linux-integrity.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Ross Philipson <ross.philipson@oracle.com>
To: Andy Lutomirski <luto@kernel.org>,
	Andi Kleen <ak@linux.intel.com>, Joerg Roedel <jroedel@suse.de>,
	Thomas Gleixner <tglx@linutronix.de>,
	Jason Wang <jasowang@redhat.com>,
	Andrew Cooper <andrew.cooper3@citrix.com>
Cc: Robin Murphy <robin.murphy@arm.com>,
	LKML <linux-kernel@vger.kernel.org>, X86 ML <x86@kernel.org>,
	iommu <iommu@lists.linux-foundation.org>,
	linux-integrity <linux-integrity@vger.kernel.org>,
	"open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
	"Daniel P. Smith" <dpsmith@apertussolutions.com>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	"H. Peter Anvin" <hpa@zytor.com>,
	trenchboot-devel@googlegroups.com
Subject: Re: [PATCH v2 12/12] iommu: Do not allow IOMMU passthrough with Secure Launch
Date: Wed, 30 Jun 2021 05:50:20 -0400	[thread overview]
Message-ID: <61f383bc-d582-418f-8d6b-4838bd0d912c@oracle.com> (raw)
In-Reply-To: <CALCETrUdEvLFKuvU7z_ut6cEfAgJogNp3oBXL-EdDLU=W+VeKA@mail.gmail.com>

On 6/21/21 5:15 PM, Andy Lutomirski wrote:
> On Mon, Jun 21, 2021 at 10:51 AM Ross Philipson
> <ross.philipson@oracle.com> wrote:
>>
>> On 6/18/21 2:32 PM, Robin Murphy wrote:
>>> On 2021-06-18 17:12, Ross Philipson wrote:
>>>> The IOMMU should always be set to default translated type after
>>>> the PMRs are disabled to protect the MLE from DMA.
>>>>
>>>> Signed-off-by: Ross Philipson <ross.philipson@oracle.com>
>>>> ---
>>>>    drivers/iommu/intel/iommu.c | 5 +++++
>>>>    drivers/iommu/iommu.c       | 6 +++++-
>>>>    2 files changed, 10 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
>>>> index be35284..4f0256d 100644
>>>> --- a/drivers/iommu/intel/iommu.c
>>>> +++ b/drivers/iommu/intel/iommu.c
>>>> @@ -41,6 +41,7 @@
>>>>    #include <linux/dma-direct.h>
>>>>    #include <linux/crash_dump.h>
>>>>    #include <linux/numa.h>
>>>> +#include <linux/slaunch.h>
>>>>    #include <asm/irq_remapping.h>
>>>>    #include <asm/cacheflush.h>
>>>>    #include <asm/iommu.h>
>>>> @@ -2877,6 +2878,10 @@ static bool device_is_rmrr_locked(struct device
>>>> *dev)
>>>>     */
>>>>    static int device_def_domain_type(struct device *dev)
>>>>    {
>>>> +    /* Do not allow identity domain when Secure Launch is configured */
>>>> +    if (slaunch_get_flags() & SL_FLAG_ACTIVE)
>>>> +        return IOMMU_DOMAIN_DMA;
>>>
>>> Is this specific to Intel? It seems like it could easily be done
>>> commonly like the check for untrusted external devices.
>>
>> It is currently Intel only but that will change. I will look into what
>> you suggest.
>>
>>>
>>>> +
>>>>        if (dev_is_pci(dev)) {
>>>>            struct pci_dev *pdev = to_pci_dev(dev);
>>>>    diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
>>>> index 808ab70d..d49b7dd 100644
>>>> --- a/drivers/iommu/iommu.c
>>>> +++ b/drivers/iommu/iommu.c
>>>> @@ -23,6 +23,7 @@
>>>>    #include <linux/property.h>
>>>>    #include <linux/fsl/mc.h>
>>>>    #include <linux/module.h>
>>>> +#include <linux/slaunch.h>
>>>>    #include <trace/events/iommu.h>
>>>>      static struct kset *iommu_group_kset;
>>>> @@ -2761,7 +2762,10 @@ void iommu_set_default_passthrough(bool cmd_line)
>>>>    {
>>>>        if (cmd_line)
>>>>            iommu_cmd_line |= IOMMU_CMD_LINE_DMA_API;
>>>> -    iommu_def_domain_type = IOMMU_DOMAIN_IDENTITY;
>>>> +
>>>> +    /* Do not allow identity domain when Secure Launch is configured */
>>>> +    if (!(slaunch_get_flags() & SL_FLAG_ACTIVE))
>>>> +        iommu_def_domain_type = IOMMU_DOMAIN_IDENTITY;
>>>
>>> Quietly ignoring the setting and possibly leaving iommu_def_domain_type
>>> uninitialised (note that 0 is not actually a usable type) doesn't seem
>>> great. AFAICS this probably warrants similar treatment to the
>>
>> Ok so I guess it would be better to set it to IOMMU_DOMAIN_DMA event
>> though passthrough was requested. Or perhaps something more is needed here?
>>
>>> mem_encrypt_active() case - there doesn't seem a great deal of value in
>>> trying to save users from themselves if they care about measured boot
>>> yet explicitly pass options which may compromise measured boot. If you
>>> really want to go down that route there's at least the sysfs interface
>>> you'd need to nobble as well, not to mention the various ways of
>>> completely disabling IOMMUs...
>>
>> Doing a secure launch with the kernel is not a general purpose user use
>> case. A lot of work is done to secure the environment. Allowing
>> passthrough mode would leave the secure launch kernel exposed to DMA. I
>> think what we are trying to do here is what we intend though there may
>> be a better way or perhaps it is incomplete as you suggest.
>>
> 
> I don't really like all these special cases.  Generically, what you're
> trying to do is (AFAICT) to get the kernel to run in a mode in which
> it does its best not to trust attached devices.  Nothing about this is
> specific to Secure Launch.  There are plenty of scenarios in which
> this the case:
> 
>   - Virtual devices in a VM host outside the TCB, e.g. VDUSE, Xen
> device domains (did I get the name right), whatever tricks QEMU has,
> etc.
>   - SRTM / DRTM technologies (including but not limited to Secure
> Launch -- plain old Secure Boot can work like this too).
>   - Secure guest technologies, including but not limited to TDX and SEV.
>   - Any computer with a USB-C port or other external DMA-capable port.
>   - Regular computers in which the admin wants to enable this mode for
> whatever reason.
> 
> Can you folks all please agree on a coordinated way for a Linux kernel
> to configure itself appropriately?  Or to be configured via initramfs,
> boot option, or some other trusted source of configuration supplied at
> boot time?  We don't need a whole bunch of if (TDX), if (SEV), if
> (secure launch), if (I have a USB-C port with PCIe exposed), if
> (running on Xen), and similar checks all over the place.
> 

