From patchwork Sat Feb 5 16:01:17 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: 540412 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 59308C433FE for ; Sat, 5 Feb 2022 16:02:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1380338AbiBEQCF (ORCPT ); Sat, 5 Feb 2022 11:02:05 -0500 Received: from dfw.source.kernel.org ([139.178.84.217]:33318 "EHLO dfw.source.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1380344AbiBEQCC (ORCPT ); Sat, 5 Feb 2022 11:02:02 -0500 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 2BDF860FDB; Sat, 5 Feb 2022 16:02:02 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1AF10C340E8; Sat, 5 Feb 2022 16:02:01 +0000 (UTC) Authentication-Results: smtp.kernel.org; dkim=pass (1024-bit key) header.d=zx2c4.com header.i=@zx2c4.com header.b="jr6XJir6" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zx2c4.com; s=20210105; t=1644076920; 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=1iZx9N/3Al1BNBml4zAA68jO81KukzY4F+ZRLKcqbrk=; b=jr6XJir6XQ5ZoiiH2CzPV8NaiwSHZvSh16ANfTq/okBhTT1NDgBtkRLbydE9pKB3lzFCdB Wp6EFE4KRJKhXu2IL/nhWD6O1Y9yrJzPcZG+oZUwDis2RJSUVIhVpv0E82FZAGSzgPNe24 fVYB2/Cs3Po7d8QLAJtBFDk0hJuCfms= Received: by mail.zx2c4.com (ZX2C4 Mail Server) with ESMTPSA id bff21410 (TLSv1.3:AEAD-AES256-GCM-SHA384:256:NO); Sat, 5 Feb 2022 16:02:00 +0000 (UTC) From: "Jason A. Donenfeld" To: linux-kernel@vger.kernel.org, linux-crypto@vger.kernel.org Cc: "Jason A. Donenfeld" , Eric Biggers , Theodore Ts'o , Dominik Brodowski Subject: [PATCH v3 4/5] random: always wake up entropy writers after extraction Date: Sat, 5 Feb 2022 17:01:17 +0100 Message-Id: <20220205160118.252698-5-Jason@zx2c4.com> In-Reply-To: <20220205160118.252698-1-Jason@zx2c4.com> References: <20220205160118.252698-1-Jason@zx2c4.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-crypto@vger.kernel.org Now that POOL_BITS == POOL_MIN_BITS, we must unconditionally wake up entropy writers after every extraction. Therefore there's no point of write_wakeup_threshold, so we can move it to the dustbin of unused compatibility sysctls. While we're at it, we can fix a small comparison where we were waking up after <= min rather than < min. Suggested-by: Eric Biggers Cc: Theodore Ts'o Cc: Dominik Brodowski Signed-off-by: Jason A. Donenfeld --- drivers/char/random.c | 35 ++++++++++++----------------------- 1 file changed, 12 insertions(+), 23 deletions(-) diff --git a/drivers/char/random.c b/drivers/char/random.c index d0ec8503941e..82ec3a0399fb 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -296,12 +296,6 @@ enum { */ static DECLARE_WAIT_QUEUE_HEAD(random_write_wait); static struct fasync_struct *fasync; -/* - * If the entropy count falls under this number of bits, then we - * should wake up processes which are selecting or polling on write - * access to /dev/random. - */ -static int random_write_wakeup_bits = POOL_MIN_BITS; static DEFINE_SPINLOCK(random_ready_list_lock); static LIST_HEAD(random_ready_list); @@ -739,10 +733,8 @@ static void crng_reseed(struct crng_state *crng) return; } while (cmpxchg(&input_pool.entropy_count, entropy_count, 0) != entropy_count); extract_entropy(buf.key, sizeof(buf.key)); - if (random_write_wakeup_bits) { - wake_up_interruptible(&random_write_wait); - kill_fasync(&fasync, SIGIO, POLL_OUT); - } + 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, @@ -1471,7 +1463,7 @@ static __poll_t random_poll(struct file *file, poll_table *wait) mask = 0; if (crng_ready()) mask |= EPOLLIN | EPOLLRDNORM; - if (input_pool.entropy_count < random_write_wakeup_bits) + if (input_pool.entropy_count < POOL_MIN_BITS) mask |= EPOLLOUT | EPOLLWRNORM; return mask; } @@ -1556,7 +1548,7 @@ static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg) */ if (!capable(CAP_SYS_ADMIN)) return -EPERM; - if (xchg(&input_pool.entropy_count, 0) && random_write_wakeup_bits) { + if (xchg(&input_pool.entropy_count, 0)) { wake_up_interruptible(&random_write_wait); kill_fasync(&fasync, SIGIO, POLL_OUT); } @@ -1636,9 +1628,9 @@ SYSCALL_DEFINE3(getrandom, char __user *, buf, size_t, count, unsigned int, #include -static int min_write_thresh; -static int max_write_thresh = POOL_BITS; static int random_min_urandom_seed = 60; +static int random_write_wakeup_bits = POOL_MIN_BITS; +static int sysctl_poolsize = POOL_BITS; static char sysctl_bootid[16]; /* @@ -1677,7 +1669,6 @@ static int proc_do_uuid(struct ctl_table *table, int write, void *buffer, return proc_dostring(&fake_table, write, buffer, lenp, ppos); } -static int sysctl_poolsize = POOL_BITS; static struct ctl_table random_table[] = { { .procname = "poolsize", @@ -1697,10 +1688,8 @@ static struct ctl_table random_table[] = { .procname = "write_wakeup_threshold", .data = &random_write_wakeup_bits, .maxlen = sizeof(int), - .mode = 0644, - .proc_handler = proc_dointvec_minmax, - .extra1 = &min_write_thresh, - .extra2 = &max_write_thresh, + .mode = 0444, + .proc_handler = proc_dointvec, }, { .procname = "urandom_min_reseed_secs", @@ -1892,13 +1881,13 @@ void add_hwgenerator_randomness(const char *buffer, size_t count, } /* Throttle writing if we're above the trickle threshold. - * We'll be woken up again once below random_write_wakeup_thresh, - * when the calling thread is about to terminate, or once - * CRNG_RESEED_INTERVAL has lapsed. + * We'll be woken up again once below POOL_MIN_BITS, when + * the calling thread is about to terminate, or once + * CRNG_RESEED_INTERVAL has elapsed. */ wait_event_interruptible_timeout(random_write_wait, !system_wq || kthread_should_stop() || - input_pool.entropy_count <= random_write_wakeup_bits, + input_pool.entropy_count < POOL_MIN_BITS, CRNG_RESEED_INTERVAL); mix_pool_bytes(buffer, count); credit_entropy_bits(entropy);