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 81D39C433F5 for ; Fri, 27 May 2022 11:49:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1351874AbiE0Ltm (ORCPT ); Fri, 27 May 2022 07:49:42 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56840 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1352342AbiE0Lpw (ORCPT ); Fri, 27 May 2022 07:45:52 -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 CF95314677D; Fri, 27 May 2022 04:42:27 -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 F178F61D19; Fri, 27 May 2022 11:42:26 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 09AACC385A9; Fri, 27 May 2022 11:42:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1653651746; bh=YAaAnfdN5DGX6izEPZPLbxRmKyDvGykDk8xyS2lO+OE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=bANu/a6KxG0XE7w7jHxMKV/PKmnFg5azMUd7VatrJIyJtz4EgGC0/a2uiEWZ4sKJd PydBRoUZ8/JVdF+PfO/BujyANPKgH6fruCysQgThizwURKzC9wb0guzr3kkaGr+6JQ DWJcgHc/xwBcp75MhKV+HzrVrtTJAROqbIrooTQU= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Thomas Gleixner , Arnd Bergmann , "Russell King (Oracle)" , "Jason A. Donenfeld" Subject: [PATCH 5.17 078/111] arm: use fallback for random_get_entropy() instead of zero Date: Fri, 27 May 2022 10:49:50 +0200 Message-Id: <20220527084830.509591474@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 ff8a8f59c99f6a7c656387addc4d9f2247d75077 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 Reviewed-by: Russell King (Oracle) Signed-off-by: Jason A. Donenfeld Signed-off-by: Greg Kroah-Hartman --- arch/arm/include/asm/timex.h | 1 + 1 file changed, 1 insertion(+) --- a/arch/arm/include/asm/timex.h +++ b/arch/arm/include/asm/timex.h @@ -11,5 +11,6 @@ typedef unsigned long cycles_t; #define get_cycles() ({ cycles_t c; read_current_timer(&c) ? 0 : c; }) +#define random_get_entropy() (((unsigned long)get_cycles()) ?: random_get_entropy_fallback()) #endif