crypto@vger.kernel.org Cc: "Jason A. Donenfeld" , Theodore Ts'o , Dominik Brodowski Subject: [PATCH v1 2/7] random: get rid of secondary crngs Date: Tue, 8 Feb 2022 16:53:30 +0100 Message-Id: <20220208155335.378318-3-Jason@zx2c4.com> In-Reply-To: <20220208155335.378318-1-Jason@zx2c4.com> References: <20220208155335.378318-1-Jason@zx2c4.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-crypto@vger.kernel.org As the comment said, this is indeed a "hack". Since it was introduced, it's been a constant state machine nightmare, with lots of subtle early boot issues and a wildly complex set of machinery to keep everything in sync. Rather than continuing to play whack-a-mole with this approach, this commit simply removes it entirely. This commit is preparation for "random: use simpler fast key erasure flow on per-cpu keys" in this series, which introduces a simpler (and faster) mechanism to accomplish the same thing. Cc: Theodore Ts'o Cc: Dominik Brodowski Signed-off-by: Jason A. Donenfeld --- drivers/char/random.c | 225 ++++++++++-------------------------------- 1 file changed, 53 insertions(+), 172 deletions(-) diff --git a/drivers/char/random.c b/drivers/char/random.c index 42a3a3663767..59d8d38f6a07 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -323,14 +323,11 @@ static struct crng_state primary_crng = { * its value (from 0->1->2). */ static int crng_init = 0; -static bool crng_need_final_init = false; #define crng_ready() (likely(crng_init > 1)) static int crng_init_cnt = 0; -static unsigned long crng_global_init_time = 0; #define CRNG_INIT_CNT_THRESH (2 * CHACHA_KEY_SIZE) -static void _extract_crng(struct crng_state *crng, u8 out[CHACHA_BLOCK_SIZE]); -static void _crng_backtrack_protect(struct crng_state *crng, - u8 tmp[CHACHA_BLOCK_SIZE], int used); +static void extract_crng(u8 out[CHACHA_BLOCK_SIZE]); +static void crng_backtrack_protect(u8 tmp[CHACHA_BLOCK_SIZE], int used); static void process_random_ready_list(void); static void _get_random_bytes(void *buf, int nbytes); @@ -365,7 +362,7 @@ static struct { static void extract_entropy(void *buf, size_t nbytes); -static void crng_reseed(struct crng_state *crng); +static void crng_reseed(void); /* * This function adds bytes into the entropy "pool". It does not @@ -459,7 +456,7 @@ static void credit_entropy_bits(int nbits) trace_credit_entropy_bits(nbits, entropy_count, _RET_IP_); if (crng_init < 2 && entropy_count >= POOL_MIN_BITS) - crng_reseed(&primary_crng); + crng_reseed(); } /********************************************************************* @@ -472,16 +469,7 @@ static void credit_entropy_bits(int nbits) static DECLARE_WAIT_QUEUE_HEAD(crng_init_wait); -/* - * Hack to deal with crazy userspace progams when they are all trying - * to access /dev/urandom in parallel. The programs are almost - * certainly doing something terribly wrong, but we'll work around - * their brain damage. - */ -static struct crng_state **crng_node_pool __read_mostly; - static void invalidate_batched_entropy(void); -static void numa_crng_init(void); static bool trust_cpu __ro_after_init = IS_ENABLED(CONFIG_RANDOM_TRUST_CPU); static int __init parse_trust_cpu(char *arg) @@ -490,24 +478,6 @@ static int __init parse_trust_cpu(char *arg) } early_param("random.trust_cpu", parse_trust_cpu); -static bool crng_init_try_arch(struct crng_state *crng) -{ - int i; - bool arch_init = true; - unsigned long rv; - - for (i = 4; i < 16; i++) { - if (!arch_get_random_seed_long(&rv) && - !arch_get_random_long(&rv)) { - rv = random_get_entropy(); - arch_init = false; - } - crng->state[i] ^= rv; - } - - return arch_init; -} - static bool __init crng_init_try_arch_early(void) { int