apparmor: dfa split verification of table headers

separate the different types of verification so they are logically
separate and can be reused separate of each other.
Signed-off-by: John Johansen <john.johansen@canonical.com>

security/apparmor/match.c

@@ -136,8 +136,8 @@ static struct table_header *unpack_table(char *blob, size_t bsize)
 }
 
 /**
- * verify_dfa - verify that transitions and states in the tables are in bounds.
- * @dfa: dfa to test  (NOT NULL)
+ * verify_table_headers - verify that the tables headers are as expected
+ * @tables - array of dfa tables to check (NOT NULL)
  * @flags: flags controlling what type of accept table are acceptable
  *
  * Assumes dfa has gone through the first pass verification done by unpacking
@@ -145,83 +145,98 @@ static struct table_header *unpack_table(char *blob, size_t bsize)
  *
  * Returns: %0 else error code on failure to verify
  */
-static int verify_dfa(struct aa_dfa *dfa, int flags)
+static int verify_table_headers(struct table_header **tables, int flags)
 {
-	size_t i, state_count, trans_count;
+	size_t state_count, trans_count;
 	int error = -EPROTO;
 
 	/* check that required tables exist */
-	if (!(dfa->tables[YYTD_ID_DEF] &&
-	      dfa->tables[YYTD_ID_BASE] &&
-	      dfa->tables[YYTD_ID_NXT] && dfa->tables[YYTD_ID_CHK]))
+	if (!(tables[YYTD_ID_DEF] && tables[YYTD_ID_BASE] &&
+	      tables[YYTD_ID_NXT] && tables[YYTD_ID_CHK]))
 		goto out;
 
 	/* accept.size == default.size == base.size */
-	state_count = dfa->tables[YYTD_ID_BASE]->td_lolen;
+	state_count = tables[YYTD_ID_BASE]->td_lolen;
 	if (ACCEPT1_FLAGS(flags)) {
-		if (!dfa->tables[YYTD_ID_ACCEPT])
+		if (!tables[YYTD_ID_ACCEPT])
 			goto out;
-		if (state_count != dfa->tables[YYTD_ID_ACCEPT]->td_lolen)
+		if (state_count != tables[YYTD_ID_ACCEPT]->td_lolen)
 			goto out;
 	}
 	if (ACCEPT2_FLAGS(flags)) {
-		if (!dfa->tables[YYTD_ID_ACCEPT2])
+		if (!tables[YYTD_ID_ACCEPT2])
 			goto out;
-		if (state_count != dfa->tables[YYTD_ID_ACCEPT2]->td_lolen)
+		if (state_count != tables[YYTD_ID_ACCEPT2]->td_lolen)
 			goto out;
 	}
-	if (state_count != dfa->tables[YYTD_ID_DEF]->td_lolen)
+	if (state_count != tables[YYTD_ID_DEF]->td_lolen)
 		goto out;
 
 	/* next.size == chk.size */
-	trans_count = dfa->tables[YYTD_ID_NXT]->td_lolen;
-	if (trans_count != dfa->tables[YYTD_ID_CHK]->td_lolen)
+	trans_count = tables[YYTD_ID_NXT]->td_lolen;
+	if (trans_count != tables[YYTD_ID_CHK]->td_lolen)
 		goto out;
 
 	/* if equivalence classes then its table size must be 256 */
-	if (dfa->tables[YYTD_ID_EC] &&
-	    dfa->tables[YYTD_ID_EC]->td_lolen != 256)
+	if (tables[YYTD_ID_EC] && tables[YYTD_ID_EC]->td_lolen != 256)
 		goto out;
 
