Re: [PATCH v37 13/24] x86/sgx: Add SGX_IOC_ENCLAVE_ADD_PAGES

Jarkko Sakkinen
2020-09-15T09:55:04Z

On Sun, Sep 13, 2020 at 09:56:03PM -0500, Haitao Huang wrote:
>
> On Fri, 11 Sep 2020 07:40:08 -0500, Jarkko Sakkinen
> <jarkko.sakkinen@linux.intel.com> wrote:
> ...
>
> > +/**
> > + * sgx_ioc_enclave_add_pages() - The handler for
> > %SGX_IOC_ENCLAVE_ADD_PAGES
> > + * @encl: an enclave pointer
> > + * @arg: a user pointer to a struct sgx_enclave_add_pages instance
> > + *
> > + * Add one or more pages to an uninitialized enclave, and optionally
> > extend the
> > + * measurement with the contents of the page. The SECINFO and
> > measurement mask
> > + * are applied to all pages.
> > + *
> > + * A SECINFO for a TCS is required to always contain zero permissions
> > because
> > + * CPU silently zeros them. Allowing anything else would cause a
> > mismatch in
> > + * the measurement.
> > + *
> > + * mmap()'s protection bits are capped by the page permissions. For
> > each page
> > + * address, the maximum protection bits are computed with the following
> > + * heuristics:
> > + *
> > + * 1. A regular page: PROT_R, PROT_W and PROT_X match the SECINFO
> > permissions.
> > + * 2. A TCS page: PROT_R | PROT_W.
> > + *
> > + * mmap() is not allowed to surpass the minimum of the maximum
> > protection bits
> > + * within the given address range.
> > + *
> > + * If ENCLS opcode fails, that effectively means that EPC has been
> > invalidated.
> > + * When this happens the enclave is destroyed and -EIO is returned to
> > the
> > + * caller.
> > + *
> > + * Return:
> > + * length of the data processed on success,
> > + * -EACCES if an executable source page is located in a noexec
> > partition,
> > + * -EIO if either ENCLS[EADD] or ENCLS[EEXTEND] fails
> > + * -errno otherwise
> > + */
> > +static long sgx_ioc_enclave_add_pages(struct sgx_encl *encl, void
> > __user *arg)
> > +{
> > + struct sgx_enclave_add_pages addp;
> > + struct sgx_secinfo secinfo;
> > + unsigned long c;
> > + int ret;
> > +
> > + if ((atomic_read(&encl->flags) & SGX_ENCL_INITIALIZED) ||
> > + !(atomic_read(&encl->flags) & SGX_ENCL_CREATED))
> > + return -EINVAL;
> > +
> > + if (copy_from_user(&addp, arg, sizeof(addp)))
> > + return -EFAULT;
> > +
> > + if (!IS_ALIGNED(addp.offset, PAGE_SIZE) ||
> > + !IS_ALIGNED(addp.src, PAGE_SIZE))
> > + return -EINVAL;
> > +
> > + if (!(access_ok(addp.src, PAGE_SIZE)))
> > + return -EFAULT;
> > +
> > + if (addp.length & (PAGE_SIZE - 1))
> > + return -EINVAL;
> > +
> > + if (addp.offset + addp.length - PAGE_SIZE >= encl->size)
> > + return -EINVAL;
> > +
> > + if (copy_from_user(&secinfo, (void __user *)addp.secinfo,
> > + sizeof(secinfo)))
> > + return -EFAULT;
> > +
> > + if (sgx_validate_secinfo(&secinfo))
> > + return -EINVAL;
> > +
> > + for (c = 0 ; c < addp.length; c += PAGE_SIZE) {
> > + if (c == SGX_MAX_ADD_PAGES_LENGTH || signal_pending(current)) {
> > + ret = c;
> > + break;
> > + }
> > +
> > + if (need_resched())
> > + cond_resched();
> > +
> > + ret = sgx_encl_add_page(encl, addp.src + c, addp.offset + c,
> > + addp.length - c, &secinfo, addp.flags);
>
> no need passing addp.length - c?

True, it is cruft from the past.

I'll remove.

>
> > + if (ret)
> > + break;
>
> Some error cases here are fatal and should be passed back to user space so
> that it would not retry.

I don't comprehend this. 'ret' is passed to the user space.

> > + }
> > +
> > + if (copy_to_user(arg, &addp, sizeof(addp)))
> > + return -EFAULT;
>
> This copy no longer needed?

True, it is cruft from the past.

I'll remove.

> > + return c;
> > +}
> > +
>
> Thanks
> Haitao

Thanks for the comments.

/Jarkko