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=-8.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 C255AC433E0 for ; Mon, 29 Jun 2020 22:20:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8D6BC206E2 for ; Mon, 29 Jun 2020 22:20:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1593469245; bh=0XBoykD7FnEhnyRRXrAC2OIavqmfeMAECu3YZqmjMPg=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=VGlrMGxA19IrJPx1A/O7kyP/a71C2nN3Fy7/gOk6QsofQI8PFxhT2jD9UXWAo2KUi iBhgHELz4z2xNw++R/GIqt9qzkOyWTxq/WhqUE9+Z6j7htagkfmB2s5I7/+U/2Ygyv iPITfFzzMR4AzjV9UziiQw/uqCtbddiyxQoSv+oQ= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726746AbgF2WUp (ORCPT ); Mon, 29 Jun 2020 18:20:45 -0400 Received: from mail-wr1-f65.google.com ([209.85.221.65]:40611 "EHLO mail-wr1-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726068AbgF2WUp (ORCPT ); Mon, 29 Jun 2020 18:20:45 -0400 Received: by mail-wr1-f65.google.com with SMTP id h5so18149374wrc.7; Mon, 29 Jun 2020 15:20:42 -0700 (PDT) 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:user-agent; bh=oconLyfCCrFcK8XrG17EqC7K/s5rdGCuJ4yLxT0viwE=; b=jAwDK2JwFnwJC4S/07sr/zvE0uIl40f+cWJBR5fke6ceg4pKqumptA1O1hDaqVijFT XmkXRTA2kQW41/i6sLZQqbR5t/27HMGcrCrytVW2oT9oVtL4UEYki11pNbl9rPZzIT5C eQLtxyI0V5oNXmlMWws8IlS1QGGLBxYqRyDjflfpwHPHQrToGem0aSFG9F++LIyqbGf0 Fx2UrFo70ulwypZL9d3YM7x2gCC65fbcOkGAsTGZNnNPLOEALoKx0QP3bIhxEk2hAfHR W6UzcxCeCWDQj/6c+8giBmYN4vSFKViuhkOmKs9NEIz74UYTbNghdGiky29AYelvp+VG RtTg== X-Gm-Message-State: AOAM531pn7KZTEyV5z7q9EI8dKcwqMXGNXYf2hw6i+WLvRw3p01gKDuO bgmn2dru1a1W9/Ito/bjgdU= X-Google-Smtp-Source: ABdhPJxABby1hRCRpwmKQ9rs8fqBA8EMuqudnLCUV2rVxevP1Vw3NVLUNi5q7xD3zKna3AST4zhv+w== X-Received: by 2002:a5d:4986:: with SMTP id r6mr18245432wrq.424.1593469241812; Mon, 29 Jun 2020 15:20:41 -0700 (PDT) Received: from liuwe-devbox-debian-v2 ([51.145.34.42]) by smtp.gmail.com with ESMTPSA id c70sm1270784wme.32.2020.06.29.15.20.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 29 Jun 2020 15:20:41 -0700 (PDT) Date: Mon, 29 Jun 2020 22:20:40 +0000 From: Wei Liu To: Andres Beltran Cc: Wei Liu , Andres Beltran , kys@microsoft.com, haiyangz@microsoft.com, sthemmin@microsoft.com, linux-hyperv@vger.kernel.org, linux-kernel@vger.kernel.org, Michael Kelley , Andrea Parri Subject: Re: [PATCH v2 1/3] Drivers: hv: vmbus: Add vmbus_requestor data structure for VMBus hardening Message-ID: <20200629222040.bh7tkkridwt7sdlw@liuwe-devbox-debian-v2> References: <20200629200227.1518784-1-lkmlabelt@gmail.com> <20200629200227.1518784-2-lkmlabelt@gmail.com> <20200629204653.o6q3a2fufgq62pzo@liuwe-devbox-debian-v2> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20180716 Sender: linux-hyperv-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-hyperv@vger.kernel.org On Mon, Jun 29, 2020 at 05:51:05PM -0400, Andres Beltran wrote: > On Mon, Jun 29, 2020 at 4:46 PM Wei Liu wrote: > > > > On Mon, Jun 29, 2020 at 04:02:25PM -0400, Andres Beltran wrote: > > > Currently, VMbus drivers use pointers into guest memory as request IDs > > > for interactions with Hyper-V. To be more robust in the face of errors > > > or malicious behavior from a compromised Hyper-V, avoid exposing > > > guest memory addresses to Hyper-V. Also avoid Hyper-V giving back a > > > bad request ID that is then treated as the address of a guest data > > > structure with no validation. Instead, encapsulate these memory > > > addresses and provide small integers as request IDs. > > > > > > Signed-off-by: Andres Beltran > > > --- > > > Changes in v2: > > > - Get rid of "rqstor" variable in __vmbus_open(). > > > > > > drivers/hv/channel.c | 146 +++++++++++++++++++++++++++++++++++++++++ > > > include/linux/hyperv.h | 21 ++++++ > > > 2 files changed, 167 insertions(+) > > > > > > diff --git a/drivers/hv/channel.c b/drivers/hv/channel.c > > > index 3ebda7707e46..c89d57d0c2d2 100644 > > > --- a/drivers/hv/channel.c > > > +++ b/drivers/hv/channel.c > > > @@ -112,6 +112,70 @@ int