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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]:38672 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kbx5N-0007d1-HZ for qemu-devel@archiver.kernel.org; Sun, 08 Nov 2020 21:39:13 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:41020) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kbx4T-0007CQ-4x for qemu-devel@nongnu.org; Sun, 08 Nov 2020 21:38:17 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:28710) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1kbx4P-0003YT-Gq for qemu-devel@nongnu.org; Sun, 08 Nov 2020 21:38:16 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1604889492; 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=t3pWU1gxZ+akoCSpZHt44RAwt+4e84oVO00iGuAkT74=; b=J72QUDLu1n+0DvtJCdV/59tvkycwMPXkR8S8vHfYl8tRwqNYhyN0qrjHVN+smOf0p1k6ui cISYMmZV/5cbI7ePstTa2/ADxSZqKpZOVV0RRLGHd/BjMOCqrzmVcsGusoCGj+0c8kxx9x Hf49teLy/PfqdtqsyzYHDzgonvJqwlU= 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-310-m7EigrZaOgus109Z_DtthQ-1; Sun, 08 Nov 2020 21:38:07 -0500 X-MC-Unique: m7EigrZaOgus109Z_DtthQ-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 8B4EA87950D; Mon, 9 Nov 2020 02:38:05 +0000 (UTC) Received: from [10.72.12.244] (ovpn-12-244.pek2.redhat.com [10.72.12.244]) by smtp.corp.redhat.com (Postfix) with ESMTP id 457771002D76; Mon, 9 Nov 2020 02:38:03 +0000 (UTC) Subject: Re: [PATCH] net/e1000e_core: make sure RDH never exceeds RDT in e1000e_ring_advance() To: Mauro Matteo Cascella , qemu-devel@nongnu.org References: <20201105105616.327593-1-mcascell@redhat.com> From: Jason Wang Message-ID: Date: Mon, 9 Nov 2020 10:38:01 +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: <20201105105616.327593-1-mcascell@redhat.com> X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 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 = 2020/11/08 21:14:16 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 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_H5=-1, RCVD_IN_MSPIKE_WL=-0.01, 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@gmail.com, lersek@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 2020/11/5 下午6:56, 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 never exceed RDT. > > This issue was independently reported by Gaoning Pan (Zhejiang University) > and Cheolwoo Myung. > > Signed-off-by: Mauro Matteo Cascella > Reported-by: Gaoning Pan > Reported-by: Cheolwoo Myung <330cjfdn@gmail.com> > --- > References: > https://git.qemu.org/?p=qemu.git;a=commit;h=dd793a74882477ca38d49e191110c17dfe > https://git.qemu.org/?p=qemu.git;a=commit;h=4154c7e03fa55b4cf52509a83d50d6c09d743b7 > http://www.intel.com/content/dam/doc/datasheet/82574l-gbe-controller-datasheet.pdf > > hw/net/e1000e_core.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/hw/net/e1000e_core.c b/hw/net/e1000e_core.c > index bcd186cac5..4c4d14b6ed 100644 > --- a/hw/net/e1000e_core.c > +++ b/hw/net/e1000e_core.c > @@ -831,6 +831,10 @@ e1000e_ring_advance(E1000ECore *core, const E1000E_RingInfo *r, uint32_t count) > { > core->mac[r->dh] += count; > > + if (core->mac[r->dh] > core->mac[r->dt]) { > + core->mac[r->dh] = core->mac[r->dt]; > + } > + > if (core->mac[r->dh] * E1000_RING_DESC_LEN >= core->mac[r->dlen]) { > core->mac[r->dh] = 0; > } A question here. When count > 1, is this correct to reset dh here? Thanks