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

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Message-ID: <a94e4098-f5c1-f9ff-fab0-c2e5210cf188@intel.com>
Date:   Thu, 21 Apr 2022 20:29:31 -0700
From:   Reinette Chatre <reinette.chatre@...el.com>
To:     "Dhanraj, Vijay" <vijay.dhanraj@...el.com>,
        Jarkko Sakkinen <jarkko@...nel.org>,
        "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>
CC:     "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 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)
-- 


Thank you very much

Reinette