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 29D0EC433F5 for ; Fri, 27 May 2022 11:54:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231267AbiE0Lyq (ORCPT ); Fri, 27 May 2022 07:54:46 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41934 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1352421AbiE0LuY (ORCPT ); Fri, 27 May 2022 07:50:24 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6461814E2F8; Fri, 27 May 2022 04:44:35 -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 dfw.source.kernel.org (Postfix) with ESMTPS id B7BD061D52; Fri, 27 May 2022 11:44:34 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id C6E29C385A9; Fri, 27 May 2022 11:44:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1653651874; bh=a9XVNqU5sn7bRAO9DMP0qktS82o+XYBC9OPCV8lHv6w=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=PF3GWdDkHinKGbcZsXjKlLMDgkTU3JVobTqPLDKhjBZB93IbgU7XQzBjxmPu7zeQ8 HXMtWFj3PWTnuKpu9DKnjZtcy25zXFokm0ljCY83rU4/NGvh47F/z3SNrMly10BsJL V3ycGEZvMic6em6WuciegcNXFqZaxK3X+YN7c5do= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Theodore Tso , Eric Biggers , Eric Biggers , Dominik Brodowski , "Jason A. Donenfeld" Subject: [PATCH 5.10 059/163] random: always wake up entropy writers after extraction Date: Fri, 27 May 2022 10:48:59 +0200 Message-Id: <20220527084836.307932306@linuxfoundation.org> X-Mailer: git-send-email 2.36.1 In-Reply-To: <20220527084828.156494029@linuxfoundation.org> References: <20220527084828.156494029@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 489c7fc44b5740d377e8cfdbf0851036e493af00 upstream. 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. Cc: Theodore Ts'o Suggested-by: Eric Biggers Reviewed-by: Eric Biggers Reviewed-by: Dominik Brodowski Signed-off-by: Jason A. Donenfeld Signed-off-by: Greg Kroah-Hartman --- Documentation/admin-guide/sysctl/kernel.rst | 7 ++++- drivers/char/random.c | 33 +++++++++------------------- 2 files changed, 16 insertions(+), 24 deletions(-) --- a/Documentation/admin-guide/sysctl/kernel.rst +++ b/Documentation/admin-guide/sysctl/kernel.rst @@ -1011,14 +1011,17 @@ This is a directory, with the following * ``poolsize``: the entropy pool size, in bits; * ``urandom_min_reseed_secs``: obsolete (used to determine the minimum - number of seconds between urandom pool reseeding). + number of seconds between urandom pool reseeding). This file is + writable for compatibility purposes, but writing to it has no effect + on any RNG behavior. * ``uuid``: a UUID generated every time this is retrieved (this can thus be used to generate UUIDs at will); * ``write_wakeup_threshold``: when the entropy count drops below this (as a number of bits), processes waiting to write to ``/dev/random`` - are woken up. + are woken up. This file is writable for compatibility purposes, but + writing to it has no effect on any RNG behavior. If ``drivers/char/random.c`` is built with ``ADD_INTERRUPT_BENCH`` defined, these additional entries are present: --- 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_stat 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 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, */ 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 * #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 return proc_dostring(&fake_table, write, buffer, lenp, ppos); } -static int sysctl_poolsize = POOL_BITS; extern struct ctl_table random_table[]; struct ctl_table random_table[] = { { @@ -1699,9 +1690,7 @@ struct ctl_table random_table[] = { .data = &random_write_wakeup_bits, .maxlen = sizeof(int), .mode = 0644, - .proc_handler = proc_dointvec_minmax, - .extra1 = &min_write_thresh, - .extra2 = &max_write_thresh, + .proc_handler = proc_dointvec, }, { .procname = "urandom_min_reseed_secs", @@ -1882,13 +1871,13 @@ void add_hwgenerator_randomness(const ch } /* 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);