linux-kernel - Re: [PATCH 2/6] PCI: hv: Use vmbus_requestor to generate transaction IDs for VMbus hardening

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Message-ID: <20220408163411.GA206695@anparri>
Date:   Fri, 8 Apr 2022 18:34:11 +0200
From:   Andrea Parri <parri.andrea@...il.com>
To:     "Michael Kelley (LINUX)" <mikelley@...rosoft.com>
Cc:     KY Srinivasan <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Wei Liu <wei.liu@...nel.org>, Dexuan Cui <decui@...rosoft.com>,
        Wei Hu <weh@...rosoft.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Wilczynski <kw@...ux.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/6] PCI: hv: Use vmbus_requestor to generate transaction
 IDs for VMbus hardening

> > @@ -2743,11 +2751,14 @@ static void hv_pci_onchannelcallback(void *context)
> >  		switch (desc->type) {
> >  		case VM_PKT_COMP:
> > 
> > -			/*
> > -			 * The host is trusted, and thus it's safe to interpret
> > -			 * this transaction ID as a pointer.
> > -			 */
> > -			comp_packet = (struct pci_packet *)req_id;
> > +			req_addr = chan->request_addr_callback(chan, req_id);
> > +			if (req_addr == VMBUS_RQST_ERROR) {
> > +				dev_warn_ratelimited(&hbus->hdev->device,
> > +						     "Invalid transaction ID %llx\n",
> > +						     req_id);
> 
> This handling of a bad requestID error is a bit different from storvsc
> and netvsc.  They both use dev_err().  Earlier in the storvsc and netvsc
> cases, I remember some discussion about whether to rate limit these errors,
> and evidently we decided not to.  I think we should be consistent unless
> there's a specific reason not to.

Well, this 'error' is hardcoded in hv_compose_msi_msg() (as described in
patch #6).  But no strong opinion really: let me replace with dev_err().

Thanks,
  Andrea