I replied to Robin Murphy in another thread. As far as the IOMMU is 
concerned, I think we need to rethink our approach. As to the other 
technologies you mention here, we have not considered special casing 
anything at this point.

Thanks
Ross

  reply	other threads:[~2021-06-30  9:50 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-18 16:12 [PATCH v2 00/12] x86: Trenchboot secure dynamic launch Linux kernel support Ross Philipson
2021-06-18 16:12 ` [PATCH v2 01/12] x86/boot: Place kernel_info at a fixed offset Ross Philipson
2021-06-18 16:12 ` [PATCH v2 02/12] x86: Secure Launch Kconfig Ross Philipson
2021-06-18 16:12 ` [PATCH v2 03/12] x86: Secure Launch main header file Ross Philipson
2021-06-18 16:12 ` [PATCH v2 04/12] x86: Add early SHA support for Secure Launch early measurements Ross Philipson
2021-06-18 16:12 ` [PATCH v2 05/12] x86: Secure Launch kernel early boot stub Ross Philipson
2021-06-18 16:12 ` [PATCH v2 06/12] x86: Secure Launch kernel late " Ross Philipson
2021-06-18 16:12 ` [PATCH v2 07/12] x86: Secure Launch SMP bringup support Ross Philipson
2021-06-18 16:12 ` [PATCH v2 08/12] kexec: Secure Launch kexec SEXIT support Ross Philipson
2021-06-18 16:12 ` [PATCH v2 09/12] reboot: Secure Launch SEXIT support on reboot paths Ross Philipson
2021-06-18 16:12 ` [PATCH v2 10/12] x86: Secure Launch late initcall platform module Ross Philipson
2021-06-18 16:12 ` [PATCH v2 11/12] tpm: Allow locality 2 to be set when initializing the TPM for Secure Launch Ross Philipson
2021-06-18 16:12 ` [PATCH v2 12/12] iommu: Do not allow IOMMU passthrough with " Ross Philipson
2021-06-18 18:32   ` Robin Murphy
2021-06-21 17:51     ` Ross Philipson
2021-06-21 21:15       ` Andy Lutomirski
2021-06-30  9:50         ` Ross Philipson [this message]
2021-08-04  3:05         ` Daniel P. Smith
2021-06-22 11:06       ` Robin Murphy
2021-06-30  9:47         ` Ross Philipson

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=61f383bc-d582-418f-8d6b-4838bd0d912c@oracle.com \
    --to=ross.philipson@oracle.com \
    --cc=ak@linux.intel.com \
    --cc=andrew.cooper3@citrix.com \
    --cc=bp@alien8.de \
    --cc=dpsmith@apertussolutions.com \
    --cc=hpa@zytor.com \
    --cc=iommu@lists.linux-foundation.org \
    --cc=jasowang@redhat.com \
    --cc=jroedel@suse.de \
    --cc=linux-doc@vger.kernel.org \
    --cc=linux-integrity@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=luto@kernel.org \
    --cc=mingo@redhat.com \
    --cc=robin.murphy@arm.com \
    --cc=tglx@linutronix.de \
    --cc=trenchboot-devel@googlegroups.com \
    --cc=x86@kernel.org \
    --subject='Re: [PATCH v2 12/12] iommu: Do not allow IOMMU passthrough with Secure Launch' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).