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From: Sean Christopherson <sean.j.christopherson@intel.com>
To: "Xing, Cedric" <cedric.xing@intel.com>
Cc: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>,
	Andy Lutomirski <luto@amacapital.net>,
	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 2/9] x86/sgx: Do not naturally align MAP_FIXED address
Date: Thu, 13 Jun 2019 10:14:51 -0700
Message-ID: <20190613171451.GD5850@linux.intel.com> (raw)
In-Reply-To: <960B34DE67B9E140824F1DCDEC400C0F65503A93@ORSMSX116.amr.corp.intel.com>

On Thu, Jun 13, 2019 at 09:47:06AM -0700, Xing, Cedric wrote:
> > From: Jarkko Sakkinen [mailto:jarkko.sakkinen@linux.intel.com]
> > Sent: Thursday, June 13, 2019 6:48 AM
> > 
> > On Thu, Jun 06, 2019 at 06:37:10PM +0300, Jarkko Sakkinen wrote:
> > > On Wed, Jun 05, 2019 at 01:14:04PM -0700, Andy Lutomirski wrote:
> > > >
> > > >
> > > > > On Jun 5, 2019, at 8:17 AM, Jarkko Sakkinen
> > <jarkko.sakkinen@linux.intel.com> wrote:
> > > > >
> > > > >> On Tue, Jun 04, 2019 at 10:10:22PM +0000, Xing, Cedric wrote:
> > > > >> A bit off topic here. This mmap()/mprotect() discussion reminds
> > > > >> me a question (guess for Jarkko): Now that
> > > > >> vma->vm_file->private_data keeps a pointer to the enclave, why do
> > we store it again in vma->vm_private?
> > > > >> It isn't a big deal but non-NULL vm_private does prevent
> > > > >> mprotect() from merging adjacent VMAs.
> > > > >
> > > > > Same semantics as with a regular mmap i.e. you can close the file
> > > > > and still use the mapping.
> > > > >
> > > > >
> > > >
> > > > The file should be properly refcounted — vm_file should not go away
> > while it’s mapped.
> > 
> > mm already takes care of that so vm_file does not go away. Still we need
> > an internal refcount for enclaves to synchronize with the swapper. In
> > summary nothing needs to be done.
> 
> I don't get this. The swapper takes a read lock on mm->mmap_sem, which locks
> the vma, which in turn reference counts vma->vm_file. Why is the internal
> refcount still needed? 

mmap_sem is only held when reclaim is touching PTEs, e.g. to test/clear
its accessed bit and to zap the PTE.  The liveliness of the enclave needs
to be guaranteed for the entire duration of reclaim, e.g. we can't have
the enclave disappearing when we go to do EWB.  It's also worth nothing
that a single reclaim may operate on more than one mmap_sem, as enclaves
can be shared across processes (mm_structs).

