Re: [PATCH V4 00/31] x86/sgx and selftests/sgx: Support SGX2

[Jarkko Sakkinen <jarkko@kernel.org>]

On Thu, Apr 21, 2022 at 08:29:31PM -0700, Reinette Chatre wrote:
> Hi Vijay and Mark,
> 
> On 4/21/2022 4:46 PM, Dhanraj, Vijay wrote:
> > Hi All,
> > 
> > I evaluated V4 patch changes with Gramine and ran into an issue when trying to set EPC page permission to PROT_NONE. It looks like with V3 patch series a change was introduced which requires kernel to have at least R permission when calling RESTRICT IOCTL. This change was done under the assumption that EPCM requires at least R permission for EMODPE/EACCEPT to succeed. But when testing with V2 version, EACCEPT worked fine with page permission set to PROT_NONE. 
> > 
> > Thanks to @Shanahan, Mark for confirming that EPCM does not need to have R value to allow EACCEPT or EMODPE. Given this, can we please revert this change?
> > 
> 
> Thank you very much for pointing this out. I can revert the change
> to what was done in V2 where the only check is to ensure that W requires R.
> This is a requirement of EMODPR. Could you please check if this snippet
> results in things working for you again?
> 
> ---8<---
> diff --git a/arch/x86/kernel/cpu/sgx/ioctl.c b/arch/x86/kernel/cpu/sgx/ioctl.c
> index 83674d054c13..7c7c8a61196e 100644
> --- a/arch/x86/kernel/cpu/sgx/ioctl.c
> +++ b/arch/x86/kernel/cpu/sgx/ioctl.c
> @@ -855,12 +855,8 @@ static long sgx_ioc_enclave_restrict_permissions(struct sgx_encl *encl,
>  	if (params.permissions & ~SGX_SECINFO_PERMISSION_MASK)
>  		return -EINVAL;
>  
> -	/*
> -	 * Read access is required for the enclave to be able to use the page.
> -	 * SGX instructions like ENCLU[EMODPE] and ENCLU[EACCEPT] require
> -	 * read access.
> -	 */
> -	if (!(params.permissions & SGX_SECINFO_R))
> +	if ((params.permissions & SGX_SECINFO_W) &&
> +	    !(params.permissions & SGX_SECINFO_R))
>  		return -EINVAL;
>  
>  	if (params.result || params.count)

Just adding that it's fine for me to revert this.

BR, Jarkko