[PATCH] libtracefs: Fix tracefs_event_enable/disable() to not have open regex

[Steven Rostedt <rostedt@goodmis.org>]

From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>

Found that calling tracefs_event_enable/disable() will match all content
of the passed in strings and not just what is passed in.

That is, if you have two events, "open" and "open2", and call

 tracefs_event_enable(NULL, NULL, "open");

it will match both the "open" event as well as the "open2" event. This is
because the regex is open ended.

To fix this, add a '^' to the beginning of the match and a '$' to the end
(if they do not already exist).

Fixes: fc94d1a8 ("libtracefs: Add tracefs_event_enable/disable() API")
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 src/tracefs-events.c | 23 ++++++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)

diff --git a/src/tracefs-events.c b/src/tracefs-events.c
index 0fef64f..b6d3136 100644
--- a/src/tracefs-events.c
+++ b/src/tracefs-events.c
@@ -828,6 +828,26 @@ static int enable_disable_all(struct tracefs_instance *instance,
 	return ret < 0 ? ret : 0;
 }
 
+static int make_regex(regex_t *re, const char *match)
+{
+	int len = strlen(match);
+	char str[len + 3];
+	char *p = &str[0];
+
+	if (!len || match[0] != '^')
+		*(p++) = '^';
+
+	strcpy(p, match);
+	p += len;
+
+	if (!len || match[len-1] != '$')
+		*(p++) = '$';
+
+	*p = '\0';
+
+	return regcomp(re, str, REG_ICASE|REG_NOSUB);
+}
+
 static int event_enable_disable(struct tracefs_instance *instance,
 				const char *system, const char *event,
 				bool enable)
@@ -847,12 +867,13 @@ static int event_enable_disable(struct tracefs_instance *instance,
 		goto out_free;
 
 	if (system) {
+		ret = make_regex(&system_re, system);
 		ret = regcomp(&system_re, system, REG_ICASE|REG_NOSUB);
 		if (ret < 0)
 			goto out_free;
 	}
 	if (event) {
-		ret = regcomp(&event_re, event, REG_ICASE|REG_NOSUB);
+		ret = make_regex(&event_re, event);
 		if (ret < 0) {
 			if (system)
 				regfree(&system_re);
-- 
2.29.2