[apparmor] libappamor: Fix mode string NUL-termination of aa_getcon() functions

[Tyler Hicks]

r2125 caused a regression in aa_getpeercon_raw() when a NULL pointer was
passed into the mode parameter. Instead of unconditionally
NUL-terminating the con string before the mode portion of the security
context, it made it to where the NUL byte was only put into place when
mode was non-NULL.

This resulted in the con string incorrectly containing the label and the
mode.

fixes bug: https://launchpad.net/bugs/1220861

--- libraries/libapparmor/src/kernel_interface.c	2013-08-26 23:54:26 +0000
+++ libraries/libapparmor/src/kernel_interface.c	2013-09-04 19:01:42 +0000
@@ -194,6 +194,7 @@
 	int rc = -1;
 	int fd, ret;
 	char *tmp = NULL;
+	char *mode_str;
 	int size = 0;
 
 	if (!buf || len <= 0) {
@@ -246,8 +247,9 @@
 			size++;
 		}
 
+		mode_str = parse_confinement_mode(buf, size);
 		if (mode)
-			*mode = parse_confinement_mode(buf, size);
+			*mode = mode_str;
 	}
 	rc = size;