From nobody Tue Jun 23 08:13:11 2026 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 E644AC433F5 for ; Tue, 8 Mar 2022 17:19:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1348879AbiCHRUX (ORCPT ); Tue, 8 Mar 2022 12:20:23 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53850 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1348898AbiCHRUN (ORCPT ); Tue, 8 Mar 2022 12:20:13 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0CECE53B51 for ; Tue, 8 Mar 2022 09:18:58 -0800 (PST) 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 14819B81B8B for ; Tue, 8 Mar 2022 17:18:57 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 59BCEC340EB; Tue, 8 Mar 2022 17:18:55 +0000 (UTC) Authentication-Results: smtp.kernel.org; dkim=pass (1024-bit key) header.d=zx2c4.com header.i=@zx2c4.com header.b="BiuKkS0j" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zx2c4.com; s=20210105; t=1646759933; 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; bh=AZ+d5tFFjQ1rNjN45rdxTOo6PPrAddVrmZAsuxSqFck=; b=BiuKkS0j8xqotj6mFNIf7r/lkKm0JyJSrUJKyckxpjJPW9FNuvEqdj3dVtHlBIFTyWo1jE P05CokGXeCz2hz5tn8XQY4UYavumtAgD8urzDuN0328r4mGvk0nj8HdfSd1PcbanRlTWGJ q/5985/J7MGtA/X2b/IlMbHQIiGyAwQ= Received: by mail.zx2c4.com (ZX2C4 Mail Server) with ESMTPSA id dfec7c9e (TLSv1.3:AEAD-AES256-GCM-SHA384:256:NO); Tue, 8 Mar 2022 17:18:53 +0000 (UTC) From: "Jason A. Donenfeld" To: linux-kernel@vger.kernel.org Cc: "Jason A. Donenfeld" , Dominik Brodowski , Theodore Ts'o Subject: [PATCH] random: check for signal and try earlier when generating entropy Date: Tue, 8 Mar 2022 10:18:49 -0700 Message-Id: <20220308171849.242534-1-Jason@zx2c4.com> 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" We call try_to_generate_entropy() from wait_for_random_bytes(). wait_for_random_bytes() always uses wait_event_interruptible_timeout() when waiting, since it's called by userspace code in restartable contexts, where signals can pend. When entering a busy loop in try_to_generate_entropy(), we should therefore also check to see if any signals are pending, so that a process doesn't get stuck in that loop longer than expected. As well, there's no point in waiting for a full second before trying to generate entropy; instead do it in the opposite order, where we try to generate, and then go into the waitable. Cc: Dominik Brodowski Cc: Theodore Ts'o Signed-off-by: Jason A. Donenfeld --- drivers/char/random.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/drivers/char/random.c b/drivers/char/random.c index edb5b06544da..4c5f515b6080 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -128,11 +128,12 @@ int wait_for_random_bytes(void) =20 do { int ret; + + try_to_generate_entropy(); ret =3D wait_event_interruptible_timeout(crng_init_wait, crng_ready(), H= Z); if (ret) return ret > 0 ? 0 : ret; =20 - try_to_generate_entropy(); } while (!crng_ready()); =20 return 0; @@ -1374,7 +1375,7 @@ static void try_to_generate_entropy(void) return; =20 timer_setup_on_stack(&stack.timer, entropy_timer, 0); - while (!crng_ready()) { + while (!crng_ready() && !signal_pending(current)) { if (!timer_pending(&stack.timer)) mod_timer(&stack.timer, jiffies + 1); mix_pool_bytes(&stack.cycles, sizeof(stack.cycles)); --=20 2.35.1