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 7040EC433EF for ; Fri, 1 Apr 2022 16:37:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1348578AbiDAQjf (ORCPT ); Fri, 1 Apr 2022 12:39:35 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47254 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S243238AbiDAQgU (ORCPT ); Fri, 1 Apr 2022 12:36:20 -0400 Received: from mail-ed1-x531.google.com (mail-ed1-x531.google.com [IPv6:2a00:1450:4864:20::531]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 932D360ABA; Fri, 1 Apr 2022 09:09:27 -0700 (PDT) Received: by mail-ed1-x531.google.com with SMTP id y10so3499766edv.7; Fri, 01 Apr 2022 09:09:27 -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=OsRh1+OUJjafmw1DLalzmHZY/d86wBXtRZCzuhQ9mCU=; b=CyaAXZ+IZKz9gQ7HVvoq92nHK87TtxUVRVI+dFs2B2UzLDczPui7Zt+1vUbmgx3Bdt dpkGF1v81vHMc3grDBckD5+il7kl40JL+LMt+glIHncxGx42UclHTuL+3qQhARf5up8N VYAPCe5GDasxGVJG81cP9vsjjlvjLoYOWgiyObxxMnwnGxPWXeBNFSNTaKqi/FmvrO+n cpm0PirjT1Ego1eSZj2BOi3r0ESuibWg+TNdxIiE16r+fJeqD58K2Y2fokGGZxHciWzk WijuccdcZfn+O8TFWAdhtCW11jP4jquKrxZZMHZQdWrBmCI7sakO9I41pBw8+JcKMa56 l9FA== 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=OsRh1+OUJjafmw1DLalzmHZY/d86wBXtRZCzuhQ9mCU=; b=SE8/ecDw2ERYSDtcNTnVxa0uG9QGL1hak47UYukw5vwvflOfHhxXcsDh0RtI68d38b TbHTiKXaue5thcli90lTnzgMsgQViml+nEbFDen4hUYutOc8FXTr/iZresHV69uSyMik KN7g2HsMiYHTlWufuT2ajBVYB/h+eiL3w/EwB+MR+YYSdnGEe8i7jU5k9rz5d8k9sfUe xXzae0k8YMuwczpN9y3k71AuCjJDloX8zVRuMDylkbJQhZsD0k6cUZiXrCVidDFQ7iWD mUK15ru7+MDm3R7Onazg68wK/1IeKa1xHHFoCfZAuik8UkGktjhbUwWv0AWbQaT2E3m9 chbw== X-Gm-Message-State: AOAM533pCuzN8T0vGuvkeBUGSFL4c4co6Dd4db/sYu8lNuesMuFwV9WA g0oeSx1bkgewij65s53aww0= X-Google-Smtp-Source: ABdhPJzv5bt7f0IiLlBql9Y5PWwGhZWdPagcJ+jWbTiZA17jQAlP+7vQNkZuTUH5vvkRzeIERD4AwA== X-Received: by 2002:a05:6402:4250:b0:419:5e89:a40f with SMTP id g16-20020a056402425000b004195e89a40fmr21974008edb.319.1648829365926; Fri, 01 Apr 2022 09:09:25 -0700 (PDT) Received: from anparri (host-82-59-4-232.retail.telecomitalia.it. [82.59.4.232]) by smtp.gmail.com with ESMTPSA id a21-20020a170906275500b006d10c07fabesm1158632ejd.201.2022.04.01.09.09.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 01 Apr 2022 09:09:25 -0700 (PDT) Date: Fri, 1 Apr 2022 18:09:22 +0200 From: Andrea Parri To: "Michael Kelley (LINUX)" Cc: KY Srinivasan , Haiyang Zhang , Stephen Hemminger , Wei Liu , Dexuan Cui , Wei Hu , Lorenzo Pieralisi , Rob Herring , Krzysztof Wilczynski , Bjorn Helgaas , "linux-hyperv@vger.kernel.org" , "linux-pci@vger.kernel.org" , "linux-kernel@vger.kernel.org" Subject: Re: [RFC PATCH 3/4] Drivers: hv: vmbus: Introduce vmbus_sendpacket_getid() Message-ID: <20220401160922.GB437893@anparri> References: <20220328144244.100228-1-parri.andrea@gmail.com> <20220328144244.100228-4-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: linux-kernel@vger.kernel.org > > @@ -354,6 +354,8 @@ int hv_ringbuffer_write(struct vmbus_channel *channel, > > } > > desc = hv_get_ring_buffer(outring_info) + old_write; > > desc->trans_id = (rqst_id == VMBUS_NO_RQSTOR) ? requestid : rqst_id; > > + if (trans_id) > > + *trans_id = desc->trans_id; > > This line should *not* read the trans_id out of the ring buffer, since that > memory is shared with the Hyper-V host and subject to being maliciously > changed by the host. Need to set *trans_id only from local variables, and > somehow ensure the compiler doesn't generate code that reads the value > from the ring buffer. Maybe mark the desc->trans_id field as volatile, or cast > it as such? Or does WRITE_ONCE() work when setting it? I'd stick to WRITE_ONCE() (with a comment). Good catch! Thanks, Andrea