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 X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0D47FC2D0BE for ; Sun, 8 Dec 2019 13:57:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CFBF8206F4 for ; Sun, 8 Dec 2019 13:57:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726728AbfLHN5d (ORCPT ); Sun, 8 Dec 2019 08:57:33 -0500 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:60188 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726755AbfLHNym (ORCPT ); Sun, 8 Dec 2019 08:54:42 -0500 Received: from [192.168.4.242] (helo=deadeye) by shadbolt.decadent.org.uk with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.89) (envelope-from ) id 1idx1C-0007eG-ML; Sun, 08 Dec 2019 13:54:38 +0000 Received: from ben by deadeye with local (Exim 4.93-RC1) (envelope-from ) id 1idx1B-0002NI-MX; Sun, 08 Dec 2019 13:54:37 +0000 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, Denis Kirjanov , "Herbert Xu" , "Theodore Ts'o" , "Laurent Vivier" Date: Sun, 08 Dec 2019 13:53:20 +0000 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) X-Patchwork-Hint: ignore Subject: [PATCH 3.16 36/72] hwrng: core - don't wait on add_early_randomness() In-Reply-To: X-SA-Exim-Connect-IP: 192.168.4.242 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org 3.16.79-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Laurent Vivier commit 78887832e76541f77169a24ac238fccb51059b63 upstream. add_early_randomness() is called by hwrng_register() when the hardware is added. If this hardware and its module are present at boot, and if there is no data available the boot hangs until data are available and can't be interrupted. For instance, in the case of virtio-rng, in some cases the host can be not able to provide enough entropy for all the guests. We can have two easy ways to reproduce the problem but they rely on misconfiguration of the hypervisor or the egd daemon: - if virtio-rng device is configured to connect to the egd daemon of the host but when the virtio-rng driver asks for data the daemon is not connected, - if virtio-rng device is configured to connect to the egd daemon of the host but the egd daemon doesn't provide data. The guest kernel will hang at boot until the virtio-rng driver provides enough data. To avoid that, call rng_get_data() in non-blocking mode (wait=0) from add_early_randomness(). Signed-off-by: Laurent Vivier Fixes: d9e797261933 ("hwrng: add randomness to system from rng...") Reviewed-by: Theodore Ts'o Signed-off-by: Herbert Xu [bwh: Backported to 3.16: adjust context] Signed-off-by: Ben Hutchings --- drivers/char/hw_random/core.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/drivers/char/hw_random/core.c +++ b/drivers/char/hw_random/core.c @@ -68,7 +68,7 @@ static void add_early_randomness(struct int bytes_read; size_t size = min_t(size_t, 16, rng_buffer_size()); - bytes_read = rng_get_data(rng, rng_buffer, size, 1); + bytes_read = rng_get_data(rng, rng_buffer, size, 0); if (bytes_read > 0) add_device_randomness(rng_buffer, bytes_read); }