From: "Xing, Cedric" <cedric.xing@intel.com>
To: "Christopherson, Sean J" <sean.j.christopherson@intel.com>,
"Jarkko Sakkinen" <jarkko.sakkinen@linux.intel.com>
Cc: Andy Lutomirski <luto@kernel.org>,
Stephen Smalley <sds@tycho.nsa.gov>,
James Morris <jmorris@namei.org>,
"Serge E . Hallyn" <serge@hallyn.com>,
LSM List <linux-security-module@vger.kernel.org>,
Paul Moore <paul@paul-moore.com>,
Eric Paris <eparis@parisplace.org>,
"selinux@vger.kernel.org" <selinux@vger.kernel.org>,
Jethro Beekman <jethro@fortanix.com>,
"Hansen, Dave" <dave.hansen@intel.com>,
"Thomas Gleixner" <tglx@linutronix.de>,
Linus Torvalds <torvalds@linux-foundation.org>,
LKML <linux-kernel@vger.kernel.org>, X86 ML <x86@kernel.org>,
"linux-sgx@vger.kernel.org" <linux-sgx@vger.kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
"nhorman@redhat.com" <nhorman@redhat.com>,
"npmccallum@redhat.com" <npmccallum@redhat.com>,
"Ayoun, Serge" <serge.ayoun@intel.com>,
"Katz-zamir, Shay" <shay.katz-zamir@intel.com>,
"Huang, Haitao" <haitao.huang@intel.com>,
"Andy Shevchenko" <andriy.shevchenko@linux.intel.com>,
"Svahn, Kai" <kai.svahn@intel.com>,
Borislav Petkov <bp@alien8.de>,
Josh Triplett <josh@joshtriplett.org>,
"Huang, Kai" <kai.huang@intel.com>,
David Rientjes <rientjes@google.com>,
"Roberts, William C" <william.c.roberts@intel.com>,
"Tricca, Philip B" <philip.b.tricca@intel.com>
Subject: RE: [RFC PATCH v2 2/5] x86/sgx: Require userspace to define enclave pages' protection bits
Date: Mon, 10 Jun 2019 18:29:34 +0000 [thread overview]
Message-ID: <960B34DE67B9E140824F1DCDEC400C0F65500E13@ORSMSX116.amr.corp.intel.com> (raw)
In-Reply-To: <20190606021145.12604-3-sean.j.christopherson@intel.com>
> From: Christopherson, Sean J
> Sent: Wednesday, June 05, 2019 7:12 PM
>
> +/**
> + * sgx_map_allowed - check vma protections against the associated
> enclave page
> + * @encl: an enclave
> + * @start: start address of the mapping (inclusive)
> + * @end: end address of the mapping (exclusive)
> + * @prot: protection bits of the mapping
> + *
> + * Verify a userspace mapping to an enclave page would not violate the
> +security
> + * requirements of the *kernel*. Note, this is in no way related to
> +the
> + * page protections enforced by hardware via the EPCM. The EPCM
> +protections
> + * can be directly extended by the enclave, i.e. cannot be relied upon
> +by the
> + * kernel for security guarantees of any kind.
> + *
> + * Return:
> + * 0 on success,
> + * -EACCES if the mapping is disallowed
> + */
> +int sgx_map_allowed(struct sgx_encl *encl, unsigned long start,
> + unsigned long end, unsigned long prot) {
> + struct sgx_encl_page *page;
> + unsigned long addr;
> +
> + prot &= (VM_READ | VM_WRITE | VM_EXEC);
> + if (!prot || !encl)
> + return 0;
> +
> + mutex_lock(&encl->lock);
> +
> + for (addr = start; addr < end; addr += PAGE_SIZE) {
> + page = radix_tree_lookup(&encl->page_tree, addr >>
> PAGE_SHIFT);
> +
> + /*
> + * Do not allow R|W|X to a non-existent page, or protections
> + * beyond those of the existing enclave page.
> + */
> + if (!page || (prot & ~page->prot))
> + return -EACCES;
In SGX2, pages will be "mapped" before being populated.
Here's a brief summary for those who don't have enough background on how new EPC pages could be added to a running enclave in SGX2:
- There are 2 new instructions - EACCEPT and EAUG.
- EAUG is used by SGX module to add (augment) a new page to an existing enclave. The newly added page is *inaccessible* until the enclave *accepts* it.
- EACCEPT is the instruction for an enclave to accept a new page.
And the s/w flow for an enclave to request new EPC pages is expected to be something like the following:
- The enclave issues EACCEPT at the linear address that it would like a new page.
- EACCEPT results in #PF, as there's no page at the linear address above.
- SGX module is notified about the #PF, in form of its vma->vm_ops->fault() being called by kernel.
- SGX module EAUGs a new EPC page at the fault address, and resumes the enclave.
- EACCEPT is reattempted, and succeeds at this time.
But with the above check in sgx_map_allowed(), I'm not sure how this will work out with SGX2.
