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 8E84EC433EF for ; Fri, 14 Jan 2022 08:27:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239791AbiANI1K (ORCPT ); Fri, 14 Jan 2022 03:27:10 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50426 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241014AbiANIY7 (ORCPT ); Fri, 14 Jan 2022 03:24:59 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EC628C06136C; Fri, 14 Jan 2022 00:23:30 -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 ams.source.kernel.org (Postfix) with ESMTPS id A98D8B823E6; Fri, 14 Jan 2022 08:23:29 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A5AB9C36AE9; Fri, 14 Jan 2022 08:23:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1642148608; bh=8iKIb85u6ipfes5d+CNyFzUf/X0fNPURJcuud1v18+U=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=cCb2VyrBmhM0miAhX500sLOVA7XABXDjYIKDIgtUqjTSu68ukjCkmcijgacLKaVXr 4C2Hfov6Vl7EX71XLKABxkLHDbsgQ/vK6+t+HO3cX/+EuWF65rlPSoisl8bSblMkWM cMUjyWYo4dAgzUia900nMtKpsq8YN/kkWFpvD4XU= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, "Ivan T. Ivanov" , Dominik Brodowski , "Jason A. Donenfeld" Subject: [PATCH 5.16 32/37] random: fix crash on multiple early calls to add_bootloader_randomness() Date: Fri, 14 Jan 2022 09:16:46 +0100 Message-Id: <20220114081545.895319224@linuxfoundation.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20220114081544.849748488@linuxfoundation.org> References: <20220114081544.849748488@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: Dominik Brodowski commit f7e67b8e803185d0aabe7f29d25a35c8be724a78 upstream. Currently, if CONFIG_RANDOM_TRUST_BOOTLOADER is enabled, multiple calls to add_bootloader_randomness() are broken and can cause a NULL pointer dereference, as noted by Ivan T. Ivanov. This is not only a hypothetical problem, as qemu on arm64 may provide bootloader entropy via EFI and via devicetree. On the first call to add_hwgenerator_randomness(), crng_fast_load() is executed, and if the seed is long enough, crng_init will be set to 1. On subsequent calls to add_bootloader_randomness() and then to add_hwgenerator_randomness(), crng_fast_load() will be skipped. Instead, wait_event_interruptible() and then credit_entropy_bits() will be called. If the entropy count for that second seed is large enough, that proceeds to crng_reseed(). However, both wait_event_interruptible() and crng_reseed() depends (at least in numa_crng_init()) on workqueues. Therefore, test whether system_wq is already initialized, which is a sufficient indicator that workqueue_init_early() has progressed far enough. If we wind up hitting the !system_wq case, we later want to do what would have been done there when wqs are up, so set a flag, and do that work later from the rand_initialize() call. Reported-by: Ivan T. Ivanov Fixes: 18b915ac6b0a ("efi/random: Treat EFI_RNG_PROTOCOL output as bootloader randomness") Cc: stable@vger.kernel.org Signed-off-by: Dominik Brodowski [Jason: added crng_need_done state and related logic.] Signed-off-by: Jason A. Donenfeld Signed-off-by: Greg Kroah-Hartman --- drivers/char/random.c | 56 ++++++++++++++++++++++++++++++++------------------ 1 file changed, 36 insertions(+), 20 deletions(-) --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -461,6 +461,7 @@ 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; @@ -828,6 +829,36 @@ static void __init crng_initialize_prima crng->init_time = jiffies - CRNG_RESEED_INTERVAL - 1; } +static void crng_finalize_init(struct crng_state *crng) +{ + if (crng != &primary_crng || crng_init >= 2) + return; + 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; + 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; + } +} + #ifdef CONFIG_NUMA static void do_numa_crng_init(struct work_struct *work) { @@ -982,25 +1013,7 @@ static void crng_reseed(struct crng_stat memzero_explicit(&buf, sizeof(buf)); WRITE_ONCE(crng->init_time, jiffies); spin_unlock_irqrestore(&crng->lock, flags); - if (crng == &primary_crng && crng_init < 2) { - invalidate_batched_entropy(); - numa_crng_init(); - 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; - } - } + crng_finalize_init(crng); } static void _extract_crng(struct crng_state *crng, @@ -1780,6 +1793,8 @@ static void __init init_std_data(struct int __init rand_initialize(void) { init_std_data(&input_pool); + if (crng_need_final_init) + crng_finalize_init(&primary_crng); crng_initialize_primary(&primary_crng); crng_global_init_time = jiffies; if (ratelimit_disable) { @@ -2288,7 +2303,8 @@ void add_hwgenerator_randomness(const ch * We'll be woken up again once below random_write_wakeup_thresh, * or when the calling thread is about to terminate. */ - wait_event_interruptible(random_write_wait, kthread_should_stop() || + wait_event_interruptible(random_write_wait, + !system_wq || kthread_should_stop() || ENTROPY_BITS(&input_pool) <= random_write_wakeup_bits); mix_pool_bytes(poolp, buffer, count); credit_entropy_bits(poolp, entropy);