[lxc-devel] [lxc/master] api-extensions: add and document cgroup_advanced_isolation

brauner on Github lxc-bot at linuxcontainers.org
Sat Apr 4 10:08:35 UTC 2020


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From 6723dcc892fd54bd56241ae7f2825a219b44e95f Mon Sep 17 00:00:00 2001
From: Christian Brauner <christian.brauner at ubuntu.com>
Date: Sat, 4 Apr 2020 12:07:43 +0200
Subject: [PATCH] api-extensions: add and document cgroup_advanced_isolation

Signed-off-by: Christian Brauner <christian.brauner at ubuntu.com>
---
 doc/api-extensions.md    | 14 ++++++++++++++
 src/lxc/api_extensions.h |  1 +
 2 files changed, 15 insertions(+)

diff --git a/doc/api-extensions.md b/doc/api-extensions.md
index 5767583af9..341ae00dee 100644
--- a/doc/api-extensions.md
+++ b/doc/api-extensions.md
@@ -118,3 +118,17 @@ This adds a new API function `init_pidfd()` which allows to retrieve a pidfd for
 ## pidfd
 
 When running on kernels that support pidfds LXC will rely on them for most operations. This makes interacting with containers not just more reliable it also makes it significantly safer and eliminates various races inherent to PID-based kernel APIs. LXC will require that the running kernel at least support `pidfd_send_signal()`, `CLONE_PIDFD`, `P_PIDFD`, and pidfd polling support. Any kernel starting with `Linux 5.4` should have full support for pidfds.
+
+## cgroup\_advanced\_isolation
+
+Privileged containers will usually be able to override the cgroup limits given
+to them. This introduces three new configuration keys `lxc.cgroup.dir.monitor`,
+`lxc.cgroup.dir.container`, and `lxc.cgroup.dir.container.inner`. The
+`lxc.cgroup.dir.monitor` and `lxc.cgroup.dir.container` keys can be used to
+set to place the `monitor` and the `container` into different cgroups. The
+`lxc.cgroup.dir.container.inner` key can be set to a cgroup that is
+concatenated with `lxc.cgroup.dir.container`. When
+`lxc.cgroup.dir.container.inner` is set the container will be placed into the
+`lxc.cgroup.dir.container.inner` cgroup but the limits will be set in the
+`lxc.cgroup.dir.container` cgroup. This way privileged containers cannot escape
+their cgroup limits.
diff --git a/src/lxc/api_extensions.h b/src/lxc/api_extensions.h
index 9ff071edf3..71931e3e21 100644
--- a/src/lxc/api_extensions.h
+++ b/src/lxc/api_extensions.h
@@ -38,6 +38,7 @@ static char *api_extensions[] = {
 	"cgroup2_devices",
 #endif
 	"cgroup2",
+	"cgroup_advanced_isolation",
 };
 
 static size_t nr_api_extensions = sizeof(api_extensions) / sizeof(*api_extensions);


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