> + }
> +
> + mutex_unlock(&encl->lock);
> +
> + return 0;
> +}
> +
next prev parent reply other threads:[~2019-06-10 18:29 UTC|newest]
Thread overview: 67+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-06 2:11 [RFC PATCH v2 0/5] security: x86/sgx: SGX vs. LSM Sean Christopherson
2019-06-06 2:11 ` [RFC PATCH v2 1/5] mm: Introduce vm_ops->may_mprotect() Sean Christopherson
2019-06-10 15:06 ` Jarkko Sakkinen
2019-06-10 15:55 ` Sean Christopherson
2019-06-10 17:47 ` Xing, Cedric
2019-06-10 19:49 ` Sean Christopherson
2019-06-10 22:06 ` Xing, Cedric
2019-06-06 2:11 ` [RFC PATCH v2 2/5] x86/sgx: Require userspace to define enclave pages' protection bits Sean Christopherson
2019-06-10 15:27 ` Jarkko Sakkinen
2019-06-10 16:15 ` Sean Christopherson
2019-06-10 17:45 ` Jarkko Sakkinen
2019-06-10 18:17 ` Sean Christopherson
2019-06-12 19:26 ` Jarkko Sakkinen
2019-06-10 18:29 ` Xing, Cedric [this message]
2019-06-10 19:15 ` Andy Lutomirski
2019-06-10 22:28 ` Xing, Cedric
2019-06-12 0:09 ` Andy Lutomirski
2019-06-12 14:34 ` Sean Christopherson
2019-06-12 18:20 ` Xing, Cedric
2019-06-06 2:11 ` [RFC PATCH v2 3/5] x86/sgx: Enforce noexec filesystem restriction for enclaves Sean Christopherson
2019-06-10 16:00 ` Jarkko Sakkinen
2019-06-10 16:44 ` Andy Lutomirski
2019-06-11 17:21 ` Stephen Smalley
2019-06-06 2:11 ` [RFC PATCH v2 4/5] LSM: x86/sgx: Introduce ->enclave_load() hook for Intel SGX Sean Christopherson
2019-06-07 19:58 ` Stephen Smalley
2019-06-10 16:21 ` Sean Christopherson
2019-06-10 16:05 ` Jarkko Sakkinen
2019-06-06 2:11 ` [RFC PATCH v2 5/5] security/selinux: Add enclave_load() implementation Sean Christopherson
2019-06-07 21:16 ` Stephen Smalley
2019-06-10 16:46 ` Sean Christopherson
2019-06-17 16:38 ` Jarkko Sakkinen
2019-06-10 7:03 ` [RFC PATCH v1 0/3] security/x86/sgx: SGX specific LSM hooks Cedric Xing
2019-06-10 7:03 ` [RFC PATCH v1 1/3] LSM/x86/sgx: Add " Cedric Xing
2019-06-10 7:03 ` [RFC PATCH v1 2/3] LSM/x86/sgx: Implement SGX specific hooks in SELinux Cedric Xing
2019-06-11 13:40 ` Stephen Smalley
2019-06-11 22:02 ` Sean Christopherson
2019-06-12 9:32 ` Dr. Greg
2019-06-12 14:25 ` Sean Christopherson
2019-06-13 7:25 ` Dr. Greg
2019-06-12 19:30 ` Andy Lutomirski
2019-06-12 22:02 ` Sean Christopherson
2019-06-13 0:10 ` Xing, Cedric
2019-06-13 1:02 ` Xing, Cedric
2019-06-13 17:02 ` Stephen Smalley
2019-06-13 23:03 ` Xing, Cedric
2019-06-13 23:17 ` Sean Christopherson
2019-06-14 0:31 ` Xing, Cedric
2019-06-14 0:46 ` Sean Christopherson
2019-06-14 15:38 ` Sean Christopherson
2019-06-16 22:14 ` Andy Lutomirski
2019-06-17 16:49 ` Sean Christopherson
2019-06-17 17:08 ` Andy Lutomirski
2019-06-18 15:40 ` Dr. Greg
2019-06-14 17:16 ` Xing, Cedric
2019-06-14 17:45 ` Sean Christopherson
2019-06-14 17:53 ` Sean Christopherson
2019-06-14 20:01 ` Sean Christopherson
2019-06-16 22:16 ` Andy Lutomirski
2019-06-14 23:19 ` Dr. Greg
2019-06-11 22:55 ` Xing, Cedric
2019-06-13 18:00 ` Stephen Smalley
2019-06-13 19:48 ` Sean Christopherson
2019-06-13 21:09 ` Xing, Cedric
2019-06-13 21:02 ` Xing, Cedric
2019-06-14 0:37 ` Sean Christopherson
2019-06-10 7:03 ` [RFC PATCH v1 3/3] LSM/x86/sgx: Call new LSM hooks from SGX subsystem Cedric Xing
2019-06-10 17:36 ` [RFC PATCH v1 0/3] security/x86/sgx: SGX specific LSM hooks Jarkko Sakkinen
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