Linux-Security-Module Archive on lore.kernel.org
 help / color / Atom feed
From: Sean Christopherson <sean.j.christopherson@intel.com>
To: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Cc: Andy Lutomirski <luto@kernel.org>,
	Cedric Xing <cedric.xing@intel.com>,
	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, 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: [RFC PATCH v2 1/5] mm: Introduce vm_ops->may_mprotect()
Date: Wed,  5 Jun 2019 19:11:41 -0700
Message-ID: <20190606021145.12604-2-sean.j.christopherson@intel.com> (raw)
In-Reply-To: <20190606021145.12604-1-sean.j.christopherson@intel.com>

SGX will use the may_mprotect() hook to prevent userspace from
circumventing various security checks, e.g. Linux Security Modules.
Naming it may_mprotect() instead of simply mprotect() is intended to
reflect the hook's purpose as a way to gate mprotect() as opposed to
a wholesale replacement.

Enclaves are built by copying data from normal memory into the Enclave
Page Cache (EPC).  Due to the nature of SGX, the EPC is represented by a
single file that must be MAP_SHARED, i.e. mprotect() only ever sees a
MAP_SHARED vm_file that references single file path.  Furthermore, all
enclaves will need read, write and execute pages in the EPC.

As a result, LSM policies cannot be meaningfully applied, e.g. an LSM
can deny access to the EPC as a whole, but can't deny PROT_EXEC on page
that originated in a non-EXECUTE file (which is long gone by the time
mprotect() is called).

By hooking mprotect(), SGX can make explicit LSM upcalls while an
enclave is being built, i.e. when the kernel has a handle to origin of
each enclave page, and enforce the result of the LSM policy whenever
userspace maps the enclave page in the future.

Alternatively, SGX could play games with MAY_{READ,WRITE,EXEC}, but
that approach is quite ugly, e.g. would require userspace to call an
SGX ioctl() prior to using mprotect() to extend a page's protections.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
---
 include/linux/mm.h |  2 ++
 mm/mprotect.c      | 15 +++++++++++----
 2 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 0e8834ac32b7..a697996040ac 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -458,6 +458,8 @@ struct vm_operations_struct {
 	void (*close)(struct vm_area_struct * area);
 	int (*split)(struct vm_area_struct * area, unsigned long addr);
 	int (*mremap)(struct vm_area_struct * area);
+	int (*may_mprotect)(struct vm_area_struct * area, unsigned long start,
+			    unsigned long end, unsigned long prot);
 	vm_fault_t (*fault)(struct vm_fault *vmf);
 	vm_fault_t (*huge_fault)(struct vm_fault *vmf,
 			enum page_entry_size pe_size);
diff --git a/mm/mprotect.c b/mm/mprotect.c
index bf38dfbbb4b4..18732543b295 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -547,13 +547,20 @@ static int do_mprotect_pkey(unsigned long start, size_t len,
 			goto out;
 		}
 
-		error = security_file_mprotect(vma, reqprot, prot);
-		if (error)
-			goto out;
-
 		tmp = vma->vm_end;
 		if (tmp > end)
 			tmp = end;
+
+		if (vma->vm_ops && vma->vm_ops->may_mprotect) {
+			error = vma->vm_ops->may_mprotect(vma, nstart, tmp, prot);
+			if (error)
+				goto out;
+		}
+
+		error = security_file_mprotect(vma, reqprot, prot);
+		if (error)
+			goto out;
+
 		error = mprotect_fixup(vma, &prev, nstart, tmp, newflags);
 		if (error)
 			goto out;
-- 
2.21.0


  reply index

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 ` Sean Christopherson [this message]
2019-06-10 15:06   ` [RFC PATCH v2 1/5] mm: Introduce vm_ops->may_mprotect() 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
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

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20190606021145.12604-2-sean.j.christopherson@intel.com \
    --to=sean.j.christopherson@intel.com \
    --cc=akpm@linux-foundation.org \
    --cc=andriy.shevchenko@linux.intel.com \
    --cc=bp@alien8.de \
    --cc=cedric.xing@intel.com \
    --cc=dave.hansen@intel.com \
    --cc=eparis@parisplace.org \
    --cc=haitao.huang@intel.com \
    --cc=jarkko.sakkinen@linux.intel.com \
    --cc=jethro@fortanix.com \
    --cc=jmorris@namei.org \
    --cc=josh@joshtriplett.org \
    --cc=kai.huang@intel.com \
    --cc=kai.svahn@intel.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-security-module@vger.kernel.org \
    --cc=linux-sgx@vger.kernel.org \
    --cc=luto@kernel.org \
    --cc=nhorman@redhat.com \
    --cc=npmccallum@redhat.com \
    --cc=paul@paul-moore.com \
    --cc=philip.b.tricca@intel.com \
    --cc=rientjes@google.com \
    --cc=sds@tycho.nsa.gov \
    --cc=selinux@vger.kernel.org \
    --cc=serge.ayoun@intel.com \
    --cc=serge@hallyn.com \
    --cc=shay.katz-zamir@intel.com \
    --cc=tglx@linutronix.de \
    --cc=torvalds@linux-foundation.org \
    --cc=william.c.roberts@intel.com \
    --cc=x86@kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-Security-Module Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-security-module/0 linux-security-module/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-security-module linux-security-module/ https://lore.kernel.org/linux-security-module \
		linux-security-module@vger.kernel.org linux-security-module@archiver.kernel.org
	public-inbox-index linux-security-module


Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-security-module


AGPL code for this site: git clone https://public-inbox.org/ public-inbox