3 files changed, 93 insertions, 37 deletions

diff --git a/security/selinux/ss/mls.c b/security/selinux/ss/mls.c
index 756036bcc243..d4c32c39ccc9 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 @@ int mls_context_isvalid(struct policydb *p, struct context *c)
 }
 
 /*
+ * 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 @@ int mls_context_isvalid(struct policydb *p, struct context *c)
  *
  * 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 @@ int mls_context_to_sid(char oldc,
         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 @@ out:
 }
 
 /*
- * 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 0d37beaa85e2..03de697c8058 100644
--- a/security/selinux/ss/mls.h
+++ b/security/selinux/ss/mls.h
@@ -23,7 +23,9 @@ int mls_context_isvalid(struct policydb *p, struct context *c);
 
 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 922bb45054aa..014120474e69 100644
--- a/security/selinux/ss/services.c
+++ b/security/selinux/ss/services.c
@@ -601,18 +601,7 @@ out:
 
 }
 
-/**
- * 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 @@ int security_context_to_sid(char *scontext, u32 scontext_len, u32 *sid)
 
         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 @@ out:
         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,