[RFC PATCH v4 12/12] LSM: x86/sgx: Show line of sight to LSM support SGX2's EAUG

[Sean Christopherson]

On Fri, Jun 21, 2019 at 10:18:55AM -0700, Xing, Cedric wrote:
> > From: Christopherson, Sean J
> > Sent: Wednesday, June 19, 2019 3:24 PM
> > 
> > diff --git a/arch/x86/kernel/cpu/sgx/driver/main.c b/arch/x86/kernel/cpu/sgx/driver/main.c
> > index 4379a2fb1f82..b478c0f45279 100644
> > --- a/arch/x86/kernel/cpu/sgx/driver/main.c
> > +++ b/arch/x86/kernel/cpu/sgx/driver/main.c
> > @@ -99,7 +99,8 @@ static long sgx_compat_ioctl(struct file *filep, unsigned int cmd,
> >   * page is considered to have no RWX permissions, i.e. is inaccessible.
> >   */
> >  static unsigned long sgx_allowed_rwx(struct sgx_encl *encl,
> > -				     struct vm_area_struct *vma)
> > +				     struct vm_area_struct *vma,
> > +				     bool *eaug)
> >  {
> >  	unsigned long allowed_rwx = VM_READ | VM_WRITE | VM_EXEC;
> >  	unsigned long idx, idx_start, idx_end; @@ -123,6 +124,8 @@ static unsigned long
> > sgx_allowed_rwx(struct sgx_encl *encl,
> >  			allowed_rwx = 0;
> >  		else
> >  			allowed_rwx &= page->vm_prot_bits;
> > +		if (page->vm_prot_bits & SGX_VM_EAUG)
> > +			*eaug = true;
> >  		if (!allowed_rwx)
> >  			break;
> >  	}
> > @@ -134,16 +137,17 @@ static int sgx_mmap(struct file *file, struct vm_area_struct *vma)
> > {
> >  	struct sgx_encl *encl = file->private_data;
> >  	unsigned long allowed_rwx, prot;
> > +	bool eaug = false;
> >  	int ret;
> > 
> > -	allowed_rwx = sgx_allowed_rwx(encl, vma);
> > +	allowed_rwx = sgx_allowed_rwx(encl, vma, &eaug);
> >  	if (vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC) & ~allowed_rwx)
> >  		return -EACCES;
> 
> IIUC, "eaug range" has to be mapped PROT_NONE, then vm_ops->fault() won't be
> invoked. Am I correct? Then how to EAUG on #PF?

Pages tagged SGX_VM_EAUG also have maximal permissions and can be mapped
PROT_{READ,WRITE,EXEC} accordingly.

> 
> > 
> >  	prot = _calc_vm_trans(vma->vm_flags, VM_READ, PROT_READ) |
> >  	       _calc_vm_trans(vma->vm_flags, VM_WRITE, PROT_WRITE) |
> >  	       _calc_vm_trans(vma->vm_flags, VM_EXEC, PROT_EXEC);
> > -	ret = security_enclave_map(prot);
> > +	ret = security_enclave_map(prot, eaug);
> >  	if (ret)
> >  		return ret;
> >