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 3FF3DC43334 for ; Mon, 20 Jun 2022 13:50:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S244163AbiFTNuT (ORCPT ); Mon, 20 Jun 2022 09:50:19 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55978 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1349197AbiFTNsb (ORCPT ); Mon, 20 Jun 2022 09:48:31 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1097C2F03B; Mon, 20 Jun 2022 06:17:47 -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 ams.source.kernel.org (Postfix) with ESMTPS id 427A8B811C6; Mon, 20 Jun 2022 13:16:26 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8DBFAC3411B; Mon, 20 Jun 2022 13:16:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1655730985; bh=kLu6oEFnz7kWzqySjKoPppP6306WDVKu2D0M9xJxpzc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=eDa9nYR2rklghfW4NFDB2DRU1lmpfU47m5lotZyGzXqqXMlH+a0uNYYpeL+C7RuEz sQJlT2QYBa9ijqDKBoadRxzYREndaTZupTRPZoF0CZ248gHFzMKcErUv0mASNZ7mKv 1VPuQ0YUmBDlMUXfNX+C5acDLmt32vH90Zi/9YyM= 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 5.4 118/240] random: skip fast_init if hwrng provides large chunk of entropy Date: Mon, 20 Jun 2022 14:50:19 +0200 Message-Id: <20220620124742.432273887@linuxfoundation.org> X-Mailer: git-send-email 2.36.1 In-Reply-To: <20220620124737.799371052@linuxfoundation.org> References: <20220620124737.799371052@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: stable@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 @@ -1120,7 +1120,7 @@ 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;