linux-kernel - RE: [RFC PATCH 3/9] x86/sgx: Allow userspace to add multiple pages in single ioctl()

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Message-ID: <960B34DE67B9E140824F1DCDEC400C0F654ECBBD@ORSMSX116.amr.corp.intel.com>
Date:   Mon, 3 Jun 2019 06:26:09 +0000
From:   "Xing, Cedric" <cedric.xing@...el.com>
To:     "Christopherson, Sean J" <sean.j.christopherson@...el.com>,
        "Jarkko Sakkinen" <jarkko.sakkinen@...ux.intel.com>
CC:     Andy Lutomirski <luto@...nel.org>,
        Stephen Smalley <sds@...ho.nsa.gov>,
        James Morris <jmorris@...ei.org>,
        "Serge E . Hallyn" <serge@...lyn.com>,
        LSM List <linux-security-module@...r.kernel.org>,
        Paul Moore <paul@...l-moore.com>,
        Eric Paris <eparis@...isplace.org>,
        "selinux@...r.kernel.org" <selinux@...r.kernel.org>,
        Jethro Beekman <jethro@...tanix.com>,
        "Hansen, Dave" <dave.hansen@...el.com>,
        "Thomas Gleixner" <tglx@...utronix.de>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>, X86 ML <x86@...nel.org>,
        "linux-sgx@...r.kernel.org" <linux-sgx@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "nhorman@...hat.com" <nhorman@...hat.com>,
        "npmccallum@...hat.com" <npmccallum@...hat.com>,
        "Ayoun, Serge" <serge.ayoun@...el.com>,
        "Katz-zamir, Shay" <shay.katz-zamir@...el.com>,
        "Huang, Haitao" <haitao.huang@...el.com>,
        "Andy Shevchenko" <andriy.shevchenko@...ux.intel.com>,
        "Svahn, Kai" <kai.svahn@...el.com>, Borislav Petkov <bp@...en8.de>,
        Josh Triplett <josh@...htriplett.org>,
        "Huang, Kai" <kai.huang@...el.com>,
        David Rientjes <rientjes@...gle.com>,
        "Roberts, William C" <william.c.roberts@...el.com>,
        "Tricca, Philip B" <philip.b.tricca@...el.com>
Subject: RE: [RFC PATCH 3/9] x86/sgx: Allow userspace to add multiple pages
 in single ioctl()

> From: Christopherson, Sean J
> Sent: Friday, May 31, 2019 4:32 PM
> 
> +/**
> + * sgx_ioc_enclave_add_pages - handler for %SGX_IOC_ENCLAVE_ADD_PAGES
> + *
> + * @filep:	open file to /dev/sgx
> + * @cmd:	the command value
> + * @arg:	pointer to an &sgx_enclave_add_page instance
> + *
> + * Add a range of pages to an uninitialized enclave (EADD), and
> +optionally
> + * extend the enclave's measurement with the contents of the page (EEXTEND).
> + * The range of pages must be virtually contiguous.  The SECINFO and
> + * measurement maskare applied to all pages, i.e. pages with different
> + * properties must be added in separate calls.
> + *
> + * EADD and EEXTEND are done asynchronously via worker threads.  A
> +successful
> + * sgx_ioc_enclave_add_page() only indicates the pages have been added
> +to the
> + * work queue, it does not guarantee adding the pages to the enclave
> +will
> + * succeed.
> + *
> + * Return:
> + *   0 on success,
> + *   -errno otherwise
> + */
> +static long sgx_ioc_enclave_add_pages(struct file *filep, unsigned int cmd,
> +				      unsigned long arg)
> +{
> +	struct sgx_enclave_add_pages *addp = (void *)arg;
> +	struct sgx_encl *encl = filep->private_data;
> +	struct sgx_secinfo secinfo;
> +	unsigned int i;
> +	int ret;
> +
> +	if (copy_from_user(&secinfo, (void __user *)addp->secinfo,
> +			   sizeof(secinfo)))
> +		return -EFAULT;
> +
> +	for (i = 0, ret = 0; i < addp->nr_pages && !ret; i++) {
> +		if (signal_pending(current))
> +			return -ERESTARTSYS;

If interrupted, how would user mode code know how many pages have been EADD'ed?

> +
> +		if (need_resched())
> +			cond_resched();
> +
> +		ret = sgx_encl_add_page(encl, addp->addr + i*PAGE_SIZE,
> +					addp->src + i*PAGE_SIZE,
> +					&secinfo, addp->mrmask);
> +	}
>  	return ret;
>  }
> 
> @@ -823,8 +845,8 @@ long sgx_ioctl(struct file *filep, unsigned int cmd, unsigned long arg)
>  	case SGX_IOC_ENCLAVE_CREATE:
>  		handler = sgx_ioc_enclave_create;
>  		break;
> -	case SGX_IOC_ENCLAVE_ADD_PAGE:
> -		handler = sgx_ioc_enclave_add_page;
> +	case SGX_IOC_ENCLAVE_ADD_PAGES:
> +		handler = sgx_ioc_enclave_add_pages;
>  		break;
>  	case SGX_IOC_ENCLAVE_INIT:
>  		handler = sgx_ioc_enclave_init;
> --
> 2.21.0