[lxc-devel] [lxc/master] cgfsng: do not reuse another monitor's cgroup

[brauner on Github]

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From ee455be41cd127dd9fb37f35a2ee826e637bb76d Mon Sep 17 00:00:00 2001
From: Christian Brauner <christian.brauner at ubuntu.com>
Date: Tue, 2 Oct 2018 17:27:55 +0200
Subject: [PATCH] cgfsng: do not reuse another monitor's cgroup

Otherwise we will create a race.

Signed-off-by: Christian Brauner <christian.brauner at ubuntu.com>
---
 src/lxc/cgroups/cgfsng.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/src/lxc/cgroups/cgfsng.c b/src/lxc/cgroups/cgfsng.c
index e248db31a..0fc9b11d2 100644
--- a/src/lxc/cgroups/cgfsng.c
+++ b/src/lxc/cgroups/cgfsng.c
@@ -1262,8 +1262,10 @@ static bool monitor_create_path_for_hierarchy(struct hierarchy *h, char *cgname)
 	int ret;
 
 	h->monitor_full_path = must_make_path(h->mountpoint, h->container_base_path, cgname, NULL);
-	if (dir_exists(h->monitor_full_path))
-		return true;
+	if (dir_exists(h->monitor_full_path)) {
+		ERROR("The cgroup \"%s\" already existed", h->monitor_full_path);
+		return false;
+	}
 
 	if (!cg_legacy_handle_cpuset_hierarchy(h, cgname)) {
 		ERROR("Failed to handle legacy cpuset controller");