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 DD31AC433E0 for ; Mon, 29 Jun 2020 20:47:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BD68E20724 for ; Mon, 29 Jun 2020 20:47:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1593463624; bh=Pu/0To4uEisqeiZLoEdchRbUIf4ajQDQZCMPElPY+rQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=mT/ab6wpO7Xy2YWFUEq8gZzuC/XWFT9UHQO35nkMXsqQUq340ixMhfEXgVbFXoxgN EGqZw+iIeRIWXB/sTej0xu7/kOZFAs9kkk3pDUgajt88pzjmZFTE5JGWePmWXMYQZ3 30cWcmlWm6g2f8/91ymZKJpncbHeMS3A52vDfyJg= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732515AbgF2UrD (ORCPT ); Mon, 29 Jun 2020 16:47:03 -0400 Received: from mail-wr1-f65.google.com ([209.85.221.65]:35671 "EHLO mail-wr1-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732940AbgF2Uq5 (ORCPT ); Mon, 29 Jun 2020 16:46:57 -0400 Received: by mail-wr1-f65.google.com with SMTP id g18so17996675wrm.2; Mon, 29 Jun 2020 13:46:55 -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=7B3b2pBNzZdwKMzrzlsX2I3eoakSivJkPodIWcuujkg=; b=fW+SnvRyi7VKbM8KtWX/EO15B0SBjRffG/Odue+cS1UymPPA8k6eW3mSzqFiITb2u0 Gocix24S1s+ZcZDMNepQRf7+gxj1u358NYhWXrFihe3I7mWc2/n7R9B1VA8L2rX6zjxa Xp3FYzuQloJ2ovpAFmOOoe6FtSPKljIRdAaxBQk9emnaacet3SiAwd3PFkKE/Fx3K4W2 VQ1nXmFgGk2MnQC7Zhj0ZWbiX6dNboENmZ/MxE/7ESOzV9m/F2dIZUPWbwTqmlTmQftp TV+LXmLZNzCky+c51f6yFf/iGsusFC9859cRMM02AJ11R+xqrYsB5J+WFoe6+wfsWX08 7D1A== X-Gm-Message-State: AOAM530wbfzhxTw/C91C0IkQfXp8I8xI8UqKJ4yYyshiulB80EFcTR2N lp81RfZlTNuh3BX0wZ33UgM= X-Google-Smtp-Source: ABdhPJyTQzsvY9UTZXZpGaoSPj9qQo2aDDpJP8RGi6+4kz9ZQ+mhGEvD1IWlImXuk16Q5SQVGOWyTQ== X-Received: by 2002:adf:f20a:: with SMTP id p10mr19802378wro.41.1593463615117; Mon, 29 Jun 2020 13:46:55 -0700 (PDT) Received: from liuwe-devbox-debian-v2 ([51.145.34.42]) by smtp.gmail.com with ESMTPSA id z2sm1152694wmc.2.2020.06.29.13.46.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 29 Jun 2020 13:46:54 -0700 (PDT) Date: Mon, 29 Jun 2020 20:46:53 +0000 From: Wei Liu To: t-mabelt@microsoft.com Cc: kys@microsoft.com, haiyangz@microsoft.com, sthemmin@microsoft.com, wei.liu@kernel.org, linux-hyperv@vger.kernel.org, linux-kernel@vger.kernel.org, mikelley@microsoft.com, parri.andrea@gmail.com, Andres Beltran Subject: Re: [PATCH v2 1/3] Drivers: hv: vmbus: Add vmbus_requestor data structure for VMBus hardening Message-ID: <20200629204653.o6q3a2fufgq62pzo@liuwe-devbox-debian-v2> References: <20200629200227.1518784-1-lkmlabelt@gmail.com> <20200629200227.1518784-2-lkmlabelt@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200629200227.1518784-2-lkmlabelt@gmail.com> 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 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.