Fix: lttng-ctl: erroneous check if user is part of the tracing group

in_tgroup is set to `-1` whenever the current user is not part of the
tracing group _or_ if an error occurred while looking up if the user
is part of the tracing group. In other words, the value '0' is unused.

in_tgroup must be explicitly checked against '1' and can't be assumed
to behave as a boolean value.

This is _not_ a security issue: if the user is not part of the tracing
group, she will fail to open the root session damon's socket because
of the kernel-side permission checking. However, the behaviour of the
lttng client (and error reporting) will be confusing.

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Change-Id: I1c12285fd0f42bb73c560a32a56cab03f1a5a6e1

diff --git a/src/lib/lttng-ctl/lttng-ctl.c b/src/lib/lttng-ctl/lttng-ctl.c
index c304a37dba4b269e8ac8740cdb0de93d521051a1..2c2335a28ccaef588b1b45a03ec120140aa756a5 100644 (file)
--- a/src/lib/lttng-ctl/lttng-ctl.c
+++ b/src/lib/lttng-ctl/lttng-ctl.c
@@ -367,7 +367,7 @@ static int set_session_daemon_path(void)
                in_tgroup = lttng_check_tracing_group();
        }
 
-       if ((uid == 0) || in_tgroup) {
+       if ((uid == 0) || in_tgroup == 1) {
                const int ret = lttng_strncpy(sessiond_sock_path,
                                DEFAULT_GLOBAL_CLIENT_UNIX_SOCK,
                                sizeof(sessiond_sock_path));