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 82E9FCCA480 for ; Mon, 20 Jun 2022 13:36:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1346667AbiFTNgB (ORCPT ); Mon, 20 Jun 2022 09:36:01 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33220 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1345799AbiFTNee (ORCPT ); Mon, 20 Jun 2022 09:34:34 -0400 Received: from sin.source.kernel.org (sin.source.kernel.org [IPv6:2604:1380:40e1:4800::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AEC1E27CC4; Mon, 20 Jun 2022 06:13:32 -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 sin.source.kernel.org (Postfix) with ESMTPS id 6628ACE139A; Mon, 20 Jun 2022 13:12:25 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 30F1CC3411C; Mon, 20 Jun 2022 13:12:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1655730743; bh=YTcOURT67RliY+onoFdF4rJ3Bag8bxdtEdjdRn02ukk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=URGAAWdsTKak3JcTGTXOQm/t3ZNP3Thv+kP6UHnn6FIIPG9Pb9ErXJYGWvZJh/RtQ YNnasu/rG3uOvhndqTRsdXNR8VAVCJd0rhKirpCHtNWKJz1H323cFz9Yl6CyJ2rEmB 2LcWTsmMVnlvmBk3USNLCRhT81WVb8GeIwke0VnI= 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 5.4 042/240] random: mix bootloader randomness into pool Date: Mon, 20 Jun 2022 14:49:03 +0200 Message-Id: <20220620124739.210208937@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 57826feeedb63b091f807ba8325d736775d39afd upstream. If we're trusting bootloader randomness, crng_fast_load() is called by add_hwgenerator_randomness(), which sets us to crng_init==1. However, usually it is only called once for an initial 64-byte push, so bootloader entropy will not mix any bytes into the input pool. So it's conceivable that crng_init==1 when crng_initialize_primary() is called later, but then the input pool is empty. When that happens, the crng state key will be overwritten with extracted output from the empty input pool. That's bad. In contrast, if we're not trusting bootloader randomness, we call crng_slow_load() *and* we call mix_pool_bytes(), so that later crng_initialize_primary() isn't drawing on nothing. In order to prevent crng_initialize_primary() from extracting an empty pool, have the trusted bootloader case mirror that of the untrusted bootloader case, mixing the input into the pool. [linux@dominikbrodowski.net: rewrite commit message] Signed-off-by: Dominik Brodowski Signed-off-by: Jason A. Donenfeld Signed-off-by: Greg Kroah-Hartman --- drivers/char/random.c | 1 + 1 file changed, 1 insertion(+) --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -2299,6 +2299,7 @@ void add_hwgenerator_randomness(const ch if (unlikely(crng_init == 0)) { size_t ret = crng_fast_load(buffer, count); + mix_pool_bytes(poolp, buffer, ret); count -= ret; buffer += ret; if (!count || crng_init == 0)