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 006BDC433FE for ; Thu, 13 Oct 2022 16:32:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229640AbiJMQcn (ORCPT ); Thu, 13 Oct 2022 12:32:43 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49976 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229638AbiJMQcm (ORCPT ); Thu, 13 Oct 2022 12:32:42 -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 96A9BF034B for ; Thu, 13 Oct 2022 09:32:41 -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 51EB7B81D03 for ; Thu, 13 Oct 2022 16:32:40 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id DB2A1C433C1; Thu, 13 Oct 2022 16:32:38 +0000 (UTC) Authentication-Results: smtp.kernel.org; dkim=pass (1024-bit key) header.d=zx2c4.com header.i=@zx2c4.com header.b="mgFeMCuR" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zx2c4.com; s=20210105; t=1665678757; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=NTpFXmluGzDUwtC15aowm1eIaCthcTF7HKAB7UuvSHA=; b=mgFeMCuR99yKwY9N2yH4+qNOGQFpnEm0du9oAv/k/7G7Tyg4sF1SYl/Z0PpUoDtWH8ApK4 ZT/P5DfQa+BJbJnecaTrtMMeyGeNHhXpSw2NsyeVd8atq4vs8nEQYiTlk9Yy8+yx881Sjy ol9rGTGZJxjLjuzQKHiLSbZR1J38B18= Received: by mail.zx2c4.com (ZX2C4 Mail Server) with ESMTPSA id d3fd5a1d (TLSv1.3:TLS_AES_256_GCM_SHA384:256:NO); Thu, 13 Oct 2022 16:32:36 +0000 (UTC) From: "Jason A. Donenfeld" To: gregkh@linuxfoundation.org, stable@vger.kernel.org Cc: "Jason A. Donenfeld" Subject: [PATCH stable 4.9.y] random: restore O_NONBLOCK support Date: Thu, 13 Oct 2022 10:32:31 -0600 Message-Id: <20221013163231.1410141-1-Jason@zx2c4.com> In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org commit cd4f24ae9404fd31fc461066e57889be3b68641b upstream. Prior to 5.6, when /dev/random was opened with O_NONBLOCK, it would return -EAGAIN if there was no entropy. When the pools were unified in 5.6, this was lost. The post 5.6 behavior of blocking until the pool is initialized, and ignoring O_NONBLOCK in the process, went unnoticed, with no reports about the regression received for two and a half years. However, eventually this indeed did break somebody's userspace. So we restore the old behavior, by returning -EAGAIN if the pool is not initialized. Unlike the old /dev/random, this can only occur during early boot, after which it never blocks again. In order to make this O_NONBLOCK behavior consistent with other expectations, also respect users reading with preadv2(RWF_NOWAIT) and similar. Fixes: 30c08efec888 ("random: make /dev/random be almost like /dev/urandom") Reported-by: Guozihua Reported-by: Zhongguohua Cc: Al Viro Cc: Theodore Ts'o Cc: Andrew Lutomirski Cc: stable@vger.kernel.org Signed-off-by: Jason A. Donenfeld --- drivers/char/random.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/drivers/char/random.c b/drivers/char/random.c index 1cbc33ee5a5f..838f66723ccd 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -1295,6 +1295,10 @@ static ssize_t random_read_iter(struct kiocb *kiocb, struct iov_iter *iter) { int ret; + if (!crng_ready() && + (kiocb->ki_filp->f_flags & O_NONBLOCK)) + return -EAGAIN; + ret = wait_for_random_bytes(); if (ret != 0) return ret; -- 2.37.3