i; @@ -526,100 +496,17 @@ static bool __init crng_init_try_arch_early(void) return arch_init; } -static void crng_initialize_secondary(struct crng_state *crng) -{ - chacha_init_consts(crng->state); - _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(void) +static void __init crng_initialize(void) { extract_entropy(&primary_crng.state[4], sizeof(u32) * 12); if (crng_init_try_arch_early() && trust_cpu && crng_init < 2) { invalidate_batched_entropy(); - numa_crng_init(); crng_init = 2; pr_notice("crng init done (trusting CPU's manufacturer)\n"); } primary_crng.init_time = jiffies - CRNG_RESEED_INTERVAL - 1; } -static void crng_finalize_init(void) -{ - if (!system_wq) { - /* We can't call numa_crng_init until we have workqueues, - * so mark this for processing later. */ - crng_need_final_init = true; - return; - } - - invalidate_batched_entropy(); - numa_crng_init(); - crng_init = 2; - crng_need_final_init = false; - process_random_ready_list(); - wake_up_interruptible(&crng_init_wait); - kill_fasync(&fasync, SIGIO, POLL_IN); - pr_notice("crng init done\n"); - if (unseeded_warning.missed) { - pr_notice("%d get_random_xx warning(s) missed due to ratelimiting\n", - unseeded_warning.missed); - unseeded_warning.missed = 0; - } - if (urandom_warning.missed) { - pr_notice("%d urandom warning(s) missed due to ratelimiting\n", - urandom_warning.missed); - urandom_warning.missed = 0; - } -} - -static void do_numa_crng_init(struct work_struct *work) -{ - int i; - struct crng_state *crng; - struct crng_state **pool; - - pool = kcalloc(nr_node_ids, sizeof(*pool), GFP_KERNEL | __GFP_NOFAIL); - for_each_online_node(i) { - crng = kmalloc_node(sizeof(struct crng_state), - GFP_KERNEL | __GFP_NOFAIL, i); - spin_lock_init(&crng->lock); - crng_initialize_secondary(crng); - pool[i] = crng; - } - /* pairs with READ_ONCE() in select_crng() */ - if (cmpxchg_release(&crng_node_pool, NULL, pool) != NULL) { - for_each_node(i) - kfree(pool[i]); - kfree(pool); - } -} - -static DECLARE_WORK(numa_crng_init_work, do_numa_crng_init); - -static void numa_crng_init(void) -{ - if (IS_ENABLED(CONFIG_NUMA)) - schedule_work(&numa_crng_init_work); -} - -static struct crng_state *select_crng(void) -{ - if (IS_ENABLED(CONFIG_NUMA)) { - struct crng_state **pool; - int nid = numa_node_id(); - - /* pairs with cmpxchg_release() in do_numa_crng_init() */ - pool = READ_ONCE(crng_node_pool); - if (pool && pool[nid]) - return pool[nid]; - } - - return &primary_crng; -} - /* * crng_fast_load() can be called by code in the interrupt service * path. So we can't afford to dilly-dally. Returns the number of @@ -697,68 +584,71 @@ static int crng_slow_load(const u8 *cp, size_t len) return 1; } -static void crng_reseed(struct crng_state *crng) +static void crng_reseed(void) { unsigned long flags; - int i; + int i, entropy_count; union { u8 block[CHACHA_BLOCK_SIZE]; u32 key[8]; } buf; - if (crng == &primary_crng) { - int entropy_count; - do { - entropy_count = READ_ONCE(input_pool.entropy_count); - if (entropy_count < POOL_MIN_BITS) - return; - } while (cmpxchg(&input_pool.entropy_count, entropy_count, 0) != entropy_count); - extract_entropy(buf.key, sizeof(buf.key)); - wake_up_interruptible(&random_write_wait); - kill_fasync(&fasync, SIGIO, POLL_OUT); - } else { - _extract_crng(&primary_crng, buf.block); - _crng_backtrack_protect(&primary_crng, buf.block, - CHACHA_KEY_SIZE); - } - spin_lock_irqsave(&crng->lock, flags); + do { + entropy_count = READ_ONCE(input_pool.entropy_count); + if (entropy_count < POOL_MIN_BITS) + return; + } while (cmpxchg(&input_pool.entropy_count, entropy_count, 