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From: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
To: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: Andy Lutomirski <luto@kernel.org>, X86 ML <x86@kernel.org>,
	linux-sgx@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>,
	Linux-MM <linux-mm@kvack.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Matthew Wilcox <willy@infradead.org>,
	Jethro Beekman <jethro@fortanix.com>,
	Darren Kenny <darren.kenny@oracle.com>,
	Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
	asapek@google.com, Borislav Petkov <bp@alien8.de>,
	"Xing, Cedric" <cedric.xing@intel.com>,
	chenalexchen@google.com, Conrad Parker <conradparker@google.com>,
	cyhanish@google.com, Dave Hansen <dave.hansen@intel.com>,
	"Huang, Haitao" <haitao.huang@intel.com>,
	Josh Triplett <josh@joshtriplett.org>,
	"Huang, Kai" <kai.huang@intel.com>,
	"Svahn, Kai" <kai.svahn@intel.com>, Keith Moyer <kmoy@google.com>,
	Christian Ludloff <ludloff@google.com>,
	Neil Horman <nhorman@redhat.com>,
	Nathaniel McCallum <npmccallum@redhat.com>,
	Patrick Uiterwijk <puiterwijk@redhat.com>,
	David Rientjes <rientjes@google.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	yaozhangx@google.com
Subject: Re: [PATCH v38 10/24] mm: Add vm_ops->mprotect()
Date: Tue, 22 Sep 2020 08:29:57 +0300	[thread overview]
Message-ID: <20200922052957.GA97272@linux.intel.com> (raw)
In-Reply-To: <20200921211849.GA25403@linux.intel.com>

On Mon, Sep 21, 2020 at 02:18:49PM -0700, Sean Christopherson wrote:
> On Tue, Sep 22, 2020 at 12:07:36AM +0300, Jarkko Sakkinen wrote:
> > On Mon, Sep 21, 2020 at 09:57:58AM -0700, Sean Christopherson wrote:
> > > On Mon, Sep 21, 2020 at 03:49:46PM +0300, Jarkko Sakkinen wrote:
> > > > On Fri, Sep 18, 2020 at 04:53:37PM -0700, Sean Christopherson wrote:
> > > > > a noexec filesystem by loading code into an enclave, and to give the kernel the
> > > > > option of adding enclave specific LSM policies in the future.
> > > > > 
> > > > > The source file (if one exists) for the enclave is long gone when the enclave
> > > > > is actually mmap()'d and mprotect()'d.  To enforce noexec, the requested
> > > > > permissions for a given page are snapshotted when the page is added to the
> > > > > enclave, i.e. when the enclave is built.  Enclave pages that will be executable
> > > > > must originate from an a MAYEXEC VMA, e.g. the source page can't come from a
> > > > > noexec file system.
> > > > 
> > > > noexec check is done in __sgx_encl_add_page(), not in this callback.
> > > > sgx_vma_mprotect() calls sgx_encl_may_map(), which iterates the
> > > > addresses, checks that permissions are not surpassed and there are
> > > > no holes.
> > > 
> > > Yes, that's what I said.
> > 
> > sgx_encl_add_page() will remove such page. The callback does not
> > interact with this process as such pages never get to the enclave.
> 
> I think we're in violent agreement, mostly.
> 
> Userspace can add the page without EXEC permissions in the EPCM, and thus
> avoid the noexec/VM_MAYEXEC check.  The enclave can then do EMODPE to gain
> EXEC permissions in the EPMC.  Without the ->mprotect() hook, we wouldn't
> be able to detect/prevent such shenanigans.

Right, the VM_MAYEXEC in the code is nested under VM_EXEC check.

I'm only wondering why not block noexec completely with any permissions,
i.e. why not just have unconditional VM_MAYEXEC check?

/Jarkko


  reply	other threads:[~2020-09-22  5:30 UTC|newest]

