diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 6be2738..10fd51c 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -826,7 +826,8 @@
 			sid = sbsec->def_sid;
 			rc = 0;
 		} else {
-			rc = security_context_to_sid(context, rc, &sid);
+			rc = security_context_to_sid_default(context, rc, &sid,
+			                                     sbsec->def_sid);
 			if (rc) {
 				printk(KERN_WARNING "%s:  context_to_sid(%s) "
 				       "returned %d for dev=%s ino=%ld\n",
diff --git a/security/selinux/include/security.h b/security/selinux/include/security.h
index fa187c9a..71c0a19 100644
--- a/security/selinux/include/security.h
+++ b/security/selinux/include/security.h
@@ -65,6 +65,8 @@
 int security_context_to_sid(char *scontext, u32 scontext_len,
 	u32 *out_sid);
 
+int security_context_to_sid_default(char *scontext, u32 scontext_len, u32 *out_sid, u32 def_sid);
+
 int security_get_user_sids(u32 callsid, char *username,
 			   u32 **sids, u32 *nel);
 
diff --git a/security/selinux/ss/mls.c b/security/selinux/ss/mls.c
index 756036b..d4c32c3 100644
--- a/security/selinux/ss/mls.c
+++ b/security/selinux/ss/mls.c
@@ -15,6 +15,7 @@
 #include <linux/slab.h>
 #include <linux/string.h>
 #include <linux/errno.h>
+#include "sidtab.h"
 #include "mls.h"
 #include "policydb.h"
 #include "services.h"
@@ -208,6 +209,26 @@
 }
 
 /*
+ * Copies the MLS range from `src' into `dst'.
+ */
+static inline int mls_copy_context(struct context *dst,
+				   struct context *src)
+{
+	int l, rc = 0;
+
+	/* Copy the MLS range from the source context */
+	for (l = 0; l < 2; l++) {
+		dst->range.level[l].sens = src->range.level[l].sens;
+		rc = ebitmap_cpy(&dst->range.level[l].cat,
+				 &src->range.level[l].cat);
+		if (rc)
+			break;
+	}
+
+	return rc;
+}
+
+/*
  * Set the MLS fields in the security context structure
  * `context' based on the string representation in
  * the string `*scontext'.  Update `*scontext' to
@@ -216,10 +237,20 @@
  *
  * This function modifies the string in place, inserting
  * NULL characters to terminate the MLS fields.
+ *
+ * If a def_sid is provided and no MLS field is present,
+ * copy the MLS field of the associated default context.
+ * Used for upgraded to MLS systems where objects may lack
+ * MLS fields.
+ *
+ * Policy read-lock must be held for sidtab lookup.
+ *
  */
 int mls_context_to_sid(char oldc,
 		       char **scontext,
-		       struct context *context)
+		       struct context *context,
+		       struct sidtab *s,
+		       u32 def_sid)
 {
 
 	char delim;
@@ -231,9 +262,23 @@
 	if (!selinux_mls_enabled)
 		return 0;
 
-	/* No MLS component to the security context. */
-	if (!oldc)
+	/*
+	 * No MLS component to the security context, try and map to
+	 * default if provided.
+	 */
+	if (!oldc) {
+		struct context *defcon;
+
+		if (def_sid == SECSID_NULL)
+			goto out;
+
+		defcon = sidtab_search(s, def_sid);
+		if (!defcon)
+			goto out;
+
+		rc = mls_copy_context(context, defcon);
 		goto out;
+	}
 
 	/* Extract low sensitivity. */
 	scontextp = p = *scontext;
@@ -334,26 +379,6 @@
 }
 
