9p: strlen() doesn't count the terminator

commit 5c4bfa17 upstream.

This is an off by one bug because strlen() doesn't count the NULL
terminator.  We strcpy() addr into a fixed length array of size
UNIX_PATH_MAX later on.

The addr variable is the name of the device being mounted.
Signed-off-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

net/9p/trans_fd.c

@@ -948,7 +948,7 @@ p9_fd_create_unix(struct p9_client *client, const char *addr, char *args)
 
 	csocket = NULL;
 
-	if (strlen(addr) > UNIX_PATH_MAX) {
+	if (strlen(addr) >= UNIX_PATH_MAX) {
 		P9_EPRINTK(KERN_ERR, "p9_trans_unix: address too long: %s\n",
 			addr);
 		return -ENAMETOOLONG;