  reply index

Thread overview: 77+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-31 23:31 [RFC PATCH 0/9] security: x86/sgx: SGX vs. LSM Sean Christopherson
2019-05-31 23:31 ` [RFC PATCH 1/9] x86/sgx: Remove unused local variable in sgx_encl_release() Sean Christopherson
2019-06-04 11:41   ` Jarkko Sakkinen
2019-05-31 23:31 ` [RFC PATCH 2/9] x86/sgx: Do not naturally align MAP_FIXED address Sean Christopherson
2019-06-04 11:49   ` Jarkko Sakkinen
2019-06-04 20:16     ` Andy Lutomirski
2019-06-04 22:10       ` Xing, Cedric
2019-06-05 14:08         ` Sean Christopherson
2019-06-05 15:17         ` Jarkko Sakkinen
2019-06-05 20:14           ` Andy Lutomirski
2019-06-06 15:37             ` Jarkko Sakkinen
2019-06-13 13:48               ` Jarkko Sakkinen
2019-06-13 16:47                 ` Xing, Cedric
2019-06-13 17:14                   ` Sean Christopherson [this message]
2019-06-14 15:18                     ` Jarkko Sakkinen
2019-06-05 15:15       ` Jarkko Sakkinen
2019-05-31 23:31 ` [RFC PATCH 3/9] x86/sgx: Allow userspace to add multiple pages in single ioctl() Sean Christopherson
2019-06-03  6:26   ` Xing, Cedric
2019-06-03 20:08     ` Sean Christopherson
2019-06-03 20:39       ` Sean Christopherson
2019-06-03 23:45         ` Xing, Cedric
2019-06-04  0:54           ` Sean Christopherson
2019-06-04 20:18         ` Andy Lutomirski
2019-06-04 22:02           ` Xing, Cedric
2019-06-03 20:14   ` Dave Hansen
2019-06-03 20:37     ` Sean Christopherson
2019-06-03 20:39       ` Dave Hansen
2019-06-03 23:48       ` Xing, Cedric
2019-06-04  0:55         ` Sean Christopherson
2019-06-04 11:55   ` Jarkko Sakkinen
2019-05-31 23:31 ` [RFC PATCH 4/9] mm: Introduce vm_ops->mprotect() Sean Christopherson
2019-06-03  6:27   ` Xing, Cedric
2019-06-04 12:24   ` Jarkko Sakkinen
2019-06-04 14:51   ` Andy Lutomirski
2019-05-31 23:31 ` [RFC PATCH 5/9] x86/sgx: Restrict mapping without an enclave page to PROT_NONE Sean Christopherson
2019-06-03  6:28   ` Xing, Cedric
2019-06-04 15:32   ` Jarkko Sakkinen
2019-05-31 23:31 ` [RFC PATCH 6/9] x86/sgx: Require userspace to provide allowed prots to ADD_PAGES Sean Christopherson
2019-06-03  6:28   ` Xing, Cedric
2019-06-04 16:23   ` Jarkko Sakkinen
2019-06-04 16:45     ` Sean Christopherson
2019-06-05 15:06       ` Jarkko Sakkinen
2019-06-04 20:23   ` Andy Lutomirski
2019-06-05 11:10   ` Ayoun, Serge
2019-06-05 23:58     ` Sean Christopherson
2019-05-31 23:31 ` [RFC PATCH 7/9] x86/sgx: Enforce noexec filesystem restriction for enclaves Sean Christopherson
2019-06-03  6:29   ` Xing, Cedric
2019-06-04 20:26     ` Andy Lutomirski
2019-06-04 16:25   ` Jarkko Sakkinen
2019-06-04 20:25     ` Andy Lutomirski
2019-06-04 20:34       ` Sean Christopherson
2019-06-04 21:54       ` Xing, Cedric
2019-06-05 15:10       ` Jarkko Sakkinen
2019-06-06  1:01         ` Sean Christopherson
2019-05-31 23:31 ` [RFC PATCH 8/9] LSM: x86/sgx: Introduce ->enclave_load() hook for Intel SGX Sean Christopherson
2019-06-03  6:28   ` Xing, Cedric
2019-06-03 14:19   ` Stephen Smalley
2019-06-03 14:42     ` Sean Christopherson
2019-06-03 18:38       ` Stephen Smalley
2019-06-03 18:45         ` Dave Hansen
2019-06-04 20:29   ` Andy Lutomirski
2019-06-04 20:36     ` Sean Christopherson
2019-06-04 21:43       ` Xing, Cedric
2019-06-06  2:04         ` Sean Christopherson
2019-05-31 23:31 ` [RFC PATCH 9/9] security/selinux: Add enclave_load() implementation Sean Christopherson
2019-06-03 15:01   ` Stephen Smalley
2019-06-03 15:50     ` Sean Christopherson
2019-06-02  7:29 ` [RFC PATCH 0/9] security: x86/sgx: SGX vs. LSM Xing, Cedric
2019-06-03 17:15   ` Sean Christopherson
2019-06-03 18:30     ` Xing, Cedric
2019-06-04  1:36       ` Sean Christopherson
2019-06-04 15:33       ` Stephen Smalley
2019-06-04 16:30         ` Sean Christopherson
2019-06-04 21:38         ` Xing, Cedric
2019-06-03 17:47   ` Stephen Smalley
2019-06-03 18:02     ` Xing, Cedric
2019-06-04 11:15 ` Jarkko Sakkinen

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