9p: use copy of the options value instead of original

v9fs_parse_options function uses strsep which modifies the value of the
v9ses->options field. That modified value is later passed to the function
that creates the transport potentially making the transport creation
function to fail.

This patch creates a copy of v9ses->option field that v9fs_parse_options
function uses instead of the original value.
Signed-off-by: Latchesar Ionkov <lucho@ionkov.net>
Acked-by: Eric Van Hensbergen <ericvh@gmail.com>

fs/9p/v9fs.c

@@ -82,7 +82,7 @@ static match_table_t tokens = {
 
 static void v9fs_parse_options(struct v9fs_session_info *v9ses)
 {
-	char *options = v9ses->options;
+	char *options;
 	substring_t args[MAX_OPT_ARGS];
 	char *p;
 	int option;
@@ -96,9 +96,10 @@ static void v9fs_parse_options(struct v9fs_session_info *v9ses)
 	v9ses->cache = 0;
 	v9ses->trans = v9fs_default_trans();
 
-	if (!options)
+	if (!v9ses->options)
 		return;
 
+	options = kstrdup(v9ses->options, GFP_KERNEL);
 	while ((p = strsep(&options, ",")) != NULL) {
 		int token;
 		if (!*p)
@@ -169,6 +170,7 @@ static void v9fs_parse_options(struct v9fs_session_info *v9ses)
 			continue;
 		}
 	}
+	kfree(options);
 }
 
 /**