 /*
- * Copies the MLS range from `src' into `dst'.
- */
-static inline int mls_copy_context(struct context *dst,
-				   struct context *src)
-{
-	int l, rc = 0;
-
-	/* Copy the MLS range from the source context */
-	for (l = 0; l < 2; l++) {
-		dst->range.level[l].sens = src->range.level[l].sens;
-		rc = ebitmap_cpy(&dst->range.level[l].cat,
-				 &src->range.level[l].cat);
-		if (rc)
-			break;
-	}
-
-	return rc;
-}
-
-/*
  * Copies the effective MLS range from `src' into `dst'.
  */
 static inline int mls_scopy_context(struct context *dst,
diff --git a/security/selinux/ss/mls.h b/security/selinux/ss/mls.h
index 0d37bea..03de697 100644
--- a/security/selinux/ss/mls.h
+++ b/security/selinux/ss/mls.h
@@ -23,7 +23,9 @@
 
 int mls_context_to_sid(char oldc,
 	               char **scontext,
-		       struct context *context);
+		       struct context *context,
+		       struct sidtab *s,
+		       u32 def_sid);
 
 int mls_convert_context(struct policydb *oldp,
 			struct policydb *newp,
diff --git a/security/selinux/ss/services.c b/security/selinux/ss/services.c
index 922bb45..0141204 100644
--- a/security/selinux/ss/services.c
+++ b/security/selinux/ss/services.c
@@ -601,18 +601,7 @@
 
 }
 
-/**
- * security_context_to_sid - Obtain a SID for a given security context.
- * @scontext: security context
- * @scontext_len: length in bytes
- * @sid: security identifier, SID
- *
- * Obtains a SID associated with the security context that
- * has the string representation specified by @scontext.
- * Returns -%EINVAL if the context is invalid, -%ENOMEM if insufficient
- * memory is available, or 0 on success.
- */
-int security_context_to_sid(char *scontext, u32 scontext_len, u32 *sid)
+static int security_context_to_sid_core(char *scontext, u32 scontext_len, u32 *sid, u32 def_sid)
 {
 	char *scontext2;
 	struct context context;
@@ -703,7 +692,7 @@
 
 	context.type = typdatum->value;
 
-	rc = mls_context_to_sid(oldc, &p, &context);
+	rc = mls_context_to_sid(oldc, &p, &context, &sidtab, def_sid);
 	if (rc)
 		goto out_unlock;
 
@@ -727,6 +716,46 @@
 	return rc;
 }
 
+/**
+ * security_context_to_sid - Obtain a SID for a given security context.
+ * @scontext: security context
+ * @scontext_len: length in bytes
+ * @sid: security identifier, SID
+ *
+ * Obtains a SID associated with the security context that
+ * has the string representation specified by @scontext.
+ * Returns -%EINVAL if the context is invalid, -%ENOMEM if insufficient
+ * memory is available, or 0 on success.
+ */
+int security_context_to_sid(char *scontext, u32 scontext_len, u32 *sid)
+{
+	return security_context_to_sid_core(scontext, scontext_len,
+	                                    sid, SECSID_NULL);
+}
+
+/**
+ * security_context_to_sid_default - Obtain a SID for a given security context,
+ * falling back to specified default if needed.
+ *
+ * @scontext: security context
+ * @scontext_len: length in bytes
+ * @sid: security identifier, SID
+ * @def_sid: default SID to assign on errror
+ *
+ * Obtains a SID associated with the security context that
+ * has the string representation specified by @scontext.
+ * The default SID is passed to the MLS layer to be used to allow
+ * kernel labeling of the MLS field if the MLS field is not present
+ * (for upgrading to MLS without full relabel).
+ * Returns -%EINVAL if the context is invalid, -%ENOMEM if insufficient
+ * memory is available, or 0 on success.
+ */
+int security_context_to_sid_default(char *scontext, u32 scontext_len, u32 *sid, u32 def_sid)
+{
+	return security_context_to_sid_core(scontext, scontext_len,
+	                                    sid, def_sid);
+}
+
 static int compute_sid_handle_invalid_context(
 	struct context *scontext,
 	struct context *tcontext,