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[PATCH v3 10/14] configfs-tsm: Allow the privlevel_floor attribute to be updated

Tom Lendacky posted 14 patches 1 year, 10 months ago
There is a newer version of this series
[PATCH v3 10/14] configfs-tsm: Allow the privlevel_floor attribute to be updated
Posted by Tom Lendacky 1 year, 10 months ago 
With the introduction of an SVSM, Linux will be running at a non-zero
VMPL. Any request for an attestation report at a higher priviledge VMPL
than what Linux is currently running will result in an error. Allow for
the privlevel_floor attribute to be updated dynamically so that the
attribute may be set dynamically.

Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
---
 drivers/virt/coco/sev-guest/sev-guest.c | 5 ++++-
 include/linux/tsm.h                     | 2 +-
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/virt/coco/sev-guest/sev-guest.c b/drivers/virt/coco/sev-guest/sev-guest.c
index 1ff897913bf4..bba6531cb606 100644
--- a/drivers/virt/coco/sev-guest/sev-guest.c
+++ b/drivers/virt/coco/sev-guest/sev-guest.c
@@ -885,7 +885,7 @@ static int sev_report_new(struct tsm_report *report, void *data)
 	return 0;
 }
 
-static const struct tsm_ops sev_tsm_ops = {
+static struct tsm_ops sev_tsm_ops = {
 	.name = KBUILD_MODNAME,
 	.report_new = sev_report_new,
 };
@@ -972,6 +972,9 @@ static int __init sev_guest_probe(struct platform_device *pdev)
 	snp_dev->input.resp_gpa = __pa(snp_dev->response);
 	snp_dev->input.data_gpa = __pa(snp_dev->certs_data);
 
+	/* Set the privlevel_floor attribute based on the current VMPL */
+	sev_tsm_ops.privlevel_floor = snp_get_vmpl();
+
 	ret = tsm_register(&sev_tsm_ops, snp_dev, &tsm_report_extra_type);
 	if (ret)
 		goto e_free_cert_data;
diff --git a/include/linux/tsm.h b/include/linux/tsm.h
index de8324a2223c..50c5769657d8 100644
--- a/include/linux/tsm.h
+++ b/include/linux/tsm.h
@@ -54,7 +54,7 @@ struct tsm_report {
  */
 struct tsm_ops {
 	const char *name;
-	const unsigned int privlevel_floor;
+	unsigned int privlevel_floor;
 	int (*report_new)(struct tsm_report *report, void *data);
 };
 
-- 
2.43.2
Re: [PATCH v3 10/14] configfs-tsm: Allow the privlevel_floor attribute to be updated
Posted by Dan Williams 1 year, 9 months ago 
Tom Lendacky wrote:
> With the introduction of an SVSM, Linux will be running at a non-zero
> VMPL. Any request for an attestation report at a higher priviledge VMPL
> than what Linux is currently running will result in an error. Allow for
> the privlevel_floor attribute to be updated dynamically so that the
> attribute may be set dynamically.
> 
> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
> ---
>  drivers/virt/coco/sev-guest/sev-guest.c | 5 ++++-
>  include/linux/tsm.h                     | 2 +-
>  2 files changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/virt/coco/sev-guest/sev-guest.c b/drivers/virt/coco/sev-guest/sev-guest.c
> index 1ff897913bf4..bba6531cb606 100644
> --- a/drivers/virt/coco/sev-guest/sev-guest.c
> +++ b/drivers/virt/coco/sev-guest/sev-guest.c
> @@ -885,7 +885,7 @@ static int sev_report_new(struct tsm_report *report, void *data)
>  	return 0;
>  }
>  
> -static const struct tsm_ops sev_tsm_ops = {
> +static struct tsm_ops sev_tsm_ops = {
>  	.name = KBUILD_MODNAME,
>  	.report_new = sev_report_new,
>  };
> @@ -972,6 +972,9 @@ static int __init sev_guest_probe(struct platform_device *pdev)
>  	snp_dev->input.resp_gpa = __pa(snp_dev->response);
>  	snp_dev->input.data_gpa = __pa(snp_dev->certs_data);
>  
> +	/* Set the privlevel_floor attribute based on the current VMPL */
> +	sev_tsm_ops.privlevel_floor = snp_get_vmpl();

