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 38AAEC433FE for ; Fri, 15 Apr 2022 06:41:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1350568AbiDOGoN (ORCPT ); Fri, 15 Apr 2022 02:44:13 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57676 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1350562AbiDOGoM (ORCPT ); Fri, 15 Apr 2022 02:44:12 -0400 Received: from mail-ed1-x529.google.com (mail-ed1-x529.google.com [IPv6:2a00:1450:4864:20::529]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 270F9AFAE4; Thu, 14 Apr 2022 23:41:44 -0700 (PDT) Received: by mail-ed1-x529.google.com with SMTP id 11so3927524edw.0; Thu, 14 Apr 2022 23:41:44 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=5H0NkTvkK9p/s/zFBLeQhRPlAabxLu86mDFZRjaQsXc=; b=iyFOa4B+WwNsN+h+lDNBD7iDxm1raLPy02+uAnAc+XNZRX1w70gpAZqtygmAFeXjSg 1GUSmiurrP71xGOpLq2V4+8hSIuCzS5F96z6jeOIkzrISvWEEudwsgm6RzwwlnXcPG9a qF7a2xTHOx8a5GiJsY9lEWF+Uho6ZA7vaNxdHeBlI/Wi9LjDuddeBUTS0lm0eGkImDje Y7lTz1NSrxwSn3xQtTvCQRVjxClQi+Dz2ezWPmHqsU5nI68lMFWm74KyKRimhArp1eDN 1y8GQ2Z09zw3xJSYv4or3YzrTl19q7VEvrFUNdkgSWq3/gFIAakmfJp2mOKtJhlto7m3 0BhA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=5H0NkTvkK9p/s/zFBLeQhRPlAabxLu86mDFZRjaQsXc=; b=Xm4y6PmYs+lspXFpVj8vE/WicT+iORkJhz34bEFRFNKJzgRf5HwmDN/8qqT9Sg4W6K GFgTy9bQQQnB7HzvC22OHQtk5PqsSeras7//nCs4DqU4UN2rjfsiMFP2pMjk6tswO3sG esBog/yYnpXDrLLj4beSAAGjkiCCTDbkFGYrVKHSDA1bQTZFcwfAtBjHWcGM/gvbG+TY Efa/Sj1FUru6MauK6uIi32QLN/f1HJCIUvfo1EBdZ5MSDLIafZMeNBpaDYA5CNzC7m4A I2lQvmbRPpoxCygRlrFpS/TBV928uL1Fi4fmQNybRpyBj8ia0u0V5mmRKptEKcEj4Wdl Mkkg== X-Gm-Message-State: AOAM532tVHZPtPBd5HHRO78VFPdJyOuMum4Me8jvg+U4M+vEKk/1HX1f iYSnbWxI5ZkWmDfyK9hcoOOSv7truu+0EKB/ X-Google-Smtp-Source: ABdhPJxavdBJugZjTO5NWzDHmyFQ192W3DPA51QTlL3JUiZqLUMj0ftkoqVV6vkYR+MyGK8HDeanwQ== X-Received: by 2002:a05:6402:1385:b0:413:2bc6:4400 with SMTP id b5-20020a056402138500b004132bc64400mr6918217edv.94.1650004902841; Thu, 14 Apr 2022 23:41:42 -0700 (PDT) Received: from anparri (host-79-52-64-69.retail.telecomitalia.it. [79.52.64.69]) by smtp.gmail.com with ESMTPSA id j23-20020a1709064b5700b006e87ae0c111sm1362808ejv.123.2022.04.14.23.41.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 14 Apr 2022 23:41:41 -0700 (PDT) Date: Fri, 15 Apr 2022 08:41:33 +0200 From: Andrea Parri To: "Michael Kelley (LINUX)" Cc: KY Srinivasan , Haiyang Zhang , Stephen Hemminger , Wei Liu , Dexuan Cui , Stefano Garzarella , David Miller , Jakub Kicinski , Paolo Abeni , "linux-hyperv@vger.kernel.org" , "virtualization@lists.linux-foundation.org" , "netdev@vger.kernel.org" , "linux-kernel@vger.kernel.org" Subject: Re: [RFC PATCH 1/6] hv_sock: Check hv_pkt_iter_first_raw()'s return value Message-ID: <20220415064133.GA2961@anparri> References: <20220413204742.5539-1-parri.andrea@gmail.com> <20220413204742.5539-2-parri.andrea@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Fri, Apr 15, 2022 at 03:33:23AM +0000, Michael Kelley (LINUX) wrote: > From: Andrea Parri (Microsoft) Sent: Wednesday, April 13, 2022 1:48 PM > > > > The function returns NULL if the ring buffer has no enough space > > available for a packet descriptor. The ring buffer's write_index > > The first sentence wording is a bit scrambled. I think you mean the > ring buffer doesn't contain enough readable bytes to constitute a > packet descriptor. Indeed, replaced with your working. > > is in memory which is shared with the Hyper-V host, its value is > > thus subject to being changed at any time. > > This second sentence is true, but I'm not making the connection > with the code change below. Evidently, there is some previous > check made to ensure that enough bytes are available to be > received when hvs_stream_dequeue() is called, so we assumed that > NULL could never be returned? I looked but didn't find such a check, > so maybe I didn't look carefully enough. But now we are assuming > that Hyper-V might have invalidated that previous check by > subsequently changing the write_index in a bogus way? So now, NULL > could be returned when previously we assumed it couldn't. I think you're looking for hvs_stream_has_data(). (Previous checks apart, hvs_stream_dequeue() will "dereference" the pointer so...) Thanks, Andrea