Aleksa Sarai
864db8042d
These codepaths are very old and operate on pure paths but before pivot_root(2), meaning that a bad image with a malicious /dev symlink could cause us to operate on host paths instead. In practice this means that we could be tricked into removing a file called "ptmx" (note that /dev/pts/ptmx and /dev/ptmx are both immune for different reasons) or creating a very restricted set of symlinks (with fixed targets and names). The scope of these bugs is thus quite limited, but we definitely need to harden against it. These codepaths were unfortunately missed during the fd-based rework in commitd40b3439a9("rootfs: switch to fd-based handling of mountpoint targets") -- I must've assumed they were called after pivot_root(2)... Fixes: GHSA-xjvp-4fhw-gc47 Fixes: CVE-2026-41579 Fixes:d40b3439a9("rootfs: switch to fd-based handling of mountpoint targets") Signed-off-by: Aleksa Sarai <aleksa@amutable.com>
libcontainer
Libcontainer provides a native Go implementation for creating containers with namespaces, cgroups, capabilities, and filesystem access controls. It allows you to manage the lifecycle of the container performing additional operations after the container is created.
Container
A container is a self contained execution environment that shares the kernel of the host system and which is (optionally) isolated from other containers in the system.
Using libcontainer
For a brief overview of using libcontainer, see example_test.go.
Container init
Because containers are spawned in a two step process you will need a binary that will be executed as the init process for the container. In libcontainer, we use the current binary (/proc/self/exe) to be executed as the init process, and use arg "init", we call the first step process "bootstrap", so you always need a "init" function as the entry of "bootstrap".
In addition to the go init function the early stage bootstrap is handled by importing nsenter.
For details on how runc implements such "init", see ../init.go and init_linux.go.
Checkpoint & Restore
libcontainer now integrates CRIU for checkpointing and restoring containers. This lets you save the state of a process running inside a container to disk, and then restore that state into a new process, on the same machine or on another machine.
criu version 1.5.2 or higher is required to use checkpoint and restore.
If you don't already have criu installed, you can build it from source, following the
online instructions. criu is also installed in the docker image
generated when building libcontainer with docker.
Copyright and license
Code and documentation copyright 2014 Docker, inc. The code and documentation are released under the Apache 2.0 license. The documentation is also released under Creative Commons Attribution 4.0 International License. You may obtain a copy of the license, titled CC-BY-4.0, at http://creativecommons.org/licenses/by/4.0/.