Re: [RFC PATCH v3 2/4] x86/64: Call LSM hooks from SGX subsystem/module

[Sean Christopherson <sean.j.christopherson@xxxxxxxxx>]

On Sun, Jul 07, 2019 at 04:41:32PM -0700, Cedric Xing wrote:

...

> @@ -575,6 +576,46 @@ static int sgx_encl_add_page(struct sgx_encl *encl, unsigned long addr,
>  	return ret;
>  }
>  
> +static int sgx_encl_prepare_page(struct file *filp, unsigned long dst,
> +				 unsigned long src, void *buf)
> +{
> +	struct vm_area_struct *vma;
> +	unsigned long prot;
> +	int rc;
> +
> +	if (dst & ~PAGE_SIZE)
> +		return -EINVAL;
> +
> +	rc = down_read_killable(&current->mm->mmap_sem);
> +	if (rc)
> +		return rc;
> +
> +	vma = find_vma(current->mm, dst);
> +	if (vma && dst >= vma->vm_start)
> +		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);
> +	else
> +		prot = 0;
> +
> +	vma = find_vma(current->mm, src);
> +	if (!vma || src < vma->vm_start || src + PAGE_SIZE > vma->vm_end)
> +		rc = -EFAULT;
> +
> +	if (!rc && !(vma->vm_flags & VM_MAYEXEC))
> +		rc = -EACCES;

Disallowing loading enclave *data* from a noexec file system is an arbitrary
and weird restriction.

> +
> +	if (!rc && copy_from_user(buf, (void __user *)src, PAGE_SIZE))
> +		rc = -EFAULT;
> +
> +	if (!rc)
> +		rc = security_enclave_load(filp, dst, PAGE_SIZE, prot, vma);
> +
> +	up_read(&current->mm->mmap_sem);
> +
> +	return rc;
> +}