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=-0.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, 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 0DE70C3279B for ; Fri, 6 Jul 2018 15:39:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B6AB823EF9 for ; Fri, 6 Jul 2018 15:39:18 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="eNQTSSqM" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B6AB823EF9 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.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 S933390AbeGFPjP (ORCPT ); Fri, 6 Jul 2018 11:39:15 -0400 Received: from mail-pf0-f194.google.com ([209.85.192.194]:36668 "EHLO mail-pf0-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932703AbeGFPjN (ORCPT ); Fri, 6 Jul 2018 11:39:13 -0400 Received: by mail-pf0-f194.google.com with SMTP id u16-v6so8745415pfh.3; Fri, 06 Jul 2018 08:39:13 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=+W5JAPOxPLWd5wrzgU4J396wSwDwZxxIrS3Cta+IMmA=; b=eNQTSSqM7PfbXWvGuW/agmyme8Mb2XMqYc49WbfkdeHEF+wwDceLMD8SSX58gE3rdL 3/jcuIvrVDobzgohKdTlyLRvKa+5ORi3/so/AV4gdASGZZnZy3pViQgXgy5YC3Ua2kfq 6IuRZgPsABsnoCuOZt9XjYj++Jf3K2Fa3hvaA15fFn9rD3eM0H2LrVuHLLz1MPdpUGsd OCAfMHCkwFvfrrb35+xSvyTZtAuunvHtinDiH9JFHMZrj3KyZvBHRDgZpUCJcJ7KC3I+ 9UgNbKC/JbKnBU0ad2cvYXF+2pkmdfJRF+lg/VGUFjnVRtS92Ti11C82sQYOT9eJOUm4 G4ow== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=+W5JAPOxPLWd5wrzgU4J396wSwDwZxxIrS3Cta+IMmA=; b=tbNg6TSOhrhf7K0dX13Uo69BVNayrx1Rv7PAA5Vcmq+A3NzU03uEzDNXaybverm8RP MbNVmkxXFA/GlDirON3MZFqTpesmv74e16A78m+Za4wXg09blbu69vRV4hw8kpzN0D31 DttyQHSnYh3CGiHAz/jmCk6BpNmtrSeF7GRREiYH3fdNfKaNED6QmVntJCWtbus11LTE k0df117pXvrcinm8fcQdfWYagmyITBdvNy+x43vOYOM8NaWoITh4dApYZf4ZJ2AKCY/w SmNEjD3FxJcI7vrDYRWxZHe7FONLdcUUqK46Ukd5MvVg8V1d7Hhn6fF9H0dC5Wr31A+s ZkLw== X-Gm-Message-State: APt69E0WaXNJqhOxTkuiZU5QmfzuEHK/cVuqnWlxaAPCBd4ixwLV8/s0 1HHHSj/9nrtBWvvOAERUu9PmIK/s X-Google-Smtp-Source: AAOMgpc0FrU9pjV8eUtJWHD0J5CL9WXR8P5gdZrb7y/dqqggCv5rip+qfL3pIjCUb0qm+EsCs14v/g== X-Received: by 2002:a63:8c5:: with SMTP id 188-v6mr9686838pgi.97.1530891552822; Fri, 06 Jul 2018 08:39:12 -0700 (PDT) Received: from ?IPv6:2620:15c:2c1:200:55c7:81e6:c7d8:94b? ([2620:15c:2c1:200:55c7:81e6:c7d8:94b]) by smtp.gmail.com with ESMTPSA id u42-v6sm15889481pgn.1.2018.07.06.08.39.11 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 06 Jul 2018 08:39:11 -0700 (PDT) Subject: Re: [PATCH] ipv4: fib: avoid NULL dereference To: Mark Rutland , Eric Dumazet Cc: linux-kernel@vger.kernel.org, Alexey Kuznetsov , "David S . Miller" , Hideaki YOSHIFUJI , netdev@vger.kernel.org References: <20180706142836.1822-1-mark.rutland@arm.com> <3ad39534-400a-8d4e-ac50-94eb5655e565@gmail.com> <20180706145728.57utqqrjzq7iupnh@lakrids.cambridge.arm.com> From: Eric Dumazet Message-ID: Date: Fri, 6 Jul 2018 08:39:11 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 MIME-Version: 1.0 In-Reply-To: <20180706145728.57utqqrjzq7iupnh@lakrids.cambridge.arm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/06/2018 07:57 AM, Mark Rutland wrote: > On Fri, Jul 06, 2018 at 07:47:04AM -0700, Eric Dumazet wrote: >> >> >> On 07/06/2018 07:28 AM, Mark Rutland wrote: >>> In tnode_free() we iterate over a callback_head list with a while loop. >>> At the start of the loop body we generate the next head pointer, and at >>> the end of the loop body we generate the tn pointer for the next >>> iteration of the loop by using container_of() on the head pointer to >>> find the tnode, and deriving the kv pointer from this. >>> >>> In the final iteration of the loop, this means that we derive a pointer >>> from NULL, which is undefined behaviour, which UBSAN detects: >> >> There is no dereference, your patch title is misleading. >> >> UBSAN might be fooled, not the C compiler. > > I'm happy to change the title to "avoid undefined behaviour". > Are you planning to change this as well ? include/linux/stddef.h:19:#define offsetof(TYPE, MEMBER) ((size_t)&((TYPE *)0)->MEMBER) (And probably dozens of other locations)