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 81FE5C433EF for ; Fri, 13 May 2022 06:26:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1377378AbiEMG0w (ORCPT ); Fri, 13 May 2022 02:26:52 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35468 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1377308AbiEMG0Z (ORCPT ); Fri, 13 May 2022 02:26:25 -0400 Received: from isilmar-4.linta.de (isilmar-4.linta.de [136.243.71.142]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E6B8827CC0 for ; Thu, 12 May 2022 23:26:22 -0700 (PDT) X-isilmar-external: YES X-isilmar-external: YES Received: from owl.dominikbrodowski.net (owl.brodo.linta [10.2.0.111]) by isilmar-4.linta.de (Postfix) with ESMTPSA id F07F2201406; Fri, 13 May 2022 06:26:05 +0000 (UTC) Received: by owl.dominikbrodowski.net (Postfix, from userid 1000) id D3E92809A3; Fri, 13 May 2022 08:23:40 +0200 (CEST) Date: Fri, 13 May 2022 08:23:40 +0200 From: Dominik Brodowski To: "Jason A. Donenfeld" Cc: linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/2] random: avoid init'ing twice in credit race Message-ID: References: <20220509121409.529788-1-Jason@zx2c4.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220509121409.529788-1-Jason@zx2c4.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Am Mon, May 09, 2022 at 02:14:08PM +0200 schrieb Jason A. Donenfeld: > Since all changes of crng_init now go through credit_init_bits(), we can > fix a long standing race in which two concurrent callers of > credit_init_bits() have the new bit count >= some threshold, but are > doing so with crng_init as a lower threshold, checked outside of a lock, > resulting in crng_reseed() or similar being called twice. Sidenote: crng_reseed() did manage quite fine if called twice in short order. > In order to fix this, we can use the original cmpxchg value of the bit > count, and only change crng_init when the bit count transitions from > below a threshold to meeting the threshold. > > Cc: Dominik Brodowski > Signed-off-by: Jason A. Donenfeld Reviewed-by: Dominik Brodowski Thanks, Dominik