Re: [PATCH] x86/sgx: Refine rollback in SGX_IOC_ENCLAVE_ADD_PAGE

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

On Fri, 18 Sep 2020 08:02:26 -0500, Jarkko Sakkinen  
<jarkko.sakkinen@linux.intel.com> wrote:

> Revert back 'count' to struct sgx_enclave_add_pages as in most of the
> cases enclave can be recovered. Refine the documentation to better
> describe the enclave is persisted.
>
> Move the check for -EIO from sgx_encl_add_page() to
> sgx_ioc_enclave_pages() to make it more visible. It was quite
> hidden over there.
>
> Cc: Sean Christopherson <sean.j.christopherson@intel.com>
> Cc: Haitao Huang <haitao.huang@linux.intel.com>
> Cc: Borislav Petkov <bp@alien8.de>
> Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
> ---
>  arch/x86/include/uapi/asm/sgx.h | 12 +++++++-----
>  arch/x86/kernel/cpu/sgx/ioctl.c | 29 ++++++++++++++---------------
>  2 files changed, 21 insertions(+), 20 deletions(-)
>
> diff --git a/arch/x86/include/uapi/asm/sgx.h  
> b/arch/x86/include/uapi/asm/sgx.h
> index 1564d7f88597..ec5157b2ff50 100644
> --- a/arch/x86/include/uapi/asm/sgx.h
> +++ b/arch/x86/include/uapi/asm/sgx.h
> @@ -45,13 +45,15 @@ struct sgx_enclave_create  {
>   * @length:	length of the data (multiple of the page size)
>   * @secinfo:	address for the SECINFO data
>   * @flags:	page control flags
> + * @count:	number of bytes added (multiple of the page size)
>   */
>  struct sgx_enclave_add_pages {
> -	__u64	src;
> -	__u64	offset;
> -	__u64	length;
> -	__u64	secinfo;
> -	__u64	flags;
> +	__u64 src;
> +	__u64 offset;
> +	__u64 length;
> +	__u64 secinfo;
> +	__u64 flags;
> +	__u64 count;
>  };
> /**
> diff --git a/arch/x86/kernel/cpu/sgx/ioctl.c  
> b/arch/x86/kernel/cpu/sgx/ioctl.c
> index 30de66f4247b..d10179b47daa 100644
> --- a/arch/x86/kernel/cpu/sgx/ioctl.c
> +++ b/arch/x86/kernel/cpu/sgx/ioctl.c
> @@ -449,16 +449,6 @@ static int sgx_encl_add_page(struct sgx_encl *encl,  
> unsigned long src,
>  	sgx_free_epc_page(epc_page);
>  	kfree(encl_page);
> -	/*
> -	 * Destroy enclave on ENCLS failure as this means that EPC has been
> -	 * invalidated.
> -	 */
> -	if (ret == -EIO) {
> -		mutex_lock(&encl->lock);
> -		sgx_encl_destroy(encl);
> -		mutex_unlock(&encl->lock);
> -	}
> -
>  	return ret;
>  }
> @@ -487,12 +477,15 @@ static int sgx_encl_add_page(struct sgx_encl  
> *encl, unsigned long src,
>   *
>   * 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.
> + * caller. In this situation the function destroys the enclave as it  
> cannot
> + * be recovered.
>   *
>   * 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
> + *   -ENOMEM if the system is out of EPC pages,
> + *   -EINTR if the call was interrupted before any data was processed,
> + *   -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)
> @@ -549,10 +542,16 @@ static long sgx_ioc_enclave_add_pages(struct  
> sgx_encl *encl, void __user *arg)
>  			break;
>  	}
> -	if (ret)
> -		return ret;
> +	addp.count = c;
> +
> +	/* On EADD or EEXTEND failure, destroy the enclave. */
> +	if (ret == -EIO) {
> +		mutex_lock(&encl->lock);
> +		sgx_encl_destroy(encl);
> +		mutex_unlock(&encl->lock);
> +	}
> -	return c;

missing copy_to_user for addp.count?

> +	return ret;
>  }
> static int __sgx_get_key_hash(struct crypto_shash *tfm, const void  
> *modulus,