0) != entropy_count); + extract_entropy(buf.key, sizeof(buf.key)); + wake_up_interruptible(&random_write_wait); + kill_fasync(&fasync, SIGIO, POLL_OUT); + + spin_lock_irqsave(&primary_crng.lock, flags); for (i = 0; i < 8; i++) - crng->state[i + 4] ^= buf.key[i]; + primary_crng.state[i + 4] ^= buf.key[i]; memzero_explicit(&buf, sizeof(buf)); - WRITE_ONCE(crng->init_time, jiffies); - spin_unlock_irqrestore(&crng->lock, flags); - if (crng == &primary_crng && crng_init < 2) - crng_finalize_init(); + WRITE_ONCE(primary_crng.init_time, jiffies); + spin_unlock_irqrestore(&primary_crng.lock, flags); + if (crng_init < 2) { + invalidate_batched_entropy(); + crng_init = 2; + process_random_ready_list(); + wake_up_interruptible(&crng_init_wait); + kill_fasync(&fasync, SIGIO, POLL_IN); + pr_notice("crng init done\n"); + if (unseeded_warning.missed) { + pr_notice("%d get_random_xx warning(s) missed due to ratelimiting\n", + unseeded_warning.missed); + unseeded_warning.missed = 0; + } + if (urandom_warning.missed) { + pr_notice("%d urandom warning(s) missed due to ratelimiting\n", + urandom_warning.missed); + urandom_warning.missed = 0; + } + } } -static void _extract_crng(struct crng_state *crng, u8 out[CHACHA_BLOCK_SIZE]) +static void extract_crng(u8 out[CHACHA_BLOCK_SIZE]) { unsigned long flags, init_time; if (crng_ready()) { - init_time = READ_ONCE(crng->init_time); - if (time_after(READ_ONCE(crng_global_init_time), init_time) || - time_after(jiffies, init_time + CRNG_RESEED_INTERVAL)) - crng_reseed(crng); + init_time = READ_ONCE(primary_crng.init_time); + if (time_after(jiffies, init_time + CRNG_RESEED_INTERVAL)) + crng_reseed(); } - spin_lock_irqsave(&crng->lock, flags); - chacha20_block(&crng->state[0], out); - if (crng->state[12] == 0) - crng->state[13]++; - spin_unlock_irqrestore(&crng->lock, flags); -} - -static void extract_crng(u8 out[CHACHA_BLOCK_SIZE]) -{ - _extract_crng(select_crng(), out); + spin_lock_irqsave(&primary_crng.lock, flags); + chacha20_block(&primary_crng.state[0], out); + if (primary_crng.state[12] == 0) + primary_crng.state[13]++; + spin_unlock_irqrestore(&primary_crng.lock, flags); } /* * Use the leftover bytes from the CRNG block output (if there is * enough) to mutate the CRNG key to provide backtracking protection. */ -static void _crng_backtrack_protect(struct crng_state *crng, - u8 tmp[CHACHA_BLOCK_SIZE], int used) +static void crng_backtrack_protect(u8 tmp[CHACHA_BLOCK_SIZE], int used) { unsigned long flags; u32 *s, *d; @@ -769,17 +659,12 @@ static void _crng_backtrack_protect(struct crng_state *crng, extract_crng(tmp); used = 0; } - spin_lock_irqsave(&crng->lock, flags); + spin_lock_irqsave(&primary_crng.lock, flags); s = (u32 *)&tmp[used]; - d = &crng->state[4]; + d = &primary_crng.state[4]; for (i = 0; i < 8; i++) *d++ ^= *s++; - spin_unlock_irqrestore(&crng->lock, flags); -} - -static void crng_backtrack_protect(u8 tmp[CHACHA_BLOCK_SIZE], int used) -{ - _crng_backtrack_protect(select_crng(), tmp, used); + spin_unlock_irqrestore(&primary_crng.lock, flags); } static ssize_t extract_crng_user(void __user *buf, size_t nbytes) @@ -1381,10 +1266,7 @@ static void __init init_std_data(void) int __init rand_initialize(void) { init_std_data(); - if (crng_need_final_init) - crng_finalize_init(); - crng_initialize_primary(); - crng_global_init_time = jiffies; + crng_initialize(); if (ratelimit_disable) { urandom_warning.interval = 0; unseeded_warning.interval = 0; @@ -1554,8 +1436,7 @@ static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg) return -EPERM; if (crng_init < 2) return -ENODATA; - crng_reseed(&primary_crng); - WRITE_ONCE(crng_global_init_time, jiffies - 1); + crng_reseed(); return 0; default: return -EINVAL;