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dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:35864 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kfcxH-0006GU-Mk for qemu-devel@archiver.kernel.org; Thu, 19 Nov 2020 00:58:03 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:41172) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kfcwV-0005ot-Fq for qemu-devel@nongnu.org; Thu, 19 Nov 2020 00:57:15 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:26246) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1kfcwS-0001LD-Kh for qemu-devel@nongnu.org; Thu, 19 Nov 2020 00:57:14 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1605765431; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=n4vJeXNNVB/w1P1gCqDgXQN9weJjhAoE6dmtNAwoUnY=; b=Ss2APYwgaI1cZ8LmnNf+F4vymqkZZau/5CnhTYTsHDdYcpBK/sE7hLD1av8MMVCj3hum7S wNE0TAdXwwo3e1fLwhuZNYcyvan7LZkAAaCC4ooBLmBAvcdV2pY8t/L2jQwbUbMx/ZhIzP yQ3knTVLq+P7mvjuGwZXyAnlKyLHpnk= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-574-h1zGPZojOW6QMbGHN-ebNg-1; Thu, 19 Nov 2020 00:57:06 -0500 X-MC-Unique: h1zGPZojOW6QMbGHN-ebNg-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 8F4CE800D55; Thu, 19 Nov 2020 05:57:05 +0000 (UTC) Received: from [10.72.13.63] (ovpn-13-63.pek2.redhat.com [10.72.13.63]) by smtp.corp.redhat.com (Postfix) with ESMTP id 47EF95D9D5; Thu, 19 Nov 2020 05:57:01 +0000 (UTC) Subject: Re: [PATCH v2] net/e1000e_core: adjust count if RDH exceeds RDT in e1000e_ring_advance() To: Mauro Matteo Cascella References: <20201113103113.223239-1-mcascell@redhat.com> From: Jason Wang Message-ID: Date: Thu, 19 Nov 2020 13:57:00 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=jasowang@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US Received-SPF: pass client-ip=63.128.21.124; envelope-from=jasowang@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/11/18 23:36:20 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: gaoning.pgn@antgroup.com, 330cjfdn@gmail.com, Dmitry Fleytman , Laszlo Ersek , QEMU Developers Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 2020/11/18 下午4:53, Mauro Matteo Cascella wrote: > On Wed, Nov 18, 2020 at 4:56 AM Jason Wang wrote: >> >> On 2020/11/13 下午6:31, Mauro Matteo Cascella wrote: >>> The e1000e_write_packet_to_guest() function iterates over a set of >>> receive descriptors by advancing rx descriptor head register (RDH) from >>> its initial value to rx descriptor tail register (RDT). The check in >>> e1000e_ring_empty() is responsible for detecting whether RDH has reached >>> RDT, terminating the loop if that's the case. Additional checks have >>> been added in the past to deal with bogus values submitted by the guest >>> to prevent possible infinite loop. This is done by "wrapping around" RDH >>> at some point and detecting whether it assumes the original value during >>> the loop. >>> >>> However, when e1000e is configured to use the packet split feature, RDH is >>> incremented by two instead of one, as the packet split descriptors are >>> 32 bytes while regular descriptors are 16 bytes. A malicious or buggy >>> guest may set RDT to an odd value and transmit only null RX descriptors. >>> This corner case would prevent RDH from ever matching RDT, leading to an >>> infinite loop. This patch adds a check in e1000e_ring_advance() to make sure >>> RDH does not exceed RDT in a single incremental step, adjusting the count >>> value accordingly. >> >> Can this patch solve this issue in another way? >> >> https://patchew.org/QEMU/20201111130636.2208620-1-ppandit@redhat.com/ >> >> Thanks >> > Yes, it does work nicely. Still, I think this patch is useful to avoid > possible inconsistent state in e1000e_ring_advance() when count > 1. So if RDT is odd, it looks to me the following codes in e1000e_write_packet_to_guest() needs to be fixed as well.         base = e1000e_ring_head_descr(core, rxi);         pci_dma_read(d, base, &desc, core->rx_desc_len); Otherwise e1000e may try to read out of descriptor ring. Thanks > > Thank you,