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=-6.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS autolearn=ham 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 8A376C10F26 for ; Tue, 31 Mar 2020 10:42:51 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 592FF20838 for ; Tue, 31 Mar 2020 10:42:51 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="UgG1udvh" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 592FF20838 Authentication-Results: mail.kernel.org; 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]:35700 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jJEM6-0002zC-HD for qemu-devel@archiver.kernel.org; Tue, 31 Mar 2020 06:42:50 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:51293) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jJELB-00023I-5H for qemu-devel@nongnu.org; Tue, 31 Mar 2020 06:41:54 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1jJEL9-0007Hv-VQ for qemu-devel@nongnu.org; Tue, 31 Mar 2020 06:41:53 -0400 Received: from us-smtp-2.mimecast.com ([205.139.110.61]:48800 helo=us-smtp-delivery-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1jJEL9-0007Hh-QV for qemu-devel@nongnu.org; Tue, 31 Mar 2020 06:41:51 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1585651311; 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=Z9HYddgyBw229ylVeLRdPHtQsfSAeGvqQsGQHL6SkYA=; b=UgG1udvhd8UcWXJ+DbkKsd52K+24DSh/ywcjaIdOMAyf3pTZcxoPYvp1KSTGOpwMK+zKvW gETIw4gGcwug8q0LJmJGjJEFAZDNuAgLlHa3fq1bS1uhK9VX8C6zzVhWbZyB3ZaTaSt05e s0khKzXFq910obEfkLshApulqkY9EIU= 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-306-CpAbOpmcNwqc0Y8t4yaFAA-1; Tue, 31 Mar 2020 06:41:50 -0400 X-MC-Unique: CpAbOpmcNwqc0Y8t4yaFAA-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 5E6161B18BC2; Tue, 31 Mar 2020 10:41:48 +0000 (UTC) Received: from maximlenovopc.usersys.redhat.com (unknown [10.35.206.223]) by smtp.corp.redhat.com (Postfix) with ESMTP id F0B8460BE0; Tue, 31 Mar 2020 10:41:45 +0000 (UTC) Message-ID: Subject: Re: [PATCH v6 07/42] nvme: refactor nvme_addr_read From: Maxim Levitsky To: Klaus Birkelund Jensen Date: Tue, 31 Mar 2020 13:41:44 +0300 In-Reply-To: <20200331053948.ompv75njpyhlti7i@apples.localdomain> References: <20200316142928.153431-1-its@irrelevant.dk> <20200316142928.153431-8-its@irrelevant.dk> <1fb18481dfcfa17c2395f3bcded0aef787badfc7.camel@redhat.com> <20200331053948.ompv75njpyhlti7i@apples.localdomain> Mime-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 205.139.110.61 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: Kevin Wolf , Beata Michalska , qemu-block@nongnu.org, qemu-devel@nongnu.org, Max Reitz , Keith Busch , Javier Gonzalez Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Tue, 2020-03-31 at 07:39 +0200, Klaus Birkelund Jensen wrote: > On Mar 25 12:38, Maxim Levitsky wrote: > > On Mon, 2020-03-16 at 07:28 -0700, Klaus Jensen wrote: > > > From: Klaus Jensen > > > > > > Pull the controller memory buffer check to its own function. The check > > > will be used on its own in later patches. > > > > > > Signed-off-by: Klaus Jensen > > > Acked-by: Keith Busch > > > --- > > > hw/block/nvme.c | 16 ++++++++++++---- > > > 1 file changed, 12 insertions(+), 4 deletions(-) > > > > > > diff --git a/hw/block/nvme.c b/hw/block/nvme.c > > > index b38d7e548a60..08a83d449de3 100644 > > > --- a/hw/block/nvme.c > > > +++ b/hw/block/nvme.c > > > @@ -52,14 +52,22 @@ > > > > > > static void nvme_process_sq(void *opaque); > > > > > > +static inline bool nvme_addr_is_cmb(NvmeCtrl *n, hwaddr addr) > > > +{ > > > + hwaddr low = n->ctrl_mem.addr; > > > + hwaddr hi = n->ctrl_mem.addr + int128_get64(n->ctrl_mem.size); > > > + > > > + return addr >= low && addr < hi; > > > +} > > > + > > > static void nvme_addr_read(NvmeCtrl *n, hwaddr addr, void *buf, int size) > > > { > > > - if (n->cmbsz && addr >= n->ctrl_mem.addr && > > > - addr < (n->ctrl_mem.addr + int128_get64(n->ctrl_mem.size))) { > > > + if (n->cmbsz && nvme_addr_is_cmb(n, addr)) { > > > memcpy(buf, (void *)&n->cmbuf[addr - n->ctrl_mem.addr], size); > > > - } else { > > > - pci_dma_read(&n->parent_obj, addr, buf, size); > > > + return; > > > } > > > + > > > + pci_dma_read(&n->parent_obj, addr, buf, size); > > > } > > > > > > static int nvme_check_sqid(NvmeCtrl *n, uint16_t sqid) > > > > Note that this patch still contains a bug that it removes the check against the accessed > > size, which you fix in later patch. > > I prefer to not add a bug in first place > > However if you have a reason for this, I won't mind. > > > > So yeah. The resons is that there is actually no bug at this point > because the controller only supports PRPs. I actually thought there was > a bug as well and reported it to qemu-security some months ago as a > potential out of bounds access. I was then schooled by Keith on how PRPs > work ;) Below is a paraphrased version of Keiths analysis. > > The PRPs does not cross page boundaries: True > > trans_len = n->page_size - (prp1 % n->page_size); > > The PRPs are always verified to be page aligned: True > > if (unlikely(!prp_ent || prp_ent & (n->page_size - 1))) { > > and the transfer length wont go above page size. So, since the beginning > of the address is within the CMB and considering that the CMB is of an > MB aligned and sized granularity, then we can never cross outside it > with PRPs. I understand now, however the reason I am arguing about this is that this patch actually _removes_ the size bound check It was before the patch: n->cmbsz && addr >= n->ctrl_mem.addr && addr < (n->ctrl_mem.addr + int128_get64(n->ctrl_mem.size) > > I could add the check at this point (because it *is* needed for when > SGLs are introduced), but I think it would just be noise and I would > need to explain why the check is there, but not really needed at this > point. Instead I'm adding a new patch before the SGL patch that explains > this. Best regards, Maxim Levitsky