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 4921AC433F5 for ; Fri, 27 May 2022 08:53:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240348AbiE0Ixt (ORCPT ); Fri, 27 May 2022 04:53:49 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57490 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1350153AbiE0Iwz (ORCPT ); Fri, 27 May 2022 04:52:55 -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 0A47B5C36C; Fri, 27 May 2022 01:52:31 -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 84257B823DE; Fri, 27 May 2022 08:52:30 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9E819C385A9; Fri, 27 May 2022 08:52:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1653641549; bh=N+njQa8dbPvGRCd+m8kR8WWw+lhJD4cHuiN1wI+6arY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=thp6IyqQ6sPg8NGAhhu3HIHyrIKuPqKxh2oDD201S9wrIv8KKN/Bng7OysZNeLvuQ cuMBXHN7er/WcPXOAjaPuDK6XfBDGu3CnjPQKpt5Z6dnV91qIwJ/MJc1yoW45tKNqv Yh6jo06T9kgFfYZQ/CqsMbQBojU0Jq6FY6hHtV+M= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Thomas Gleixner , Arnd Bergmann , Paul Walmsley , Palmer Dabbelt , "Jason A. Donenfeld" Subject: [PATCH 5.18 12/47] riscv: use fallback for random_get_entropy() instead of zero Date: Fri, 27 May 2022 10:49:52 +0200 Message-Id: <20220527084803.239225120@linuxfoundation.org> X-Mailer: git-send-email 2.36.1 In-Reply-To: <20220527084801.223648383@linuxfoundation.org> References: <20220527084801.223648383@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 6d01238623faa9425f820353d2066baf6c9dc872 upstream. In the event that random_get_entropy() can't access a cycle counter or similar, falling back to returning 0 is really not the best we can do. Instead, at least calling random_get_entropy_fallback() would be preferable, because that always needs to return _something_, even falling back to jiffies eventually. It's not as though random_get_entropy_fallback() is super high precision or guaranteed to be entropic, but basically anything that's not zero all the time is better than returning zero all the time. Cc: Thomas Gleixner Cc: Arnd Bergmann Cc: Paul Walmsley Acked-by: Palmer Dabbelt Reviewed-by: Palmer Dabbelt Signed-off-by: Jason A. Donenfeld Signed-off-by: Greg Kroah-Hartman --- arch/riscv/include/asm/timex.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/arch/riscv/include/asm/timex.h +++ b/arch/riscv/include/asm/timex.h @@ -41,7 +41,7 @@ static inline u32 get_cycles_hi(void) static inline unsigned long random_get_entropy(void) { if (unlikely(clint_time_val == NULL)) - return 0; + return random_get_entropy_fallback(); return get_cycles(); } #define random_get_entropy() random_get_entropy()