vmbus_alloc_ring(struct vmbus_channel *newchannel, > > > } > > > EXPORT_SYMBOL_GPL(vmbus_alloc_ring); > > > > > > +/** > > > + * request_arr_init - Allocates memory for the requestor array. Each slot > > > + * keeps track of the next available slot in the array. Initially, each > > > + * slot points to the next one (as in a Linked List). The last slot > > > + * does not point to anything, so its value is U64_MAX by default. > > > + * @size The size of the array > > > + */ > > > +static u64 *request_arr_init(u32 size) > > > +{ > > > + int i; > > > + u64 *req_arr; > > > + > > > + req_arr = kcalloc(size, sizeof(u64), GFP_KERNEL); > > > + if (!req_arr) > > > + return NULL; > > > + > > > + for (i = 0; i < size - 1; i++) > > > + req_arr[i] = i + 1; > > > + > > > + /* Last slot (no more available slots) */ > > > + req_arr[i] = U64_MAX; > > > + > > > + return req_arr; > > > +} > > > + > > > +/* > > > + * vmbus_alloc_requestor - Initializes @rqstor's fields. > > > + * Slot at index 0 is the first free slot. > > > + * @size: Size of the requestor array > > > + */ > > > +static int vmbus_alloc_requestor(struct vmbus_requestor *rqstor, u32 size) > > > +{ > > > + u64 *rqst_arr; > > > + unsigned long *bitmap; > > > + > > > + rqst_arr = request_arr_init(size); > > > + if (!rqst_arr) > > > + return -ENOMEM; > > > + > > > + bitmap = bitmap_zalloc(size, GFP_KERNEL); > > > + if (!bitmap) { > > > + kfree(rqst_arr); > > > + return -ENOMEM; > > > + } > > > + > > > + rqstor->req_arr = rqst_arr; > > > + rqstor->req_bitmap = bitmap; > > > + rqstor->size = size; > > > + rqstor->next_request_id = 0; > > > + spin_lock_init(&rqstor->req_lock); > > > + > > > + return 0; > > > +} > > > + > > > +/* > > > + * vmbus_free_requestor - Frees memory allocated for @rqstor > > > + * @rqstor: Pointer to the requestor struct > > > + */ > > > +static void vmbus_free_requestor(struct vmbus_requestor *rqstor) > > > +{ > > > + kfree(rqstor->req_arr); > > > + bitmap_free(rqstor->req_bitmap); > > > +} > > > + > > > static int __vmbus_open(struct vmbus_channel *newchannel, > > > void *userdata, u32 userdatalen, > > > void (*onchannelcallback)(void *context), void *context) > > > @@ -132,6 +196,12 @@ static int __vmbus_open(struct vmbus_channel *newchannel, > > > if (newchannel->state != CHANNEL_OPEN_STATE) > > > return -EINVAL; > > > > > > + /* Create and init requestor */ > > > + if (newchannel->rqstor_size) { > > > + if (vmbus_alloc_requestor(&newchannel->requestor, newchannel->rqstor_size)) > > > + return -ENOMEM; > > > + } > > > + > > > > Sorry for not noticing this in the last round: this infrastructure is > > initialized conditionally but used unconditionally. > > > > I can think of two options here: > > > > 1. Mandate rqstor_size to be non-zero. Always initialize this > > infra. > > 2. Modify vmbus_next_request_id and vmbus_request_addr to deal with > > uninitialized state. > > > > For #2, you can simply check rqstor->size _before_ taking the lock > > (because it may be uninitialized, and the assumption is ->size will not > > change during the channel's lifetime, hence no lock is needed) and > > simply return the same value to the caller. > > > > Wei. > > Right. I think option #2 would be preferable in this case, because #1 works > if we had a default non-zero size for cases where rqstor_size has not been > set to a non-zero value before calling vmbus_alloc_requestor(). For #2, what > do you mean by "same value"? I think we would need to return > VMBUS_RQST_ERROR if the size is 0, because otherwise we would be > returning the same guest memory address which we don't want to expose. By "same value", I meant reverting back to using guest memory address. I thought downgrading gracefully is better than making the driver stop working. If exposing guest address is not acceptable, you can return VMBUS_RQST_ERROR -- but at the point you may as well mandate requestor infrastructure to be always initialized, right? Wei. > > Andres.