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=-3.9 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no 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 0D221C4363C for ; Thu, 8 Oct 2020 15:54:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 96BCE215A4 for ; Thu, 8 Oct 2020 15:54:36 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=ziepe.ca header.i=@ziepe.ca header.b="e4G8JbIB" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731376AbgJHPyf (ORCPT ); Thu, 8 Oct 2020 11:54:35 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41726 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731349AbgJHPy2 (ORCPT ); Thu, 8 Oct 2020 11:54:28 -0400 Received: from mail-io1-xd2f.google.com (mail-io1-xd2f.google.com [IPv6:2607:f8b0:4864:20::d2f]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 95101C0613D3 for ; Thu, 8 Oct 2020 08:54:28 -0700 (PDT) Received: by mail-io1-xd2f.google.com with SMTP id y20so2524764iod.5 for ; Thu, 08 Oct 2020 08:54:28 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ziepe.ca; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:content-transfer-encoding:in-reply-to; bh=K87Z76MUaMwGT4jUWUnqmzUL4QRao9GTWVhIdgVOY/E=; b=e4G8JbIBYYn4byga8lFuWrt9CFFn9lYWoAD1LGBR+e/tZ9poYwiZqM7gs3ybG/gIBq zz7dL371KLKSGU4f/NBlLH3fIBgSyxzXtghqEaeYZfJRMNpkI0lMQUcDgm83at78bStx Zc5xkxTsJtNTTgSVb6C5zeNi4HJEQKN4gDzA77kH6lJvcIcwRV2pmVwq5/PgqmSrASUG xbrn92HnLUWQ6gUEymthXOXuR+hO60OOsqKfgFo7bBNGjVva2ymBMjttK1FZrqr6B/G7 ZlF+88bveRMRKdWikJfadYEq0z02G/ow6P9+CaJF4ELyIevNQlcDIqcngP7Yq/AUPwvN W9Ew== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:content-transfer-encoding :in-reply-to; bh=K87Z76MUaMwGT4jUWUnqmzUL4QRao9GTWVhIdgVOY/E=; b=XarWjSX8F+IqBDKO2jl76ij4037qtfl4MQIBUmSWVDmQnfGZXhP1U2hz3bU+gf8omI 9aENvqYyQg6NajYVVP51r5JxBMDUkL6bnh6mOXNAT5TnxpolRkp40ZxXnJUaXxnca+lF /lQdK0FZowBRQ9WoEp/nimL0kiEBpRxucQ8kyKtYNpgw43m7LWb3fOQBePYF/t+9cK8z 8NkabE1fYJtV4xQ3ernZYjUOvsymcBbH/VL1ykrJ64nmjkuWLGB+lFeOQ1lIUOWM9O1+ uac7j3RVx93HYw4WaRXMnyPqL93i7xtHkTsfLqmwMLD8bQOes8IYCk4glcFHWuHmg08T yvsQ== X-Gm-Message-State: AOAM533FlEiLXZNVOT6eNTdg0jksIMDXYbze/ta1qmNo7nKGuQOWU1n5 OFIKjJEPqSkSEahXA4KvdQgTYQ== X-Google-Smtp-Source: ABdhPJxhx7JoupFXMCiMHmWdoKyUTtxiD0NERl7t1I0IK9IlW8bYTtunZy46ck3A+NMEuATEqSoQrw== X-Received: by 2002:a02:6a4f:: with SMTP id m15mr7245672jaf.2.1602172467984; Thu, 08 Oct 2020 08:54:27 -0700 (PDT) Received: from ziepe.ca ([206.223.160.26]) by smtp.gmail.com with ESMTPSA id g17sm2801603ilq.15.2020.10.08.08.54.27 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 08 Oct 2020 08:54:27 -0700 (PDT) Received: from jgg by mlx with local (Exim 4.94) (envelope-from ) id 1kQYFO-001WnB-6r; Thu, 08 Oct 2020 12:54:26 -0300 Date: Thu, 8 Oct 2020 12:54:26 -0300 From: Jason Gunthorpe To: Jan Engelhardt Cc: Nathan Chancellor , "Gustavo A. R. Silva" , Linus Torvalds , Kees Cook , Greg KH , Linux Kernel Mailing List , linux-rdma@vger.kernel.org, clang-built-linux@googlegroups.com Subject: Re: remaining flexible-array conversions Message-ID: <20201008155426.GE5177@ziepe.ca> References: <6342c465-e34b-3e18-cc31-1d989926aebd@embeddedor.com> <20200424034704.GA12320@ubuntu-s3-xlarge-x86> <20200424121553.GE26002@ziepe.ca> <36r41qn8-87o3-2pr1-856p-040167pq097@vanv.qr> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <36r41qn8-87o3-2pr1-856p-040167pq097@vanv.qr> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Oct 08, 2020 at 05:24:03PM +0200, Jan Engelhardt wrote: > In the case of the RDMA headers, even if we assume best conditions -- > a block of malloc(sizeof(struct ib_uverbs_create_cq_resp) + > sizeof(u64)*N) and not some struct -- it smells a lot like undefined > behavior, because ib_uverbs_create_cq_resp::driver_data accesses data > as u64 driver_data[] is never accessed, it is only used as a pointer. Aliasing should be OK because all accesses to those bytes consistently use u32. Fixing the compiler warning requires significant edits of kernel and user code, not entirely sure it is worthwhile. If someone wants to do it let me know and I'll give some guidance. Jason