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 0865AC433EF for ; Tue, 28 Dec 2021 15:39:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235356AbhL1PjI (ORCPT ); Tue, 28 Dec 2021 10:39:08 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43848 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235383AbhL1PjH (ORCPT ); Tue, 28 Dec 2021 10:39:07 -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 275D7C061574; Tue, 28 Dec 2021 07:39:07 -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 E45EEB81235; Tue, 28 Dec 2021 15:39:05 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0B7D7C36AE8; Tue, 28 Dec 2021 15:39:03 +0000 (UTC) Authentication-Results: smtp.kernel.org; dkim=pass (1024-bit key) header.d=zx2c4.com header.i=@zx2c4.com header.b="XG4T8d2y" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zx2c4.com; s=20210105; t=1640705942; 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=tkFDONjyW3jsTjHetcn/h7eGUvaH+cQm2fdxUe6PskQ=; b=XG4T8d2yqDJDgtfWvK1Ds3jUhW5mUi6chmlxsG7nGXgqz8mzcDxJ/Lk4Kk1YFYbrPH0eEU kQaMJQlJnm/9TuM8BrPL5LSGkiRbhzwlaVEk1rtOwiMFFpGR6YJw6UK5ZfAHijYzBtT0DI DUjR4XpjlnLoj/0dEVGsEBz3NhPMrqc= Received: by mail.zx2c4.com (ZX2C4 Mail Server) with ESMTPSA id f5901aa7 (TLSv1.3:AEAD-AES256-GCM-SHA384:256:NO); Tue, 28 Dec 2021 15:39:02 +0000 (UTC) From: "Jason A. Donenfeld" To: linux-kernel@vger.kernel.org, Dominik Brodowski , "Theodore Ts'o" , Hsin-Yi Wang , "Ivan T. Ivanov" , Ard Biesheuvel , linux-efi@vger.kernel.org Cc: "Jason A. Donenfeld" Subject: [PATCH v7 3/4] random: do not throw away excess input to crng_fast_load Date: Tue, 28 Dec 2021 16:38:25 +0100 Message-Id: <20211228153826.448805-3-Jason@zx2c4.com> In-Reply-To: <20211228153826.448805-1-Jason@zx2c4.com> References: <20211228153826.448805-1-Jason@zx2c4.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-efi@vger.kernel.org When crng_fast_load() is called by add_hwgenerator_randomness(), we currently will advance to crng_init==1 if we've acquired 64 bytes, and then throw away the rest of the buffer. This is a problem if irq randomness creates one call to crng_fast_load(), and then add_hwgenerator_randomness() gets called via EFI with 64 bytes. In that case, we'll advance to crng_init==1, but won't continue onward feeding in bytes to progress to crng_init==2. This commit fixes the issue by feeding leftover bytes into the next phase in add_hwgenerator_randomness(). Cc: Dominik Brodowski Signed-off-by: Jason A. Donenfeld --- 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 95aac486177e..020443e34603 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -919,12 +919,14 @@ 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; @@ -935,7 +937,7 @@ 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) { @@ -943,7 +945,7 @@ static int crng_fast_load(const char *cp, size_t len) crng_init = 1; pr_notice("fast init done\n"); } - return 1; + return ret; } /* @@ -1294,7 +1296,7 @@ void add_interrupt_randomness(int irq) 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; } @@ -2295,8 +2297,11 @@ 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. -- 2.34.1