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

Haitao Huang
2020-09-14T02:58:24Z

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?

> + if (ret)
> + break;

Some error cases here are fatal and should be passed back to user space so
that it would not retry.

> + }
> +
> + if (copy_to_user(arg, &addp, sizeof(addp)))
> + return -EFAULT;

This copy no longer needed?

> + return c;
> +}
> +

Thanks
Haitao