[lttng-dev] [PATCH lttng-tools v2] Fix: use newly created event filter for condition check

[Jonathan Rajotte]

The following commit introduced a regression while
fixing the filter and filter_expression ownership.

commit b0a23296344e57bd2e48e62ec2d7e0d8a38661bb
Author: Jérémie Galarneau <jeremie.galarneau at efficios.com>
Date:   Sat Jan 12 14:53:56 2019 -0500

    Fix: leak of filter bytecode and expression on agent event re-enable

    The agent subsystem does not properly assume the clean-up of an
    event's filter bytecode and expression when a previously disabled
    event is re-enabled.

    This change ensures that the ownership of both the filter bytecode
    and expression is assumed by the agent subsystem and discarded
    when a matching event is found.

    Steps to reproduce the leak:
    $ lttng create
    $ lttng enable-event --python allo --filter 'a[42] == 241'
    $ lttng disable-event --python allo
    $ lttng enable-event --python allo --filter 'a[42] == 241'

    Signed-off-by: Jérémie Galarneau <jeremie.galarneau at efficios.com>

Setting the "filter" object to NULL prevents the call to
add_filter_app_ctx when needed.

We use the filter from the newly created event to
perform the check and the call to add_filter_app_ctx.

Fixes coverity #1399733

Signed-off-by: Jonathan Rajotte <jonathan.rajotte-julien at efficios.com>
---
 src/bin/lttng-sessiond/agent.c | 1 +
 src/bin/lttng-sessiond/event.c | 5 +++--
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/src/bin/lttng-sessiond/agent.c b/src/bin/lttng-sessiond/agent.c
index 9ea899f57..79233ab7c 100644
--- a/src/bin/lttng-sessiond/agent.c
+++ b/src/bin/lttng-sessiond/agent.c
@@ -1145,6 +1145,7 @@ struct agent_event *agent_create_event(const char *name,
 	event->loglevel_type = loglevel_type;
 	event->filter = filter;
 	event->filter_expression = filter_expression;
+	event->enabled = 0;
 error:
 	return event;
 }
diff --git a/src/bin/lttng-sessiond/event.c b/src/bin/lttng-sessiond/event.c
index f32db4429..a8b7646da 100644
--- a/src/bin/lttng-sessiond/event.c
+++ b/src/bin/lttng-sessiond/event.c
@@ -513,8 +513,9 @@ int event_agent_enable(struct ltt_ust_session *usess,
 		created = 1;
 	}
 
-	if (created && filter) {
-		ret = add_filter_app_ctx(filter, filter_expression, agt);
+	if (created && aevent->filter) {
+		ret = add_filter_app_ctx(
+				aevent->filter, aevent->filter_expression, agt);
 		if (ret != LTTNG_OK) {
 			goto error;
 		}
-- 
2.17.1