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 B3C76C433F5 for ; Fri, 27 May 2022 12:07:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S244683AbiE0MEl (ORCPT ); Fri, 27 May 2022 08:04:41 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54616 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1353061AbiE0L4J (ORCPT ); Fri, 27 May 2022 07:56:09 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6F0DE14B66E; Fri, 27 May 2022 04:49:39 -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 0476C61D56; Fri, 27 May 2022 11:49:39 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0DBE2C385A9; Fri, 27 May 2022 11:49:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1653652178; bh=S4lomHdt9VVKtYuHtfMgqi4J2P/Uz5hhKmPw0PTyM/0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=auqEvqR4fFGSYg+X3lqhHzukPFZC/vTleVhzM8j6X2bTViHZC5KSAY7YeB0qwkWXW wB3d16VKSdTw9zKBTq1/c8EIgFbqyegoOXQ+64r0UxoNQQQ6T7LwM7v7XuLK05bUfF 0AvQ/HWINW4xbk/3NRkR+fNHfLt2bhRA5TuJlRqQ= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Dominik Brodowski , "Jason A. Donenfeld" Subject: [PATCH 5.10 109/163] random: skip fast_init if hwrng provides large chunk of entropy Date: Fri, 27 May 2022 10:49:49 +0200 Message-Id: <20220527084843.357363195@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 af704c856e888fb044b058d731d61b46eeec499d upstream. At boot time, EFI calls add_bootloader_randomness(), which in turn calls add_hwgenerator_randomness(). Currently add_hwgenerator_randomness() feeds the first 64 bytes of randomness to the "fast init" non-crypto-grade phase. But if add_hwgenerator_randomness() gets called with more than POOL_MIN_BITS of entropy, there's no point in passing it off to the "fast init" stage, since that's enough entropy to bootstrap the real RNG. The "fast init" stage is just there to provide _something_ in the case where we don't have enough entropy to properly bootstrap the RNG. But if we do have enough entropy to bootstrap the RNG, the current logic doesn't serve a purpose. So, in the case where we're passed greater than or equal to POOL_MIN_BITS of entropy, this commit makes us skip the "fast init" phase. Cc: Dominik Brodowski Signed-off-by: Jason A. Donenfeld Signed-off-by: Greg Kroah-Hartman --- drivers/char/random.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -1125,7 +1125,7 @@ void rand_initialize_disk(struct gendisk void add_hwgenerator_randomness(const void *buffer, size_t count, size_t entropy) { - if (unlikely(crng_init == 0)) { + if (unlikely(crng_init == 0 && entropy < POOL_MIN_BITS)) { size_t ret = crng_pre_init_inject(buffer, count, true); mix_pool_bytes(buffer, ret); count -= ret;