-	if (flags & DFA_FLAG_VERIFY_STATES) {
-		for (i = 0; i < state_count; i++) {
-			if (!(BASE_TABLE(dfa)[i] & MATCH_FLAG_DIFF_ENCODE) &&
-			    (DEFAULT_TABLE(dfa)[i] >= state_count))
-				goto out;
-			if (base_idx(BASE_TABLE(dfa)[i]) + 255 >= trans_count) {
-				printk(KERN_ERR "AppArmor DFA next/check upper "
-				       "bounds error\n");
-				goto out;
-			}
-		}
+	error = 0;
+out:
+	return error;
+}
 
-		for (i = 0; i < trans_count; i++) {
-			if (NEXT_TABLE(dfa)[i] >= state_count)
-				goto out;
-			if (CHECK_TABLE(dfa)[i] >= state_count)
-				goto out;
+/**
+ * verify_dfa - verify that transitions and states in the tables are in bounds.
+ * @dfa: dfa to test  (NOT NULL)
+ *
+ * Assumes dfa has gone through the first pass verification done by unpacking
+ * NOTE: this does not valid accept table values
+ *
+ * Returns: %0 else error code on failure to verify
+ */
+static int verify_dfa(struct aa_dfa *dfa)
+{
+	size_t i, state_count, trans_count;
+	int error = EPROTO;
+
+	state_count = dfa->tables[YYTD_ID_BASE]->td_lolen;
+	trans_count = dfa->tables[YYTD_ID_NXT]->td_lolen;
+	for (i = 0; i < state_count; i++) {
+		if (!(BASE_TABLE(dfa)[i] & MATCH_FLAG_DIFF_ENCODE) &&
+		    (DEFAULT_TABLE(dfa)[i] >= state_count))
+			goto out;
+		if (base_idx(BASE_TABLE(dfa)[i]) + 255 >= trans_count) {
+			pr_err("AppArmor DFA next/check upper bounds error\n");
+			goto out;
 		}
 	}
 
+	for (i = 0; i < trans_count; i++) {
+		if (NEXT_TABLE(dfa)[i] >= state_count)
+			goto out;
+		if (CHECK_TABLE(dfa)[i] >= state_count)
+			goto out;
+	}
+
 	/* Now that all the other tables are verified, verify diffencoding */
-	if (flags & DFA_FLAG_VERIFY_STATES) {
+	for (i = 0; i < state_count; i++) {
 		size_t j, k;
 
-		for (i = 0; i < state_count; i++) {
-			for (j = i;
-			     (BASE_TABLE(dfa)[j] & MATCH_FLAG_DIFF_ENCODE) &&
-			      !(BASE_TABLE(dfa)[j] & MARK_DIFF_ENCODE);
-			     j = k) {
-				k = DEFAULT_TABLE(dfa)[j];
-				if (j == k)
-					goto out;
-				if (k < j)
-					break;		/* already verified */
-				BASE_TABLE(dfa)[j] |= MARK_DIFF_ENCODE;
-			}
+		for (j = i;
+		     (BASE_TABLE(dfa)[j] & MATCH_FLAG_DIFF_ENCODE) &&
+		     !(BASE_TABLE(dfa)[j] & MARK_DIFF_ENCODE);
+		     j = k) {
+			k = DEFAULT_TABLE(dfa)[j];
+			if (j == k)
+				goto out;
+			if (k < j)
+				break;		/* already verified */
+			BASE_TABLE(dfa)[j] |= MARK_DIFF_ENCODE;
 		}
 	}
 	error = 0;
+
 out:
 	return error;
 }
@@ -338,11 +353,16 @@ struct aa_dfa *aa_dfa_unpack(void *blob, size_t size, int flags)
 		size -= table_size(table->td_lolen, table->td_flags);
 		table = NULL;
 	}
-
-	error = verify_dfa(dfa, flags);
+	error = verify_table_headers(dfa->tables, flags);
 	if (error)
 		goto fail;
 
+	if (flags & DFA_FLAG_VERIFY_STATES) {
+		error = verify_dfa(dfa);
+		if (error)
+			goto fail;
+	}
+
 	return dfa;
 
 fail: