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 DCF50C433FE for ; Fri, 27 May 2022 11:47:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1351876AbiE0LrY (ORCPT ); Fri, 27 May 2022 07:47:24 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56480 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1352144AbiE0Lp3 (ORCPT ); Fri, 27 May 2022 07:45:29 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 526F7133250; Fri, 27 May 2022 04:42:06 -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 3607761D50; Fri, 27 May 2022 11:42:06 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 42BE8C385A9; Fri, 27 May 2022 11:42:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1653651725; bh=N+njQa8dbPvGRCd+m8kR8WWw+lhJD4cHuiN1wI+6arY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=K5v7JD5gnBPv3o35wXmmgZwQ9d4Of+Rmc5P4ls++lF8a613oDLwJkdCQKp4e1eiQg uaZAY3ZvFyTIi4r6gpv25GrIpcqZ1LVnLtGUX8Ay6b7pu/nFTviwkTM3j8G2YOGaJr Qaq96VUMnX7Tsp8ktV1e47odRBZX6kvtgtlgSHh4= 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 5.17 076/111] riscv: use fallback for random_get_entropy() instead of zero Date: Fri, 27 May 2022 10:49:48 +0200 Message-Id: <20220527084830.218540795@linuxfoundation.org> X-Mailer: git-send-email 2.36.1 In-Reply-To: <20220527084819.133490171@linuxfoundation.org> References: <20220527084819.133490171@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()