github.com/opencontainers/runc

A plan depends as much upon execution as it does upon concept.

Changed

• libcontainer will now refuse to build without the nsenter package being correctly compiled (specifically this requires CGO to be enabled). This should avoid folks accidentally creating broken runc binaries (and incorrectly importing our internal libraries into their projects). (#3331)

He who controls the spice controls the universe.

Deprecated

• runc run/start now warns if a new container cgroup is non-empty or frozen; this warning will become an error in runc 1.2. (#3132, #3223)
• runc can only be built with Go 1.16 or later from this release onwards. (#3100, #3245, #3325)

Removed

• cgroup.GetHugePageSizes has been removed entirely, and been replaced with cgroup.HugePageSizes which is more efficient. (#3234)
• intelrdt.GetIntelRdtPath has been removed. Users who were using this function to get the intelrdt root should use the new intelrdt.Root instead. (#2920, #3239)

Added

• Add support for RDMA cgroup added in Linux 4.11. (#2883)
• runc exec now produces exit code of 255 when the exec failed. This may help in distinguishing between runc exec failures (such as invalid options, non-running container or non-existent binary etc.) and failures of the command being executed. (#3073)
• runc run: new --keep option to skip removal exited containers artefacts. This might be useful to check the state (e.g. of cgroup controllers) after the container has exited. (#2817, #2825)
• seccomp: add support for SCMP_ACT_KILL_PROCESS and SCMP_ACT_KILL_THREAD (the latter is just an alias for SCMP_ACT_KILL). (#3204)
• seccomp: add support for SCMP_ACT_NOTIFY (seccomp actions). This allows users to create sophisticated seccomp filters where syscalls can be efficiently emulated by privileged processes on the host. (#2682)
• checkpoint/restore: add an option (--lsm-mount-context) to set a different LSM mount context on restore. (#3068)
• runc releases are now cross-compiled for several architectures. Static builds for said architectures will be available for all future releases. (#3197)
• intelrdt: support ClosID parameter. (#2920)
• runc exec --cgroup: an option to specify a (non-top) in-container cgroup to use for the process being executed. (#3040, #3059)
• cgroup v1 controllers now support hybrid hierarchy (i.e. when on a cgroup v1 machine a cgroup2 filesystem is mounted to /sys/fs/cgroup/unified, runc run/exec now adds the container to the appropriate cgroup under it). (#2087, #3059)
• sysctl: allow slashes in sysctl names, to better match sysctl(8)'s behaviour. (#3254, #3257)
• mounts: add support for bind-mounts which are inaccessible after switching the user namespace. Note that this does not permit the container any additional access to the host filesystem, it simply allows containers to have bind-mounts configured for paths the user can access but have restrictive access control settings for other users. (#2576)
• Add support for recursive mount attributes using mount_setattr(2). These have the same names as the proposed mount(8) options -- just prepend r to the option name (such as rro). (#3272)
• Add runc features subcommand to allow runc users to detect what features runc has been built with. This includes critical information such as supported mount flags, hook names, and so on. Note that the output of this command is subject to change and will not be considered stable until runc 1.2 at the earliest. The runtime-spec specification for this feature is being developed in opencontainers/runtime-spec#1130. (#3296)

Changed

• system: improve performance of /proc/$pid/stat parsing. (#2696)
• cgroup2: when /sys/fs/cgroup is configured as a read-write mount, change the ownership of certain cgroup control files (as per /sys/kernel/cgroup/delegate) to allow for proper deferral to the container process. (#3057)
• docs: series of improvements to man pages to make them easier to read and use. (#3032)

libcontainer API

• internal api: remove internal error types and handling system, switch to Go wrapped errors. (#3033)
• New configs.Cgroup structure fields (#3177):
  • Systemd (whether to use systemd cgroup manager); and
  • Rootless (whether to use rootless cgroups).
• New cgroups/manager package aiming to simplify cgroup manager instantiation. (#3177)
• All cgroup managers' instantiation methods now initialize cgroup paths and can return errors. This allows to use any cgroup manager method (e.g. Exists, Destroy, Set, GetStats) right after instantiation, which was not possible before (as paths were initialized in Apply only). (#3178)

Fixed

• nsenter: do not try to close already-closed fds during container setup and bail on close(2) failures. (#3058)
• runc checkpoint/restore: fixed for containers with an external bind mount which destination is a symlink. (#3047).
• cgroup: improve openat2 handling for cgroup directory handle hardening. (#3030)
• runc delete -f now succeeds (rather than timing out) on a paused container. (#3134)
• runc run/start/exec now refuses a frozen cgroup (paused container in case of exec). Users can disable this using --ignore-paused. (#3132, #3223)
• config: do not permit null bytes in mount fields. (#3287)

If you were waiting for the opportune moment, that was it.

Security

• A potential vulnerability was discovered in runc (related to an internal usage of netlink), however upon further investigation we discovered that while this bug was exploitable on the master branch of runc, no released version of runc could be exploited using this bug. The exploit required being able to create a netlink attribute with a length that would overflow a uint16 but this was not possible in any released version of runc. For more information, see GHSA-v95c-p5hm-xq8f and CVE-2021-43784.

Fixed

• Fixed inability to start a container with read-write bind mount of a read-only fuse host mount. (#3283, #3292)
• Fixed inability to start when read-only /dev in set in spec. (#3276, #3277)
• Fixed not removing sub-cgroups upon container delete, when rootless cgroup v2 is used with older systemd. (#3226, #3297)
• Fixed returning error from GetStats when hugetlb is unsupported (which causes excessive logging for Kubernetes). (#3233, #3295)
• Improved an error message when dbus-user-session is not installed and rootless + cgroup2 + systemd are used. (#3212)

Given the right lever, you can move a planet.

Changed

• Made release builds reproducible from now on. (#3099, #3142)

Fixed

• Fixed a failure to set CPU quota period in some cases on cgroup v1. (#3090 #3115)
• Fixed the inability to start a container with the "adding seccomp filter rule for syscall ..." error, caused by redundant seccomp rules (i.e. those that has action equal to the default one). Such redundant rules are now skipped. (#3109, #3129)
• Fixed a rare debug log race in runc init, which can result in occasional harmful "failed to decode ..." errors from runc run or exec. (#3120, #3130)
• Fixed the check in cgroup v1 systemd manager if a container needs to be frozen before Set, and add a setting to skip such freeze unconditionally. The previous fix for that issue, done in runc 1.0.1, was not working. (#3166, #3167)

If in doubt, Meriadoc, always follow your nose.

Fixed

• Fixed occasional runc exec/run failure ("interrupted system call") on an Azure volume. (#3045, #3074)
• Fixed "unable to find groups ... token too long" error with /etc/group containing lines longer than 64K characters. (#3062, #3079)
• cgroup/systemd/v1: fix leaving cgroup frozen after Set if a parent cgroup is frozen. This is a regression in 1.0.0, not affecting runc itself but some of libcontainer users (e.g Kubernetes). (#3081, #3085)
• cgroupv2: bpf: Ignore inaccessible existing programs in case of permission error when handling replacement of existing bpf cgroup programs. This fixes a regression in 1.0.0, where some SELinux policies would block runc from being able to run entirely. (#3055, #3087)
• cgroup/systemd/v2: don't freeze cgroup on Set. (#3067, #3092)
• cgroup/systemd/v1: avoid unnecessary freeze on Set. (#3082, #3093)