[RFC PATCH v4 08/12] security/selinux: Require SGX_MAPWX to map enclave page WX

From: Sean Christopherson <sean.j.christopherson@intel.com>
To: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Cc: linux-sgx@vger.kernel.org, linux-security-module@vger.kernel.org,
	selinux@vger.kernel.org,
	Bill Roberts <william.c.roberts@intel.com>,
	Casey Schaufler <casey.schaufler@intel.com>,
	James Morris <jmorris@namei.org>,
	Dave Hansen <dave.hansen@intel.com>,
	Cedric Xing <cedric.xing@intel.com>,
	Andy Lutomirski <luto@kernel.org>,
	Jethro Beekman <jethro@fortanix.com>,
	"Dr . Greg Wettstein" <greg@enjellic.com>,
	Stephen Smalley <sds@tycho.nsa.gov>
Subject: [RFC PATCH v4 08/12] security/selinux: Require SGX_MAPWX to map enclave page WX
Date: Wed, 19 Jun 2019 15:23:57 -0700	[thread overview]
Message-ID: <20190619222401.14942-9-sean.j.christopherson@intel.com> (raw)
In-Reply-To: <20190619222401.14942-1-sean.j.christopherson@intel.com>

Hook enclave_map() to require a new per-process capability, SGX_MAPWX,
when mapping an enclave as simultaneously writable and executable.
Note, @prot contains the actual protection bits that will be set by the
kernel, not the maximal protection bits specified by userspace when the
page was first loaded into the enclave.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
---
 security/selinux/hooks.c            | 21 +++++++++++++++++++++
 security/selinux/include/classmap.h |  3 ++-
 2 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 3ec702cf46ca..fc239e541b62 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -6726,6 +6726,23 @@ static void selinux_bpf_prog_free(struct bpf_prog_aux *aux)
 }
 #endif
 
+#ifdef CONFIG_INTEL_SGX
+static int selinux_enclave_map(unsigned long prot)
+{
+	const struct cred *cred = current_cred();
+	u32 sid = cred_sid(cred);
+
+	/* SGX is supported only in 64-bit kernels. */
+	WARN_ON_ONCE(!default_noexec);
+
+	if ((prot & PROT_EXEC) && (prot & PROT_WRITE))
+		return avc_has_perm(&selinux_state, sid, sid,
+				    SECCLASS_PROCESS2, PROCESS2__SGX_MAPWX,
+				    NULL);
+	return 0;
+}
+#endif
+
 struct lsm_blob_sizes selinux_blob_sizes __lsm_ro_after_init = {
 	.lbs_cred = sizeof(struct task_security_struct),
 	.lbs_file = sizeof(struct file_security_struct),
@@ -6968,6 +6985,10 @@ static struct security_hook_list selinux_hooks[] __lsm_ro_after_init = {
 	LSM_HOOK_INIT(bpf_map_free_security, selinux_bpf_map_free),
 	LSM_HOOK_INIT(bpf_prog_free_security, selinux_bpf_prog_free),
 #endif
+
+#ifdef CONFIG_INTEL_SGX
+	LSM_HOOK_INIT(enclave_map, selinux_enclave_map),
+#endif
 };
 
 static __init int selinux_init(void)
diff --git a/security/selinux/include/classmap.h b/security/selinux/include/classmap.h
index 201f7e588a29..cfd91e879bdf 100644
--- a/security/selinux/include/classmap.h
+++ b/security/selinux/include/classmap.h
@@ -51,7 +51,8 @@ struct security_class_mapping secclass_map[] = {
 	    "execmem", "execstack", "execheap", "setkeycreate",
 	    "setsockcreate", "getrlimit", NULL } },
 	{ "process2",
-	  { "nnp_transition", "nosuid_transition", NULL } },
+	  { "nnp_transition", "nosuid_transition",
+	    "sgx_mapwx", NULL } },
 	{ "system",
 	  { "ipc_info", "syslog_read", "syslog_mod",
 	    "syslog_console", "module_request", "module_load", NULL } },
-- 
2.21.0