Thread overview: 81+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20200915112842.897265-1-jarkko.sakkinen@linux.intel.com>
2020-09-15 11:28 ` [PATCH v38 10/24] mm: Add vm_ops->mprotect() Jarkko Sakkinen
2020-09-18 12:44   ` Borislav Petkov
2020-09-18 15:09   ` Andy Lutomirski
2020-09-18 23:24     ` [PATCH v38 10/24] mm: Add vm_ops->mprotect()' Jarkko Sakkinen
2020-09-18 23:53     ` [PATCH v38 10/24] mm: Add vm_ops->mprotect() Sean Christopherson
2020-09-19  0:15       ` Andy Lutomirski
2020-09-22 12:58         ` Jarkko Sakkinen
2020-09-22 15:11           ` Dave Hansen
2020-09-23 13:30             ` Jarkko Sakkinen
2020-09-23 13:43             ` Jarkko Sakkinen
2020-09-23 14:33             ` Jarkko Sakkinen
2020-09-24 14:50               ` Dave Hansen
2020-09-24 16:27                 ` Sean Christopherson
2020-09-24 19:35                 ` Jarkko Sakkinen
2020-09-21 12:49       ` Jarkko Sakkinen
2020-09-21 12:51         ` Jarkko Sakkinen
2020-09-21 13:14         ` Jarkko Sakkinen
2020-09-21 16:57         ` Sean Christopherson
2020-09-21 21:07           ` Jarkko Sakkinen
2020-09-21 21:18             ` Sean Christopherson
2020-09-22  5:29               ` Jarkko Sakkinen [this message]
2020-09-22  5:35                 ` Jarkko Sakkinen
2020-09-22 16:43                   ` Sean Christopherson
2020-09-23 13:50                     ` Jarkko Sakkinen
2020-09-24 19:11                       ` Haitao Huang
2020-09-24 19:28                         ` Sean Christopherson
2020-09-24 19:39                           ` Dave Hansen
2020-09-24 20:01                             ` Sean Christopherson
2020-09-24 20:10                               ` Dave Hansen
2020-09-24 20:25                                 ` Sean Christopherson
2020-09-24 20:54                                   ` Dave Hansen
2020-09-24 22:10                                     ` Jarkko Sakkinen
2020-09-24 23:05                                     ` Sean Christopherson
2020-09-24 23:09                                       ` Dave Hansen
2020-09-25  0:00                                         ` Sean Christopherson
2020-09-25 17:18                                           ` Dave Hansen
2020-09-25 19:43                                             ` Sean Christopherson
2020-09-25 19:53                                               ` Dave Hansen
2020-09-26  4:15                                                 ` Andy Lutomirski
2020-09-28  0:53                                                 ` Jarkko Sakkinen
2020-09-28 14:04                                                   ` Dave Hansen
2020-09-28 16:19                                                     ` Jarkko Sakkinen
2020-09-28 16:48                                                       ` Dave Hansen
2020-09-28 19:32                                                         ` Jarkko Sakkinen
2020-09-28 19:45                                                           ` Dave Hansen
2020-09-28 20:19                                                             ` Jarkko Sakkinen
2020-09-29  1:37                                                               ` Andy Lutomirski
2020-09-29  4:05                                                                 ` Jarkko Sakkinen
2020-09-29 14:24                                                                   ` Dave Hansen
2020-09-30  0:20                                                                     ` Jarkko Sakkinen
2020-09-30 14:35                                                                       ` Dave Hansen
2020-09-28 20:18                                                         ` Jarkko Sakkinen
2020-10-18  8:49                                                     ` Dr. Greg
2020-10-19 21:31                                                       ` Sean Christopherson
2020-10-20 10:01                                                         ` Dr. Greg
2020-10-20 16:40                                                           ` Sean Christopherson
2020-10-24 14:37                                                             ` Dr. Greg
2020-10-24 15:33                                                               ` Andy Lutomirski
2020-10-26 10:51                                                                 ` Dr. Greg
2020-10-26 22:59                                                                   ` Andy Lutomirski
2020-10-27  0:40                                                                     ` Sean Christopherson
2020-09-24 22:07                                 ` Jarkko Sakkinen
2020-09-24 21:58                           ` Jarkko Sakkinen
2020-09-24 21:55                         ` Jarkko Sakkinen
2020-09-15 11:28 ` [PATCH v38 11/24] x86/sgx: Add SGX enclave driver Jarkko Sakkinen
2020-09-21  9:30   ` Borislav Petkov
2020-09-21 12:09     ` Jarkko Sakkinen
2020-10-01 17:36   ` Sean Christopherson
2020-10-01 18:49     ` Jarkko Sakkinen
2020-09-15 11:28 ` [PATCH v38 16/24] x86/sgx: Add a page reclaimer Jarkko Sakkinen
2020-09-22 10:45   ` Borislav Petkov
2020-09-22 14:03     ` Jarkko Sakkinen
2020-09-22 14:24       ` Borislav Petkov
2020-09-23 14:52         ` Jarkko Sakkinen
2020-09-29  1:14       ` Sean Christopherson
2020-09-29  3:50         ` Jarkko Sakkinen
2020-09-29  8:35           ` Sean Christopherson
2020-09-22 16:24     ` Sean Christopherson
2020-09-22 18:02       ` Borislav Petkov
2020-09-23 15:25       ` Jarkko Sakkinen
     [not found] <20200915110522.893152-1-jarkko.sakkinen@linux.intel.com>
2020-09-15 11:05 ` [PATCH v38 10/24] mm: Add vm_ops->mprotect() Jarkko Sakkinen

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