SELinux: allow userspace to read policy back out of the kernel

There is interest in being able to see what the actual policy is that was
loaded into the kernel.  The patch creates a new selinuxfs file
/selinux/policy which can be read by userspace.  The actual policy that is
loaded into the kernel will be written back out to userspace.

Signed-off-by: Eric Paris <eparis@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>

1 files changed, 48 insertions, 0 deletions

diff --git a/security/selinux/ss/services.c b/security/selinux/ss/services.c
index 60964d79e5eb..7565d16aac31 100644
--- a/security/selinux/ss/services.c
+++ b/security/selinux/ss/services.c
@@ -1776,6 +1776,7 @@ int security_load_policy(void *data, size_t len)
                         return rc;
                 }
 
+                policydb.len = len;
                 rc = selinux_set_mapping(&policydb, secclass_map,
                                          &current_mapping,
                                          &current_mapping_size);
@@ -1812,6 +1813,7 @@ int security_load_policy(void *data, size_t len)
         if (rc)
                 return rc;
 
+        newpolicydb.len = len;
         /* If switching between different policy types, log MLS status */
         if (policydb.mls_enabled && !newpolicydb.mls_enabled)
                 printk(KERN_INFO "SELinux: Disabling MLS support...\n");
@@ -1892,6 +1894,17 @@ err:
 
 }
 
+size_t security_policydb_len(void)
+{
+        size_t len;
+
+        read_lock(&policy_rwlock);
+        len = policydb.len;
+        read_unlock(&policy_rwlock);
+
+        return len;
+}
+
 /**
  * security_port_sid - Obtain the SID for a port.
  * @protocol: protocol number
@@ -3139,3 +3152,38 @@ netlbl_sid_to_secattr_failure:
         return rc;
 }
 #endif /* CONFIG_NETLABEL */
+
+/**
+ * security_read_policy - read the policy.
+ * @data: binary policy data
+ * @len: length of data in bytes
+ *
+ */
+int security_read_policy(void **data, ssize_t *len)
+{
+        int rc;
+        struct policy_file fp;
+
+        if (!ss_initialized)
+                return -EINVAL;
+
+        *len = security_policydb_len();
+
+        *data = vmalloc(*len);
+        if (!*data)
+                return -ENOMEM;
+
+        fp.data = *data;
+        fp.len = *len;
+
+        read_lock(&policy_rwlock);
+        rc = policydb_write(&policydb, &fp);
+        read_unlock(&policy_rwlock);
+
+        if (rc)
+                return rc;
+
+        *len = (unsigned long)fp.data - (unsigned long)*data;
+        return 0;
+
+}