From 92cc3e7f76a545a2cd4828576971f1eea83f4e68 Mon Sep 17 00:00:00 2001
From: Francis Deslauriers <francis.deslauriers@efficios.com>
Date: Wed, 17 Mar 2021 10:40:56 -0400
Subject: [PATCH 4/4] Fix: kretprobe: null ptr deref on session destroy

The `filter_bytecode_runtime_head` list is currently not initialized for
the return event of the kretprobe. This caused a kernel null ptr
dereference when destroying a session. It can reproduced with the
following commands:

  lttng create
  lttng enable-event -k --function=lttng_test_filter_event_write my_event
  lttng start
  lttng stop
  lttng destroy

Upstream-status: backport 

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I1162ce8b10dd7237a26331531f048346b984eee7
---
 lttng-events.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/lttng-events.c b/lttng-events.c
index 984bd341..3450fa40 100644
--- a/lttng-events.c
+++ b/lttng-events.c
@@ -704,6 +704,8 @@ struct lttng_event *_lttng_event_create(struct lttng_channel *chan,
 		event_return->enabled = 0;
 		event_return->registered = 1;
 		event_return->instrumentation = itype;
+		INIT_LIST_HEAD(&event_return->bytecode_runtime_head);
+		INIT_LIST_HEAD(&event_return->enablers_ref_head);
 		/*
 		 * Populate lttng_event structure before kretprobe registration.
 		 */
-- 
2.19.1