linux-kernel - RE: [PATCH V4 00/31] x86/sgx and selftests/sgx: Support SGX2

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Date:   Mon, 25 Apr 2022 20:17:05 +0000
From:   "Dhanraj, Vijay" <vijay.dhanraj@...el.com>
To:     Jarkko Sakkinen <jarkko@...nel.org>,
        "Chatre, Reinette" <reinette.chatre@...el.com>
CC:     "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "bp@...en8.de" <bp@...en8.de>,
        "Lutomirski, Andy" <luto@...nel.org>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "linux-sgx@...r.kernel.org" <linux-sgx@...r.kernel.org>,
        "x86@...nel.org" <x86@...nel.org>,
        "shuah@...nel.org" <shuah@...nel.org>,
        "linux-kselftest@...r.kernel.org" <linux-kselftest@...r.kernel.org>,
        "Shanahan, Mark" <mark.shanahan@...el.com>,
        "Christopherson,, Sean" <seanjc@...gle.com>,
        "Huang, Kai" <kai.huang@...el.com>,
        "Zhang, Cathy" <cathy.zhang@...el.com>,
        "Xing, Cedric" <cedric.xing@...el.com>,
        "Huang, Haitao" <haitao.huang@...el.com>,
        "hpa@...or.com" <hpa@...or.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH V4 00/31] x86/sgx and selftests/sgx: Support SGX2

Hi Reinette and Jarkko,

> 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.

Thanks, I verified your patch and now I am able to set EPCM page permission with PROT_NONE.

I also verified the following SGX2 interfaces,
SGX_IOC_ENCLAVE_MODIFY_TYPES
SGX_IOC_ENCLAVE_REMOVE_PAGES
SGX_IOC_ENCLAVE_RESTRICT_PERMISSIONS

And also tested dynamically adding pages to enclave using #PF based approach and this works as expected.

Please feel free to add my Tested-by for the below patches which test the above IOCTLs

[PATCH V4 16/31] x86/sgx: Support adding of pages to an initialized enclave
[PATCH V4 15/31] x86/sgx: Support restricting of enclave page permissions
[PATCH V4 18/31] x86/sgx: Support modifying SGX page type
[PATCH V4 19/31] x86/sgx: Support complete page removal

> 
> BR, Jarkko