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From: Sean Christopherson <sean.j.christopherson@intel.com>
To: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Cc: Haitao Huang <haitao.huang@linux.intel.com>,
	x86@kernel.org, linux-sgx@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	Jethro Beekman <jethro@fortanix.com>,
	Chunyang Hui <sanqian.hcy@antfin.com>,
	Jordan Hand <jorhand@linux.microsoft.com>,
	Nathaniel McCallum <npmccallum@redhat.com>,
	Seth Moore <sethmo@google.com>,
	Darren Kenny <darren.kenny@oracle.com>,
	Suresh Siddha <suresh.b.siddha@intel.com>,
	akpm@linux-foundation.org, andriy.shevchenko@linux.intel.com,
	asapek@google.com, bp@alien8.de, cedric.xing@intel.com,
	chenalexchen@google.com, conradparker@google.com,
	cyhanish@google.com, dave.hansen@intel.com,
	haitao.huang@intel.com, josh@joshtriplett.org,
	kai.huang@intel.com, kai.svahn@intel.com, kmoy@google.com,
	ludloff@google.com, luto@kernel.org, nhorman@redhat.com,
	puiterwijk@redhat.com, rientjes@google.com, tglx@linutronix.de,
	yaozhangx@google.com
Subject: Re: [PATCH v38 13/24] x86/sgx: Add SGX_IOC_ENCLAVE_ADD_PAGES
Date: Mon, 21 Sep 2020 12:57:39 -0700	[thread overview]
Message-ID: <20200921195738.GB25005@linux.intel.com> (raw)
In-Reply-To: <20200921194419.GA56547@linux.intel.com>

On Mon, Sep 21, 2020 at 10:44:19PM +0300, Jarkko Sakkinen wrote:
> On Mon, Sep 21, 2020 at 09:49:48PM +0300, Jarkko Sakkinen wrote:
> > To have understandable semantics you have to map error codes to
> > conditions rather than opcodes. -EIO means loss of enclave in the event
> > of EPC gone invalid. Enclave is already lost, that is the reason why we
> > deinitialize the kernel data structures.
> > 
> > EADD must have a different error code because nothing is actually lost
> > but the failure conditions are triggered outside. -EFAULT would be
> > probably the most reasonable choice for that.
> 
> Now that I did all the changes discussed and then I remember why EADD
> and EEXTEND had a common error code, and common behaviour. Obviously EADD
> can also fail because of EPC reset because it depends on a valid SECS
> page.
> 
> If we cannot distinct from EADD caused by EPC loss and EADD caused by
> problems with the source, it should have the same error code, and also
> the enclave should be deinitialized, whenver this happens.

Hmm, on SGX2 hardware the kernel can precisely and accurately identify loss
of EPC, or at least "problem with the EPCM", as such a condition will be a
page fault with PFEC.SGX=1.

But getting that info back to the ENCLS invocation would require adding a
new exception fixup handler in order to "return" the error code.  Given that
this is the only case where that level of precision makes a difference, I
think it's ok to just kill the enclave on any EADD failure.  Practically
speaking I highly doubt the overzealous killing will impact userspace, I
would imagine any SGX runtime would treat -EFAULT as fatal anyways.

Side topic, this does invalidate my argument for not killing the enclave on
EADD failure.  If EADD fails due to loss of EPC, it's theoretically possible
userspace could get stuck in an infinite loop if it does a naive retry on
-EIO or whatever.

> So I would just revert to v38 behaviour, keeping of course the whole
> check more visible in sgx_ioc_enclave_add_pages(), and just refine
> the documentation better describe the whole situation.
> 
> /Jarkko

  reply	other threads:[~2020-09-21 19:57 UTC|newest]

