Re: [PATCH v38 12/24] x86/sgx: Add SGX_IOC_ENCLAVE_CREATE

["Haitao Huang" <haitao.huang@linux.intel.com>]

On Tue, 15 Sep 2020 06:28:30 -0500, Jarkko Sakkinen  
<jarkko.sakkinen@linux.intel.com> wrote:

> Add an ioctl that performs ENCLS[ECREATE], which creates SGX Enclave
> Control Structure for the enclave. SECS contains attributes about the
> enclave that are used by the hardware and cannot be directly accessed by
> software, as SECS resides in the EPC.
>
> One essential field in SECS is a field that stores the SHA256 of the
> measured enclave pages. This field, MRENCLAVE, is initialized by the
> ECREATE instruction and updated by every EADD and EEXTEND operation.
> Finally, EINIT locks down the value.
>
> Acked-by: Jethro Beekman <jethro@fortanix.com>
> Tested-by: Jethro Beekman <jethro@fortanix.com>
> Tested-by: Haitao Huang <haitao.huang@linux.intel.com>
> Tested-by: Chunyang Hui <sanqian.hcy@antfin.com>
> Tested-by: Jordan Hand <jorhand@linux.microsoft.com>
> Tested-by: Nathaniel McCallum <npmccallum@redhat.com>
> Tested-by: Seth Moore <sethmo@google.com>
> Tested-by: Darren Kenny <darren.kenny@oracle.com>
> Reviewed-by: Darren Kenny <darren.kenny@oracle.com>
> Co-developed-by: Sean Christopherson <sean.j.christopherson@intel.com>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
> Co-developed-by: Suresh Siddha <suresh.b.siddha@intel.com>
> Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
> Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
> ---
>  .../userspace-api/ioctl/ioctl-number.rst      |   1 +
>  arch/x86/include/uapi/asm/sgx.h               |  25 ++
>  arch/x86/kernel/cpu/sgx/Makefile              |   1 +
>  arch/x86/kernel/cpu/sgx/driver.c              |  12 +
>  arch/x86/kernel/cpu/sgx/driver.h              |   1 +
>  arch/x86/kernel/cpu/sgx/ioctl.c               | 220 ++++++++++++++++++
>  6 files changed, 260 insertions(+)
>  create mode 100644 arch/x86/include/uapi/asm/sgx.h
>  create mode 100644 arch/x86/kernel/cpu/sgx/ioctl.c
>
> diff --git a/Documentation/userspace-api/ioctl/ioctl-number.rst  
> b/Documentation/userspace-api/ioctl/ioctl-number.rst
> index 2a198838fca9..a89e1c46a25a 100644
> --- a/Documentation/userspace-api/ioctl/ioctl-number.rst
> +++ b/Documentation/userspace-api/ioctl/ioctl-number.rst
> @@ -323,6 +323,7 @@ Code  Seq#    Include  
> File                                           Comments
>                                                                       <mailto:tlewis@mindspring.com>
>  0xA3  90-9F  linux/dtlk.h
>  0xA4  00-1F  uapi/linux/tee.h                                         
> Generic TEE subsystem
> +0xA4  00-1F  uapi/asm/sgx.h                                           
> <mailto:linux-sgx@vger.kernel.org>
>  0xAA  00-3F  linux/uapi/linux/userfaultfd.h
>  0xAB  00-1F  linux/nbd.h
>  0xAC  00-1F  linux/raw.h
> diff --git a/arch/x86/include/uapi/asm/sgx.h  
> b/arch/x86/include/uapi/asm/sgx.h
> new file mode 100644
> index 000000000000..c75b375f3770
> --- /dev/null
> +++ b/arch/x86/include/uapi/asm/sgx.h
> @@ -0,0 +1,25 @@
> +/* SPDX-License-Identifier: ((GPL-2.0+ WITH Linux-syscall-note) OR  
> BSD-3-Clause) */
> +/*
> + * Copyright(c) 2016-19 Intel Corporation.
> + */
> +#ifndef _UAPI_ASM_X86_SGX_H
> +#define _UAPI_ASM_X86_SGX_H
> +
> +#include <linux/types.h>
> +#include <linux/ioctl.h>
> +
> +#define SGX_MAGIC 0xA4
> +
> +#define SGX_IOC_ENCLAVE_CREATE \
> +	_IOW(SGX_MAGIC, 0x00, struct sgx_enclave_create)
> +
> +/**
> + * struct sgx_enclave_create - parameter structure for the
> + *                             %SGX_IOC_ENCLAVE_CREATE ioctl
> + * @src:	address for the SECS page data
> + */
> +struct sgx_enclave_create  {
> +	__u64	src;
> +};
> +
> +#endif /* _UAPI_ASM_X86_SGX_H */
> diff --git a/arch/x86/kernel/cpu/sgx/Makefile  
> b/arch/x86/kernel/cpu/sgx/Makefile
> index 3fc451120735..91d3dc784a29 100644
> --- a/arch/x86/kernel/cpu/sgx/Makefile
> +++ b/arch/x86/kernel/cpu/sgx/Makefile
> @@ -1,4 +1,5 @@
>  obj-y += \
>  	driver.o \
>  	encl.o \
> +	ioctl.o \
>  	main.o
> diff --git a/arch/x86/kernel/cpu/sgx/driver.c  
> b/arch/x86/kernel/cpu/sgx/driver.c