Why is this not vmpck_id?
Re: [PATCH v3 10/14] configfs-tsm: Allow the privlevel_floor attribute to be updated
Posted by Tom Lendacky 1 year, 9 months ago 
On 4/15/24 23:55, Dan Williams wrote:
> Tom Lendacky wrote:
>> With the introduction of an SVSM, Linux will be running at a non-zero
>> VMPL. Any request for an attestation report at a higher priviledge VMPL
>> than what Linux is currently running will result in an error. Allow for
>> the privlevel_floor attribute to be updated dynamically so that the
>> attribute may be set dynamically.
>>
>> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
>> ---
>>   drivers/virt/coco/sev-guest/sev-guest.c | 5 ++++-
>>   include/linux/tsm.h                     | 2 +-
>>   2 files changed, 5 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/virt/coco/sev-guest/sev-guest.c b/drivers/virt/coco/sev-guest/sev-guest.c
>> index 1ff897913bf4..bba6531cb606 100644
>> --- a/drivers/virt/coco/sev-guest/sev-guest.c
>> +++ b/drivers/virt/coco/sev-guest/sev-guest.c
>> @@ -885,7 +885,7 @@ static int sev_report_new(struct tsm_report *report, void *data)
>>   	return 0;
>>   }
>>   
>> -static const struct tsm_ops sev_tsm_ops = {
>> +static struct tsm_ops sev_tsm_ops = {
>>   	.name = KBUILD_MODNAME,
>>   	.report_new = sev_report_new,
>>   };
>> @@ -972,6 +972,9 @@ static int __init sev_guest_probe(struct platform_device *pdev)
>>   	snp_dev->input.resp_gpa = __pa(snp_dev->response);
>>   	snp_dev->input.data_gpa = __pa(snp_dev->certs_data);
>>   
>> +	/* Set the privlevel_floor attribute based on the current VMPL */
>> +	sev_tsm_ops.privlevel_floor = snp_get_vmpl();
> 
> Why is this not vmpck_id?

Good catch, this probably should be pulled out separately and submitted 
as a Fixes: against the current support. If you think it's important 
enough, I can do that and put this at the beginning of the series. Or I 
can just modify this to use the vmpck_id value. Any preference?

Thanks,
Tom
Re: [PATCH v3 10/14] configfs-tsm: Allow the privlevel_floor attribute to be updated
Posted by Dan Williams 1 year, 9 months ago 
Tom Lendacky wrote:
> On 4/15/24 23:55, Dan Williams wrote:
> > Tom Lendacky wrote:
> >> With the introduction of an SVSM, Linux will be running at a non-zero
> >> VMPL. Any request for an attestation report at a higher priviledge VMPL
> >> than what Linux is currently running will result in an error. Allow for
> >> the privlevel_floor attribute to be updated dynamically so that the
> >> attribute may be set dynamically.
> >>
> >> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
> >> ---
> >>   drivers/virt/coco/sev-guest/sev-guest.c | 5 ++++-
> >>   include/linux/tsm.h                     | 2 +-
> >>   2 files changed, 5 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/drivers/virt/coco/sev-guest/sev-guest.c b/drivers/virt/coco/sev-guest/sev-guest.c
> >> index 1ff897913bf4..bba6531cb606 100644
> >> --- a/drivers/virt/coco/sev-guest/sev-guest.c
> >> +++ b/drivers/virt/coco/sev-guest/sev-guest.c
> >> @@ -885,7 +885,7 @@ static int sev_report_new(struct tsm_report *report, void *data)
> >>   	return 0;
> >>   }
> >>   
> >> -static const struct tsm_ops sev_tsm_ops = {
> >> +static struct tsm_ops sev_tsm_ops = {
> >>   	.name = KBUILD_MODNAME,
> >>   	.report_new = sev_report_new,
> >>   };
> >> @@ -972,6 +972,9 @@ static int __init sev_guest_probe(struct platform_device *pdev)
> >>   	snp_dev->input.resp_gpa = __pa(snp_dev->response);
> >>   	snp_dev->input.data_gpa = __pa(snp_dev->certs_data);
> >>   
> >> +	/* Set the privlevel_floor attribute based on the current VMPL */
> >> +	sev_tsm_ops.privlevel_floor = snp_get_vmpl();
> > 
> > Why is this not vmpck_id?
> 
> Good catch, this probably should be pulled out separately and submitted 
> as a Fixes: against the current support. If you think it's important 
> enough, I can do that and put this at the beginning of the series. Or I 
> can just modify this to use the vmpck_id value. Any preference?

I dunno, you tell me. What breaks if privlevel_floor is mismatched vs
vmpl and/or vmpck_id? If it warrants a "Fixes:" it should probably be
broken out.

However, I *guess* it is just adding some sanity checking precision to
userspace requests and makes some input validation not catch errors when
userspace tries to generate reports from the wrong level, right? I.e.
privlevel_floor may be lower than expected, but userspace should not be
depending on that since the report generation will fail.
Re: [PATCH v3 10/14] configfs-tsm: Allow the privlevel_floor attribute to be updated
Posted by Tom Lendacky 1 year, 9 months ago 
On 4/16/24 10:57, Dan Williams wrote:
> Tom Lendacky wrote:
>> On 4/15/24 23:55, Dan Williams wrote:
>>> Tom Lendacky wrote:
>>>> With the introduction of an SVSM, Linux will be running at a non-zero
>>>> VMPL. Any request for an attestation report at a higher priviledge VMPL
>>>> than what Linux is currently running will result in an error. Allow for
>>>> the privlevel_floor attribute to be updated dynamically so that the
>>>> attribute may be set dynamically.
>>>>
>>>> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
>>>> ---
>>>>    drivers/virt/coco/sev-guest/sev-guest.c | 5 ++++-
>>>>    include/linux/tsm.h                     | 2 +-
>>>>    2 files changed, 5 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/drivers/virt/coco/sev-guest/sev-guest.c b/drivers/virt/coco/sev-guest/sev-guest.c
>>>> index 1ff897913bf4..bba6531cb606 100644
>>>> --- a/drivers/virt/coco/sev-guest/sev-guest.c
>>>> +++ b/drivers/virt/coco/sev-guest/sev-guest.c
>>>> @@ -885,7 +885,7 @@ static int sev_report_new(struct tsm_report *report, void *data)
>>>>    	return 0;
>>>>    }
>>>>    
>>>> -static const struct tsm_ops sev_tsm_ops = {
>>>> +static struct tsm_ops sev_tsm_ops = {
>>>>    	.name = KBUILD_MODNAME,
>>>>    	.report_new = sev_report_new,
>>>>    };
>>>> @@ -972,6 +972,9 @@ static int __init sev_guest_probe(struct platform_device *pdev)
>>>>    	snp_dev->input.resp_gpa = __pa(snp_dev->response);
>>>>    	snp_dev->input.data_gpa = __pa(snp_dev->certs_data);
>>>>    
>>>> +	/* Set the privlevel_floor attribute based on the current VMPL */
>>>> +	sev_tsm_ops.privlevel_floor = snp_get_vmpl();
>>>
>>> Why is this not vmpck_id?
>>
>> Good catch, this probably should be pulled out separately and submitted
>> as a Fixes: against the current support. If you think it's important
>> enough, I can do that and put this at the beginning of the series. Or I
>> can just modify this to use the vmpck_id value. Any preference?
> 
> I dunno, you tell me. What breaks if privlevel_floor is mismatched vs
> vmpl and/or vmpck_id? If it warrants a "Fixes:" it should probably be
> broken out.
> 
> However, I *guess* it is just adding some sanity checking precision to
> userspace requests and makes some input validation not catch errors when
> userspace tries to generate reports from the wrong level, right? I.e.
> privlevel_floor may be lower than expected, but userspace should not be
> depending on that since the report generation will fail.

Yeah, it just results in a different type of error. If the VMPL 
specified by the user is numerically lower than the vmpck_id, then the 
request will fail with a specific return code value. With the change to 
privlevel_floor to use vmpck_id, then you would just get the error that 
much sooner when trying to set a value that is lower than the floor.

Since I don't think the vmpck_id module parameter is a common case 
today, let's just leave that change in this patch.

Thanks,
Tom

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