From: Sean Christopherson <sean.j.christopherson@intel.com>
To: Stephen Smalley <sds@tycho.nsa.gov>
Cc: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>,
Andy Lutomirski <luto@kernel.org>,
Cedric Xing <cedric.xing@intel.com>,
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, Jethro Beekman <jethro@fortanix.com>,
Dave Hansen <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,
Andrew Morton <akpm@linux-foundation.org>,
nhorman@redhat.com, npmccallum@redhat.com,
Serge Ayoun <serge.ayoun@intel.com>,
Shay Katz-zamir <shay.katz-zamir@intel.com>,
Haitao Huang <haitao.huang@intel.com>,
Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
Kai Svahn <kai.svahn@intel.com>, Borislav Petkov <bp@alien8.de>,
Josh Triplett <josh@joshtriplett.org>,
Kai Huang <kai.huang@intel.com>,
David Rientjes <rientjes@google.com>,
William Roberts <william.c.roberts@intel.com>,
Philip Tricca <philip.b.tricca@intel.com>
Subject: Re: [RFC PATCH v2 4/5] LSM: x86/sgx: Introduce ->enclave_load() hook for Intel SGX
Date: Mon, 10 Jun 2019 09:21:51 -0700 [thread overview]
Message-ID: <20190610162150.GD15995@linux.intel.com> (raw)
In-Reply-To: <5706a7ec-5497-c560-92fa-91c9751b9096@tycho.nsa.gov>
On Fri, Jun 07, 2019 at 03:58:34PM -0400, Stephen Smalley wrote:
> On 6/5/19 10:11 PM, Sean Christopherson wrote:
> >enclave_load() is roughly analogous to the existing file_mprotect().
> >
> >Due to the nature of SGX and its Enclave Page Cache (EPC), all enclave
> >VMAs are backed by a single file, i.e. /dev/sgx/enclave, that must be
> >MAP_SHARED. Furthermore, all enclaves need read, write and execute
> >VMAs. As a result, the existing/standard call to file_mprotect() does
> >not provide any meaningful security for enclaves since an LSM can only
> >deny/grant access to the EPC as a whole.
> >
> >security_enclave_load() is called when SGX is first loading an enclave
> >page, i.e. copying a page from normal memory into the EPC. Although
> >the prototype for enclave_load() is similar to file_mprotect(), e.g.
> >SGX could theoretically use file_mprotect() and set reqprot=prot, a
> >separate hook is desirable as the semantics of an enclave's protection
> >bits are different than those of vmas, e.g. an enclave page tracks the
> >maximal set of protections, whereas file_mprotect() operates on the
> >actual protections being provided. In other words, LSMs will likely
> >want to implement different policies for enclave page protections.
> >
> >Note, extensive discussion yielded no sane alternative to some form of
> >SGX specific LSM hook[1].
> >
> >[1] https://lkml.kernel.org/r/CALCETrXf8mSK45h7sTK5Wf+pXLVn=Bjsc_RLpgO-h-qdzBRo5Q@mail.gmail.com
> >
> >Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
> >---
> > arch/x86/kernel/cpu/sgx/driver/ioctl.c | 12 ++++++------
> > include/linux/lsm_hooks.h | 13 +++++++++++++
> > include/linux/security.h | 12 ++++++++++++
> > security/security.c | 7 +++++++
> > 4 files changed, 38 insertions(+), 6 deletions(-)
> >
> >diff --git a/arch/x86/kernel/cpu/sgx/driver/ioctl.c b/arch/x86/kernel/cpu/sgx/driver/ioctl.c
> >index 44b2d73de7c3..29c0df672250 100644
> >--- a/arch/x86/kernel/cpu/sgx/driver/ioctl.c
> >+++ b/arch/x86/kernel/cpu/sgx/driver/ioctl.c
> >@@ -8,6 +8,7 @@
> > #include <linux/highmem.h>
> > #include <linux/ratelimit.h>
> > #include <linux/sched/signal.h>
> >+#include <linux/security.h>
> > #include <linux/shmem_fs.h>
> > #include <linux/slab.h>
> > #include <linux/suspend.h>
> >@@ -582,9 +583,6 @@ static int sgx_encl_page_copy(void *dst, unsigned long src, unsigned long prot)
> > struct vm_area_struct *vma;
> > int ret;
> >- if (!(prot & VM_EXEC))
> >- return 0;
> >-
>
> Is there a real use case where LSM will want to be called if !(prot &
> VM_EXEC)?
I don't think so? I have no objection to conditioning the LSM calls on
the page being executable. I actually had the code written that way in
the first RFC, but it felt weird for SGX to be making assumptions about
LSM use cases.
> Also, you seem to be mixing prot and PROT_EXEC with vm_flags and
> VM_EXEC; other code does not appear to assume they are identical and
> explicitly converts, e.g. calc_vm_prot_bits().
Argh, I'll clean that up.
> > /* Hold mmap_sem across copy_from_user() to avoid a TOCTOU race. */
> > down_read(¤t->mm->mmap_sem);
next prev parent reply other threads:[~2019-06-10 16:21 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
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 [this message]
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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