From patchwork Mon Jan 24 18:42:50 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 535633 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 39BF4C433EF for ; Mon, 24 Jan 2022 21:05:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1353115AbiAXVET (ORCPT ); Mon, 24 Jan 2022 16:04:19 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45218 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1443078AbiAXU7O (ORCPT ); Mon, 24 Jan 2022 15:59:14 -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 51869C04D627; Mon, 24 Jan 2022 12:01:25 -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 E574460B43; Mon, 24 Jan 2022 20:01:24 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A6C15C340E5; Mon, 24 Jan 2022 20:01:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1643054484; bh=/dGnbHoEWV8PzqxzFoRe3cgvni4WisFgqP4qPwYHDpw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=YDlhHVbNZ42gp5XFIA7LjLDvDABtD0wVrknDrfFjCRiT9EkW3x/FXXDpCXiffpN7+ DPRRbCIaFfzxSVXc/kxE6xKCTY8pXOxWBMp811fv8IbAolaeXkLheClTLF6q140oi+ 2mRXJleyhIHlHbL/SzDyoSLhH47aZdfmd15c3OZk= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Dominik Brodowski , "Jason A. Donenfeld" , Sasha Levin Subject: [PATCH 5.10 405/563] random: do not throw away excess input to crng_fast_load Date: Mon, 24 Jan 2022 19:42:50 +0100 Message-Id: <20220124184038.450540055@linuxfoundation.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20220124184024.407936072@linuxfoundation.org> References: <20220124184024.407936072@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Jason A. Donenfeld [ Upstream commit 73c7733f122e8d0107f88655a12011f68f69e74b ] When crng_fast_load() is called by add_hwgenerator_randomness(), we currently will advance to crng_init==1 once we've acquired 64 bytes, and then throw away the rest of the buffer. Usually, that is not a problem: When add_hwgenerator_randomness() gets called via EFI or DT during setup_arch(), there won't be any IRQ randomness. Therefore, the 64 bytes passed by EFI exactly matches what is needed to advance to crng_init==1. Usually, DT seems to pass 64 bytes as well -- with one notable exception being kexec, which hands over 128 bytes of entropy to the kexec'd kernel. In that case, we'll advance to crng_init==1 once 64 of those bytes are consumed by crng_fast_load(), but won't continue onward feeding in bytes to progress to crng_init==2. This commit fixes the issue by feeding any leftover bytes into the next phase in add_hwgenerator_randomness(). [linux@dominikbrodowski.net: rewrite commit message] Signed-off-by: Dominik Brodowski Signed-off-by: Jason A. Donenfeld Signed-off-by: Sasha Levin --- drivers/char/random.c | 19 ++++++++++++------- 1 file changed, 12 insertions(+), 7 deletions(-) diff --git a/drivers/char/random.c b/drivers/char/random.c index 8c94380e7a463..5444206f35e22 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -922,12 +922,14 @@ static struct crng_state *select_crng(void) /* * crng_fast_load() can be called by code in the interrupt service - * path. So we can't afford to dilly-dally. + * path. So we can't afford to dilly-dally. Returns the number of + * bytes processed from cp. */ -static int crng_fast_load(const char *cp, size_t len) +static size_t crng_fast_load(const char *cp, size_t len) { unsigned long flags; char *p; + size_t ret = 0; if (!spin_trylock_irqsave(&primary_crng.lock, flags)) return 0; @@ -938,7 +940,7 @@ static int crng_fast_load(const char *cp, size_t len) p = (unsigned char *) &primary_crng.state[4]; while (len > 0 && crng_init_cnt < CRNG_INIT_CNT_THRESH) { p[crng_init_cnt % CHACHA_KEY_SIZE] ^= *cp; - cp++; crng_init_cnt++; len--; + cp++; crng_init_cnt++; len--; ret++; } spin_unlock_irqrestore(&primary_crng.lock, flags); if (crng_init_cnt >= CRNG_INIT_CNT_THRESH) { @@ -946,7 +948,7 @@ static int crng_fast_load(const char *cp, size_t len) crng_init = 1; pr_notice("fast init done\n"); } - return 1; + return ret; } /* @@ -1299,7 +1301,7 @@ void add_interrupt_randomness(int irq, int irq_flags) if (unlikely(crng_init == 0)) { if ((fast_pool->count >= 64) && crng_fast_load((char *) fast_pool->pool, - sizeof(fast_pool->pool))) { + sizeof(fast_pool->pool)) > 0) { fast_pool->count = 0; fast_pool->last = now; } @@ -2319,8 +2321,11 @@ void add_hwgenerator_randomness(const char *buffer, size_t count, struct entropy_store *poolp = &input_pool; if (unlikely(crng_init == 0)) { - crng_fast_load(buffer, count); - return; + size_t ret = crng_fast_load(buffer, count); + count -= ret; + buffer += ret; + if (!count || crng_init == 0) + return; } /* Suspend writing if we're above the trickle threshold.