> index f54da5f19c2b..7bdb49dfcca6 100644
> --- a/arch/x86/kernel/cpu/sgx/driver.c
> +++ b/arch/x86/kernel/cpu/sgx/driver.c
> @@ -114,10 +114,22 @@ static unsigned long sgx_get_unmapped_area(struct  
> file *file,
>  	return current->mm->get_unmapped_area(file, addr, len, pgoff, flags);
>  }
> +#ifdef CONFIG_COMPAT
> +static long sgx_compat_ioctl(struct file *filep, unsigned int cmd,
> +			      unsigned long arg)
> +{
> +	return sgx_ioctl(filep, cmd, arg);
> +}
> +#endif
> +
>  static const struct file_operations sgx_encl_fops = {
>  	.owner			= THIS_MODULE,
>  	.open			= sgx_open,
>  	.release		= sgx_release,
> +	.unlocked_ioctl		= sgx_ioctl,
> +#ifdef CONFIG_COMPAT
> +	.compat_ioctl		= sgx_compat_ioctl,
> +#endif
>  	.mmap			= sgx_mmap,
>  	.get_unmapped_area	= sgx_get_unmapped_area,
>  };
> diff --git a/arch/x86/kernel/cpu/sgx/driver.h  
> b/arch/x86/kernel/cpu/sgx/driver.h
> index f7ce40dedc91..e4063923115b 100644
> --- a/arch/x86/kernel/cpu/sgx/driver.h
> +++ b/arch/x86/kernel/cpu/sgx/driver.h
> @@ -9,6 +9,7 @@
>  #include <linux/rwsem.h>
>  #include <linux/sched.h>
>  #include <linux/workqueue.h>
> +#include <uapi/asm/sgx.h>
>  #include "sgx.h"
> #define SGX_EINIT_SPIN_COUNT	20
> diff --git a/arch/x86/kernel/cpu/sgx/ioctl.c  
> b/arch/x86/kernel/cpu/sgx/ioctl.c
> new file mode 100644
> index 000000000000..352a3c461812
> --- /dev/null
> +++ b/arch/x86/kernel/cpu/sgx/ioctl.c
> @@ -0,0 +1,220 @@
> +// SPDX-License-Identifier: (GPL-2.0 OR BSD-3-Clause)
> +// Copyright(c) 2016-19 Intel Corporation.
> +
> +#include <asm/mman.h>
> +#include <linux/mman.h>
> +#include <linux/delay.h>
> +#include <linux/file.h>
> +#include <linux/hashtable.h>
> +#include <linux/highmem.h>
> +#include <linux/ratelimit.h>
> +#include <linux/sched/signal.h>
> +#include <linux/shmem_fs.h>
> +#include <linux/slab.h>
> +#include <linux/suspend.h>
> +#include "driver.h"
> +#include "encl.h"
> +#include "encls.h"
> +
> +static u32 sgx_calc_ssa_frame_size(u32 miscselect, u64 xfrm)
> +{
> +	u32 size_max = PAGE_SIZE;
> +	u32 size;
> +	int i;
> +
> +	for (i = 2; i < 64; i++) {
> +		if (!((1 << i) & xfrm))
> +			continue;
> +
> +		size = SGX_SSA_GPRS_SIZE + sgx_xsave_size_tbl[i];
> +
> +		if (miscselect & SGX_MISC_EXINFO)
> +			size += SGX_SSA_MISC_EXINFO_SIZE;
> +
> +		if (size > size_max)
> +			size_max = size;
> +	}
> +
> +	return PFN_UP(size_max);
> +}
> +
> +static int sgx_validate_secs(const struct sgx_secs *secs)
> +{
> +	u64 max_size = (secs->attributes & SGX_ATTR_MODE64BIT) ?
> +		       sgx_encl_size_max_64 : sgx_encl_size_max_32;
> +
> +	if (secs->size < (2 * PAGE_SIZE) || !is_power_of_2(secs->size))
> +		return -EINVAL;
> +
> +	if (secs->base & (secs->size - 1))
> +		return -EINVAL;
> +
> +	if (secs->miscselect & sgx_misc_reserved_mask ||
> +	    secs->attributes & sgx_attributes_reserved_mask ||
> +	    secs->xfrm & sgx_xfrm_reserved_mask)
> +		return -EINVAL;
> +

Attributes should not be enforced against what's available on platform but  
checked and enforced against the mask for enforcement in sigstruct. For  
example an enclave could opt to sign with AVX bit in xfrm, but still be  
loadable on a platform without it if the sigstruct->body.attributes_mask  
does not turn that bit on.

Suggest to remove the above check,and do following during EINIt in  
sgx_encl_init:

-       /* Check that the required attributes have been authorized. */
+       /* Check that the requested attributes have been authorized. */
         if (encl->secs_attributes & ~encl->allowed_attributes)
                 return -EACCES;

+       /* Check that mandatory features are supported. */
+       if (sigstruct->body.attributes & sigstruct->body.attributes_mask &
+           sgx_attributes_reserved_mask)
+               return -EINVAL;
+       if (sigstruct->body.miscselect & sigstruct->body.misc_mask &
+           sgx_misc_reserved_mask)
+               return -EINVAL;
+       if (sigstruct->body.xfrm & sigstruct->body.xfrm_mask &
+           sgx_xfrm_reserved_mask)
+               return -EINVAL;
+
         ret = sgx_get_key_hash(sigstruct->modulus, mrsigner);

Haitao