From 1a2af5cb8649e2b3106ee20341fc30a90e9e3bde Mon Sep 17 00:00:00 2001
From: Adrian Serrano <adrisr83@gmail.com>
Date: Mon, 28 Sep 2020 20:33:47 +0200
Subject: [PATCH] Fix panic in cgroups monitoring

Gosigar's cgroups GetStatsForProcesses can return a nil Stats pointer
and no error when the ["blkio", "cpu", "cpuacct", "memory"] subsystems
are on the root cgroup.

Related #21113
---
 libbeat/cmd/instance/metrics.go | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/libbeat/cmd/instance/metrics.go b/libbeat/cmd/instance/metrics.go
index fa0d42bbeafd..24d3d12e3e19 100644
--- a/libbeat/cmd/instance/metrics.go
+++ b/libbeat/cmd/instance/metrics.go
@@ -285,6 +285,10 @@ func reportBeatCgroups(_ monitoring.Mode, V monitoring.Visitor) {
 		logp.Err("error getting group status: %v", err)
 		return
 	}
+	// GetStatsForProcess returns a nil selfStats and no error when there's no stats
+	if selfStats == nil {
+		return
+	}
 
 	if cpu := selfStats.CPU; cpu != nil {
 		monitoring.ReportNamespace(V, "cpu", func() {