Thread overview: 41+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-15 11:04 [PATCH v38 00/24] Intel SGX foundations Jarkko Sakkinen
2020-09-15 11:04 ` [PATCH v38 01/24] x86/cpufeatures: x86/msr: Add Intel SGX hardware bits Jarkko Sakkinen
2020-09-15 11:05 ` [PATCH v38 02/24] x86/cpufeatures: x86/msr: Add Intel SGX Launch Control " Jarkko Sakkinen
2020-09-15 11:05 ` [PATCH v38 03/24] x86/mm: x86/sgx: Signal SIGSEGV with PF_SGX Jarkko Sakkinen
2020-09-15 11:05 ` [PATCH v38 04/24] x86/sgx: Add SGX microarchitectural data structures Jarkko Sakkinen
2020-09-15 11:05 ` [PATCH v38 05/24] x86/sgx: Add wrappers for ENCLS leaf functions Jarkko Sakkinen
2020-09-15 11:05 ` [PATCH v38 06/24] x86/cpu/intel: Detect SGX support Jarkko Sakkinen
2020-09-15 11:05 ` [PATCH v38 07/24] x86/cpu/intel: Add nosgx kernel parameter Jarkko Sakkinen
2020-09-15 11:05 ` [PATCH v38 08/24] x86/sgx: Initialize metadata for Enclave Page Cache (EPC) sections Jarkko Sakkinen
2020-09-15 11:05 ` [PATCH v38 09/24] x86/sgx: Add __sgx_alloc_epc_page() and sgx_free_epc_page() Jarkko Sakkinen
2020-09-15 11:05 ` [PATCH v38 10/24] mm: Add vm_ops->mprotect() Jarkko Sakkinen
2020-09-15 11:05 ` [PATCH v38 11/24] x86/sgx: Add SGX enclave driver Jarkko Sakkinen
2020-09-15 11:05 ` [PATCH v38 12/24] x86/sgx: Add SGX_IOC_ENCLAVE_CREATE Jarkko Sakkinen
2020-09-15 11:05 ` [PATCH v38 13/24] x86/sgx: Add SGX_IOC_ENCLAVE_ADD_PAGES Jarkko Sakkinen
     [not found]   ` <op.0q2prldowjvjmi@mqcpg7oapc828.gar.corp.intel.com>
2020-09-17 16:02     ` Jarkko Sakkinen
2020-09-17 18:35       ` Haitao Huang
2020-09-18  2:09         ` Sean Christopherson
2020-09-18 12:20           ` Jarkko Sakkinen
2020-09-18 12:39             ` Jarkko Sakkinen
     [not found]               ` <20200919000918.GB21189@sjchrist-ice>
2020-09-21 11:41                 ` Jarkko Sakkinen
2020-09-21 16:46                   ` Sean Christopherson
2020-09-21 18:49                     ` Jarkko Sakkinen
2020-09-21 19:44                       ` Jarkko Sakkinen
2020-09-21 19:57                         ` Sean Christopherson [this message]
2020-09-21 21:24                           ` Jarkko Sakkinen
2020-09-21 19:58                         ` Jarkko Sakkinen
2020-09-17 16:03     ` Jarkko Sakkinen
2020-09-15 11:05 ` [PATCH v38 14/24] x86/sgx: Add SGX_IOC_ENCLAVE_INIT Jarkko Sakkinen
2020-09-15 11:05 ` [PATCH v38 15/24] x86/sgx: Enable provisioning for remote attestation Jarkko Sakkinen
2020-10-01 17:17   ` Sean Christopherson
2020-09-15 11:05 ` [PATCH v38 16/24] x86/sgx: Add a page reclaimer Jarkko Sakkinen
2020-09-15 11:05 ` [PATCH v38 17/24] x86/sgx: ptrace() support for the SGX driver Jarkko Sakkinen
2020-09-15 11:05 ` [PATCH v38 18/24] x86/vdso: Add support for exception fixup in vDSO functions Jarkko Sakkinen
2020-09-15 11:05 ` [PATCH v38 19/24] x86/fault: Add helper function to sanitize error code Jarkko Sakkinen
2020-09-15 11:05 ` [PATCH v38 20/24] x86/traps: Attempt to fixup exceptions in vDSO before signaling Jarkko Sakkinen
2020-09-15 11:05 ` [PATCH v38 21/24] x86/vdso: Implement a vDSO for Intel SGX enclave call Jarkko Sakkinen
2020-09-28  1:32   ` Jarkko Sakkinen
2020-09-15 11:05 ` [PATCH v38 22/24] selftests/x86: Add a selftest for SGX Jarkko Sakkinen
2020-09-15 11:05 ` [PATCH v38 23/24] docs: x86/sgx: Document SGX micro architecture and kernel internals Jarkko Sakkinen
2020-09-15 11:05 ` [PATCH v38 24/24] x86/sgx: Update MAINTAINERS Jarkko Sakkinen
2020-09-15 11:28 [PATCH v38 00/24] Intel SGX foundations Jarkko Sakkinen
2020-09-15 11:28 ` [PATCH v38 13/24] x86/sgx: Add SGX_IOC_ENCLAVE_ADD_PAGES Jarkko Sakkinen

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