From: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Date: Mon, 3 May 2021 16:50:25 +0000 (-0400)
Subject: Fix: lttng-ctl: erroneous check if user is part of the tracing group
X-Git-Tag: v2.13.0-rc2~38
X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=adca10efed6211c1f4c129b6233bcc96f6732364;p=lttng-tools.git

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: I614da0123d0546c5f54f121e8ed9716d6e292400
---

diff --git a/src/lib/lttng-ctl/lttng-ctl.c b/src/lib/lttng-ctl/lttng-ctl.c
index 7a38699d9..d9805e222 100644
--- a/src/lib/lttng-ctl/lttng-ctl.c
+++ b/src/lib/lttng-ctl/lttng-ctl.c
@@ -388,7 +388,7 @@ 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));