From nobody Fri Dec 19 17:15:00 2025 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 F2760FA373E for ; Mon, 24 Oct 2022 11:46:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231536AbiJXLp5 (ORCPT ); Mon, 24 Oct 2022 07:45:57 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40036 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231668AbiJXLoO (ORCPT ); Mon, 24 Oct 2022 07:44:14 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 29CBA73C1F; Mon, 24 Oct 2022 04:41:24 -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 BF2D561281; Mon, 24 Oct 2022 11:39:54 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id D21C4C43144; Mon, 24 Oct 2022 11:39:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1666611594; bh=pmOPmI+oMzt7p797XAEtSZK+rbfd/3Vbxj8UdGQP6Ek=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ohjFe7wJsIa4OHcGfJetr0J3szMfO934pBpJHdoKdKRsCMX3KUOYGM2i7106j/54b nlKS18/x3p+tYn4vtXztiqvj3yC5CiE2KMgBosUQWulBlqm8levNMQ+g2SYqKgLcsl 0JDMFPjQXNzVUcddzRYv51RazcQPRhiSHbQGmWIw= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Guozihua , Zhongguohua , Al Viro , Theodore Tso , Andrew Lutomirski , "Jason A. Donenfeld" Subject: [PATCH 4.9 037/159] random: restore O_NONBLOCK support Date: Mon, 24 Oct 2022 13:29:51 +0200 Message-Id: <20221024112950.742291077@linuxfoundation.org> X-Mailer: git-send-email 2.38.1 In-Reply-To: <20221024112949.358278806@linuxfoundation.org> References: <20221024112949.358278806@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" From: Jason A. Donenfeld 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 Signed-off-by: Greg Kroah-Hartman --- drivers/char/random.c | 4 ++++ 1 file changed, 4 insertions(+) --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -1295,6 +1295,10 @@ static ssize_t random_read_iter(struct k { int ret; =20 + if (!crng_ready() && + (kiocb->ki_filp->f_flags & O_NONBLOCK)) + return -EAGAIN; + ret =3D wait_for_random_bytes(); if (ret !=3D 0) return ret;