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 X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 58A2BC6778F for ; Mon, 9 Jul 2018 09:35:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 11C5320857 for ; Mon, 9 Jul 2018 09:35:54 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 11C5320857 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932695AbeGIJfu (ORCPT ); Mon, 9 Jul 2018 05:35:50 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:51544 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S932366AbeGIJfs (ORCPT ); Mon, 9 Jul 2018 05:35:48 -0400 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.rdu2.redhat.com [10.11.54.3]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 24BEC83207; Mon, 9 Jul 2018 09:35:48 +0000 (UTC) Received: from warthog.procyon.org.uk (ovpn-120-149.rdu2.redhat.com [10.10.120.149]) by smtp.corp.redhat.com (Postfix) with ESMTP id 6C719111E3E8; Mon, 9 Jul 2018 09:35:47 +0000 (UTC) Organization: Red Hat UK Ltd. Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903 From: David Howells In-Reply-To: <10670.1531128774@warthog.procyon.org.uk> References: <10670.1531128774@warthog.procyon.org.uk> <20180708210154.10423-4-ebiggers3@gmail.com> <20180708210154.10423-1-ebiggers3@gmail.com> Cc: dhowells@redhat.com, Eric Biggers , Alexander Viro , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Eric Biggers Subject: Re: [PATCH 03/18] fs_context: fix detecting full log buffer MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-ID: <10921.1531128946.1@warthog.procyon.org.uk> Date: Mon, 09 Jul 2018 10:35:46 +0100 Message-ID: <10922.1531128946@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 2.78 on 10.11.54.3 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.1]); Mon, 09 Jul 2018 09:35:48 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.1]); Mon, 09 Jul 2018 09:35:48 +0000 (UTC) for IP:'10.11.54.3' DOMAIN:'int-mx03.intmail.prod.int.rdu2.redhat.com' HELO:'smtp.corp.redhat.com' FROM:'dhowells@redhat.com' RCPT:'' To: unlisted-recipients:; (no To-header on input) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org David Howells wrote: > > When 'head' and 'tail' wrap around, 'log->head - log->tail' will be > > something like '4 - 252 = -248', and comparing that directly to the > > array size is wrong. Fix by casting to 'u8'. > > I think a better fix is to use CIRC_CNT() or CIRC_SPACE(). Or it would be - if CIRC_CNT() and CIRC_SPACE() didn't leave a hole in the buffer - but that's unnecessary if the head and tail counters can hold 2x the ring size or more. David