su: Replace STRFCPY() by STRLCPY()

The variables are only being read as strings (char *), so data after the
'\0' can't be leaked.

Cc: Christian Göttsche <cgzones@googlemail.com>
Cc: Serge Hallyn <serge@hallyn.com>
Cc: Iker Pedrosa <ipedrosa@redhat.com>
Signed-off-by: Alejandro Colomar <alx@kernel.org>

src/su.c

@@ -57,6 +57,7 @@
 /*@-exitarg@*/
 #include "exitcodes.h"
 #include "shadowlog.h"
+#include "strlcpy.h"
 
 /*
  * Global variables
@@ -777,7 +778,7 @@ static void save_caller_context (char **argv)
 		         (unsigned long) caller_uid));
 		su_failure (caller_tty, true); /* unknown target UID*/
 	}
-	STRFCPY (caller_name, pw->pw_name);
+	STRLCPY(caller_name, pw->pw_name);
 
 #ifndef USE_PAM
 #ifdef SU_ACCESS
@@ -852,7 +853,7 @@ static void process_flags (int argc, char **argv)
 	}
 
 	if (optind < argc) {
-		STRFCPY (name, argv[optind++]);	/* use this login id */
+		STRLCPY(name, argv[optind++]);	/* use this login id */
 	}
 	if ('\0' == name[0]) {		/* use default user */
 		struct passwd *root_pw = getpwnam ("root");