ima: do not measure or appraise the NSFS filesystem

Include don't appraise or measure rules for the NSFS filesystem
in the builtin ima_tcb and ima_appraise_tcb policies.

Changelog:
- Update documentation

Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
Cc: stable@vger.kernel.org # 3.19

Documentation/ABI/testing/ima_policy

@@ -65,6 +65,9 @@ Description:
 			# CGROUP_SUPER_MAGIC
 			dont_measure fsmagic=0x27e0eb
 			dont_appraise fsmagic=0x27e0eb
+			# NSFS_MAGIC
+			dont_measure fsmagic=0x6e736673
+			dont_appraise fsmagic=0x6e736673
 
 			measure func=BPRM_CHECK
 			measure func=FILE_MMAP mask=MAY_EXEC

security/integrity/ima/ima_policy.c

@@ -81,6 +81,7 @@ static struct ima_rule_entry default_rules[] = {
 	{.action = DONT_MEASURE, .fsmagic = SELINUX_MAGIC, .flags = IMA_FSMAGIC},
 	{.action = DONT_MEASURE, .fsmagic = CGROUP_SUPER_MAGIC,
 	 .flags = IMA_FSMAGIC},
+	{.action = DONT_MEASURE, .fsmagic = NSFS_MAGIC, .flags = IMA_FSMAGIC},
 	{.action = MEASURE, .func = MMAP_CHECK, .mask = MAY_EXEC,
 	 .flags = IMA_FUNC | IMA_MASK},
 	{.action = MEASURE, .func = BPRM_CHECK, .mask = MAY_EXEC,
@@ -101,6 +102,7 @@ static struct ima_rule_entry default_appraise_rules[] = {
 	{.action = DONT_APPRAISE, .fsmagic = BINFMTFS_MAGIC, .flags = IMA_FSMAGIC},
 	{.action = DONT_APPRAISE, .fsmagic = SECURITYFS_MAGIC, .flags = IMA_FSMAGIC},
 	{.action = DONT_APPRAISE, .fsmagic = SELINUX_MAGIC, .flags = IMA_FSMAGIC},
+	{.action = DONT_APPRAISE, .fsmagic = NSFS_MAGIC, .flags = IMA_FSMAGIC},
 	{.action = DONT_APPRAISE, .fsmagic = CGROUP_SUPER_MAGIC, .flags = IMA_FSMAGIC},
 #ifndef CONFIG_IMA_APPRAISE_SIGNED_INIT
 	{.action = APPRAISE, .fowner = GLOBAL_ROOT_UID, .flags = IMA_FOWNER},