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 E3A02C433EF for ; Fri, 27 May 2022 11:41:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1351616AbiE0Ll1 (ORCPT ); Fri, 27 May 2022 07:41:27 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45714 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1351778AbiE0LkF (ORCPT ); Fri, 27 May 2022 07:40:05 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 745C5111BA6; Fri, 27 May 2022 04:39:18 -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 D82D961CB7; Fri, 27 May 2022 11:39:17 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id E75EFC385A9; Fri, 27 May 2022 11:39:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1653651557; bh=zeCNXD/6mPqe80gmC393S7dCSxWXSaOLreAdBp1vAWM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=w3hyO/5s3HTX2+ezbV1IxPIfyaIvgQh0jWUkx6xnbj3mv0vwBPMQX6iA4sxzrx+Hl hee6BzldFU8/rKFmOEG9OzeYormZu9C8NwuAQMti0JfHGvd3to4YjgvYFFvy1hYHAf +qV5J3OehherNOeq7JTmCGFboBszrNZIWJe2wfZw= 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 5.15 016/145] random: mix bootloader randomness into pool Date: Fri, 27 May 2022 10:48:37 +0200 Message-Id: <20220527084852.955822975@linuxfoundation.org> X-Mailer: git-send-email 2.36.1 In-Reply-To: <20220527084850.364560116@linuxfoundation.org> References: <20220527084850.364560116@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 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 @@ -2301,6 +2301,7 @@ 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)