apparmor: use the dfa to do label parse string splitting

The current split scheme is actually wrong in that it splits
  ///&

where that is invalid and should fail. Use the dfa to do a proper
bounded split without having to worry about getting the string
processing right in code.

Signed-off-by: John Johansen <john.johansen@canonical.com>
Acked-by: Seth Arnold <seth.arnold@canonical.com>

2 files changed, 26 insertions, 0 deletions

diff --git a/security/apparmor/include/label.h b/security/apparmor/include/label.h
index af22dcbbcb8a..80e9ba9d172c 100644
--- a/security/apparmor/include/label.h
+++ b/security/apparmor/include/label.h
@@ -330,6 +330,31 @@ void aa_label_printk(struct aa_label *label, gfp_t gfp);
 struct aa_label *aa_label_parse(struct aa_label *base, const char *str,
 				gfp_t gfp, bool create, bool force_stack);
 
+static inline const char *aa_label_strn_split(const char *str, int n)
+{
+	const char *pos;
+	unsigned int state;
+
+	state = aa_dfa_matchn_until(stacksplitdfa, DFA_START, str, n, &pos);
+	if (!ACCEPT_TABLE(stacksplitdfa)[state])
+		return NULL;
+
+	return pos - 3;
+}
+
+static inline const char *aa_label_str_split(const char *str)
+{
+	const char *pos;
+	unsigned int state;
+
+	state = aa_dfa_match_until(stacksplitdfa, DFA_START, str, &pos);
+	if (!ACCEPT_TABLE(stacksplitdfa)[state])
+		return NULL;
+
+	return pos - 3;
+}
+
+
 
 struct aa_perms;
 int aa_label_match(struct aa_profile *profile, struct aa_label *label,
diff --git a/security/apparmor/include/match.h b/security/apparmor/include/match.h
index 72b9b89670e6..cd8aeab6ac57 100644
--- a/security/apparmor/include/match.h
+++ b/security/apparmor/include/match.h
@@ -101,6 +101,7 @@ struct aa_dfa {
 };
 
 extern struct aa_dfa *nulldfa;
+extern struct aa_dfa *stacksplitdfa;
 
 #define byte_to_byte(X) (X)