[PATCH v23 12/24] x86/sgx: Linux Enclave Driver

[Stephen Smalley]

On 11/1/19 11:32 AM, Sean Christopherson wrote:
> On Fri, Nov 01, 2019 at 09:28:17AM -0400, Stephen Smalley wrote:
>> On 11/1/19 9:16 AM, Stephen Smalley wrote:
>>> So, IIUC, that means that merging the driver will create a regression with
>>> respect to LSM control over executable mappings that will only be
>>> rectified at some future point in time if/when someone submits LSM hooks
>>> or calls to existing hooks to restore such control.  That doesn't seem
>>> like a good idea.  Why can't you include at least that basic level of
>>> control now?  It is one thing to defer finer grained control or
>>> SGX-specific access controls to the future - that I can understand.  But
>>> introducing a regression in the existing controls is not really ok.
>>
>> Unless you are arguing that the existing checks on mmap/mprotect of
>> /dev/sgx/enclave are a coarse-grained approximation (effectively requiring
>> WX to the file or execmem for any user of SGX).
> 
> Yes, that's the argument as running any enclave will require RWX access to
> /dev/sgx/enclave.  EXECMEM won't trigger for SGX users as /dev/sgx/enclave
> must be MAP_SHARED and it's a non-private file (not backed by anonymous
> inode, in case I got the file terminology wrong).

Ok, so for SELinux's purposes, one will need to allow :file { open ioctl 
map read write execute } to whatever type is ultimately assigned to 
/dev/sgx/enclave in order to use SGX.