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>

5 files changed, 170 insertions, 11 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)
 
diff --git a/security/apparmor/label.c b/security/apparmor/label.c
index 324fe5c60f87..31e2f701d971 100644
--- a/security/apparmor/label.c
+++ b/security/apparmor/label.c
@@ -1815,7 +1815,9 @@ static int label_count_str_entries(const char *str)
 
 	AA_BUG(!str);
 
-	for (split = strstr(str, "//&"); split; split = strstr(str, "//&")) {
+	for (split = aa_label_str_split(str);
+	     split;
+	     split = aa_label_str_split(str)) {
 		count++;
 		str = split + 3;
 	}
@@ -1859,7 +1861,7 @@ struct aa_label *aa_label_parse(struct aa_label *base, const char *str,
 	DEFINE_VEC(profile, vec);
 	struct aa_label *label, *currbase = base;
 	int i, len, stack = 0, error;
-	char *split;
+	const char *split;
 
 	AA_BUG(!base);
 	AA_BUG(!str);
@@ -1883,7 +1885,8 @@ struct aa_label *aa_label_parse(struct aa_label *base, const char *str,
 	for (i = 0; i < stack; i++)
 		vec[i] = aa_get_profile(base->vec[i]);
 
-	for (split = strstr(str, "//&"), i = stack; split && i < len; i++) {
+	for (split = aa_label_str_split(str), i = stack;
+	     split && i < len; i++) {
 		vec[i] = fqlookupn_profile(base, currbase, str, split - str);
 		if (!vec[i])
 			goto fail;
@@ -1894,7 +1897,7 @@ struct aa_label *aa_label_parse(struct aa_label *base, const char *str,
 		if (vec[i]->ns != labels_ns(currbase))
 			currbase = &vec[i]->label;
 		str = split + 3;
-		split = strstr(str, "//&");
+		split = aa_label_str_split(str);
 	}
 	/* last element doesn't have a split */
 	if (i < len) {
@@ -1930,7 +1933,6 @@ fail:
 	goto out;
 }
 
-
 /**
  * aa_labelset_destroy - remove all labels from the label set
  * @ls: label set to cleanup (NOT NULL)
diff --git a/security/apparmor/match.c b/security/apparmor/match.c
index 6c6dc1a22f9a..5d95caeddebc 100644
--- a/security/apparmor/match.c
+++ b/security/apparmor/match.c
@@ -30,6 +30,11 @@ static char nulldfa_src[] = {
 };
 struct aa_dfa *nulldfa;
 
+static char stacksplitdfa_src[] = {
+	#include "stacksplitdfa.in"
+};
+struct aa_dfa *stacksplitdfa;
+
 int aa_setup_dfa_engine(void)
 {
 	int error;
@@ -37,19 +42,31 @@ int aa_setup_dfa_engine(void)
 	nulldfa = aa_dfa_unpack(nulldfa_src, sizeof(nulldfa_src),
 				TO_ACCEPT1_FLAG(YYTD_DATA32) |
 				TO_ACCEPT2_FLAG(YYTD_DATA32));
-	if (!IS_ERR(nulldfa))
-		return 0;
+	if (IS_ERR(nulldfa)) {
+		error = PTR_ERR(nulldfa);
+		nulldfa = NULL;
+		return error;
+	}
 
-	error = PTR_ERR(nulldfa);
-	nulldfa = NULL;
+	stacksplitdfa = aa_dfa_unpack(stacksplitdfa_src,
+				      sizeof(stacksplitdfa_src),
+				      TO_ACCEPT1_FLAG(YYTD_DATA32) |
+				      TO_ACCEPT2_FLAG(YYTD_DATA32));
+	if (IS_ERR(stacksplitdfa)) {
+		aa_put_dfa(nulldfa);
+		nulldfa = NULL;
+		error = PTR_ERR(stacksplitdfa);
+		stacksplitdfa = NULL;
+		return error;
+	}
 
-	return error;
+	return 0;
 }
 
 void aa_teardown_dfa_engine(void)
 {
+	aa_put_dfa(stacksplitdfa);
 	aa_put_dfa(nulldfa);
-	nulldfa = NULL;
 }
 
 /**
diff --git a/security/apparmor/stacksplitdfa.in b/security/apparmor/stacksplitdfa.in
new file mode 100644
index 000000000000..4bddd10b62a9
--- /dev/null
+++ b/security/apparmor/stacksplitdfa.in
@@ -0,0 +1,114 @@
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