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=-7.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,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 E452BC64E7C for ; Wed, 2 Dec 2020 14:15:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8A13721D7F for ; Wed, 2 Dec 2020 14:15:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728042AbgLBOPY (ORCPT ); Wed, 2 Dec 2020 09:15:24 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40444 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726071AbgLBOPY (ORCPT ); Wed, 2 Dec 2020 09:15:24 -0500 Received: from mail-wr1-x443.google.com (mail-wr1-x443.google.com [IPv6:2a00:1450:4864:20::443]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BC575C0613D4; Wed, 2 Dec 2020 06:14:43 -0800 (PST) Received: by mail-wr1-x443.google.com with SMTP id o1so4140974wrx.7; Wed, 02 Dec 2020 06:14:43 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=Y09Yc6Gy3QraLOEdgVpi1+sbCU87xyp9KMOciYZdYPA=; b=LNF0QjiPxwKDMiRR+dopQBjFpbGq4dzE9u/irqWJu5T5XzfQbwmo9n9PGB7Mo7HtCo 3It45M6Rm1BkVuNDDaukQ85737dlDJfVSMQT9Ofmw2rSWYZI+59dp17Zsv4Ao9UdFkCT j9nMQ/LJ06ItQ0+0q0DS3siV822j3qLalfmQGki93R/JJUrIr8ayLEqOkUhRioPpjZi6 qdJnjtF7tAiWk3iNkEgxFYgS1BT2KVo5WUFVGFqfKdbrnovwGikOo57zfFq+1ZGBv6ZK EPWO6Ql9DrcBlc4n+NhNvfKvRtR81MnHJBr7rhk5cM+agph5kRdl5Ixj332dzHz5K5aV hwvw== 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:in-reply-to; bh=Y09Yc6Gy3QraLOEdgVpi1+sbCU87xyp9KMOciYZdYPA=; b=EQCd0FlKvs6B1T+y8XBvZbCzhTns8bevogl3WTDx/o9EgoLRW0DdMByhKCoZTla13u Bw5T4LRaKM4OFOBR24Vl1N00OP+f4kS/2G1bsnQEJQDaARdf6+88840gQnKNXwjJ0Mvx EZ/9IXyY/a8/D5QTl0WkEbpvFU6gbSPkIOWYwd9UIqtiiUPGPQ+droH1UxocK3GhqTc8 oIKVz8EJh3A2GLYrgdHFaKWqmyj/QPoZrac+mAJSrnhCXYmTLnYKXOag7ncprNwr2B0Y v4Sy4JN5ewD79uXteQFhTuQRJQR7FAJ4pNle7usxCw08JDekd+ShlqpHFz8AMBN6hXvY MtAA== X-Gm-Message-State: AOAM532UHl+htfOlk5zKpFmo/V/AKRzL+oLMXvKDntpSo9ujFlv+TArO OB+6tB1YhyTyKYu7mRUanIY= X-Google-Smtp-Source: ABdhPJzvfSW63NIYgCI5jR4y00vXV9+cKa8GVNmTDBb9hfiIlPMuaihyZaPr6TcAC+oiCi4K4g7T6Q== X-Received: by 2002:a05:6000:82:: with SMTP id m2mr3707931wrx.314.1606918482270; Wed, 02 Dec 2020 06:14:42 -0800 (PST) Received: from andrea (host-95-239-64-30.retail.telecomitalia.it. [95.239.64.30]) by smtp.gmail.com with ESMTPSA id o2sm2247428wrq.37.2020.12.02.06.14.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 02 Dec 2020 06:14:41 -0800 (PST) Date: Wed, 2 Dec 2020 15:14:33 +0100 From: Andrea Parri To: Wei Liu Cc: linux-kernel@vger.kernel.org, linux-hyperv@vger.kernel.org, "K . Y . Srinivasan" , Haiyang Zhang , Stephen Hemminger , Michael Kelley , Juan Vazquez , Saruhan Karademir Subject: Re: [PATCH v2 2/7] Drivers: hv: vmbus: Avoid double fetch of msgtype in vmbus_on_msg_dpc() Message-ID: <20201202141433.GA24359@andrea> References: <20201202092214.13520-1-parri.andrea@gmail.com> <20201202092214.13520-3-parri.andrea@gmail.com> <20201202122254.zjhu3cfcq3zwvmvu@liuwe-devbox-debian-v2> <20201202133716.GA22763@andrea> <20201202134004.5tgrbyijrhvwwmk2@liuwe-devbox-debian-v2> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201202134004.5tgrbyijrhvwwmk2@liuwe-devbox-debian-v2> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Dec 02, 2020 at 01:40:04PM +0000, Wei Liu wrote: > On Wed, Dec 02, 2020 at 02:37:16PM +0100, Andrea Parri wrote: > > > > @@ -1072,12 +1073,19 @@ void vmbus_on_msg_dpc(unsigned long data) > > > > /* no msg */ > > > > return; > > > > > > > > + /* > > > > + * The hv_message object is in memory shared with the host. The host > > > > + * could erroneously or maliciously modify such object. Make sure to > > > > + * validate its fields and avoid double fetches whenever feasible. > > > > + */ > > > > + > > > > hdr = (struct vmbus_channel_message_header *)msg->u.payload; > > > > + msgtype = hdr->msgtype; > > > > > > Should READ_ONCE be used here? > > > > I think it should. Thank you for pointing this out. > > Glad I can help. > > The same comment applies to other patches as well, of course. (As discussed offline/for reference:) I can spot a similar case in patch #3; however, #4 is supposed to make that access 'non-shared'. I should probably just squash patches #3 and #4; I'll try to do so in v3... Thanks, Andrea