runc v1.2.3 -- "Winter is not a season, it's a celebration."

This is the third patch release of the 1.2.z release branch of runc. It
primarily fixes some minor regressions introduced in 1.2.0.

• Fixed a regression in use of securejoin.MkdirAll, where multiple
  runc processes racing to create the same mountpoint in a shared rootfs
  would result in spurious EEXIST errors. In particular, this regression
  caused issues with BuildKit. (#4543, #4550)
• Fixed a regression in eBPF support for pre-5.6 kernels after upgrading
  Cilium's eBPF library version to 0.16 in runc. (#3008, #4551)

Static Linking Notices

The runc binary distributed with this release are statically linked with
the following GNU LGPL-2.1 licensed libraries, with runc acting
as a "work that uses the Library":

• libseccomp

The versions of these libraries were not modified from their upstream versions,
but in order to comply with the LGPL-2.1 (§6(a)), we have attached the
complete source code for those libraries which (when combined with the attached
runc source code) may be used to exercise your rights under the LGPL-2.1.

However we strongly suggest that you make use of your distribution's packages
or download them from the authoritative upstream sources, especially since
these libraries are related to the security of your containers.

---

Thanks to all of the contributors who made this release possible:

• Aleksa Sarai cyphar@cyphar.com
• Kir Kolyshkin kolyshkin@gmail.com
• lifubang lifubang@acmcoder.com

Signed-off-by: Aleksa Sarai cyphar@cyphar.com

runc v1.2.2 -- "Specialization is for insects."

This is the second patch release of the 1.2.z branch of runc. It
includes two fixes for problems introduced in runc 1.2.0, as well as
some documentation improvements surrounding the overlayfs /proc/self/exe
protections.

• Fixed the failure of runc delete on a rootless container with no
  dedicated cgroup on a system with read-only /sys/fs/cgroup mount.
  This is a regression in runc 1.2.0, causing a failure when using
  rootless buildkit. (#4518, #4531)
• Using runc on a system where /run/runc and /usr/bin are on different
  filesystems no longer results in harmless but annoying messages
  ("overlayfs: "xino" feature enabled using 3 upper inode bits")
  appearing in the kernel log. (#4508, #4530)
• Better memfd-bind documentation. (#4530)
• CI: bump Fedora 40 -> 41. (#4528)

Static Linking Notices

The runc binary distributed with this release are statically linked with
the following GNU LGPL-2.1 licensed libraries, with runc acting
as a "work that uses the Library":

• libseccomp

The versions of these libraries were not modified from their upstream versions,
but in order to comply with the LGPL-2.1 (§6(a)), we have attached the
complete source code for those libraries which (when combined with the attached
runc source code) may be used to exercise your rights under the LGPL-2.1.

However we strongly suggest that you make use of your distribution's packages
or download them from the authoritative upstream sources, especially since
these libraries are related to the security of your containers.

---

Thanks to all of the contributors who made this release possible:

• Akihiro Suda akihiro.suda.cz@hco.ntt.co.jp
• Aleksa Sarai cyphar@cyphar.com
• Austin Vazquez macedonv@amazon.com
• Kir Kolyshkin kolyshkin@gmail.com
• Rodrigo Campos rodrigoca@microsoft.com
• lfbzhm lifubang@acmcoder.com

Signed-off-by: Aleksa Sarai cyphar@cyphar.com

runc v1.2.1 -- "No existe una escuela que enseñe a vivir."

This is the first patch release of the 1.2.z series of runc. It includes
a critical bugfix for an issue that manifested on SELinux-based
distributions and was blocking containerd from updating to
runc 1.2.z.

In addition, runc-dmz (added in 1.2.0) has been removed entirely. This
was opt-in (due to the many limitations it had), but the late addition
of the overlayfs-based CVE-2019-5736 protection made it no longer
necessary at all.

• We now explicitly become root after joining an existing user namespace.
  Otherwise, runc won't have permissions to configure some mounts when
  running under SELinux and runc is not creating the user namespace.
  (#4466, #4477)

• Remove dependency on golang.org/x/sys/execabs from go.mod. (#4480)
• Remove runc-dmz, that had many limitations, and is mostly made obsolete by
  the new protection mechanism added in v1.2.0. Note that runc-dmz was only
  available only in the 1.2.0 release and required to set an environment variable
  to opt-in. (#4488)

• The script/check-config.sh script now checks for overlayfs support. (#4494)
• When using cgroups v2, allow to set or update memory limit to "unlimited"
  and swap limit to a specific value. (#4501)

Static Linking Notices

The runc binary distributed with this release are statically linked with
the following GNU LGPL-2.1 licensed libraries, with runc acting
as a "work that uses the Library":

• libseccomp

The versions of these libraries were not modified from their upstream versions,
but in order to comply with the LGPL-2.1 (§6(a)), we have attached the
complete source code for those libraries which (when combined with the attached
runc source code) may be used to exercise your rights under the LGPL-2.1.

However we strongly suggest that you make use of your distribution's packages
or download them from the authoritative upstream sources, especially since
these libraries are related to the security of your containers.

---

Thanks to all of the contributors who made this release possible:

• Akihiro Suda akihiro.suda.cz@hco.ntt.co.jp
• Aleksa Sarai cyphar@cyphar.com
• Kir Kolyshkin kolyshkin@gmail.com
• Rodrigo Campos rodrigoca@microsoft.com
• Wei Fu fuweid89@gmail.com
• lifubang lifubang@acmcoder.com

Signed-off-by: Aleksa Sarai cyphar@cyphar.com

runc v1.2.0 -- "できるときにできることをやるんだ。それが今だ。"

This is the long-awaited release of runc 1.2.0! The primary changes from rc3
are general improvements and fixes for minor regressions related to the
new /proc/self/exe cloning logic in runc 1.2, follow-on patches related
to CVE-2024-45310, as well as some other minor changes.

• In order to alleviate the remaining concerns around the memory usage and
  (arguably somewhat unimportant, but measurable) performance overhead of
  memfds for cloning /proc/self/exe, we have added a new protection using
  overlayfs that is used if you have enough privileges and the running
  kernel supports it. It has effectively no performance nor memory overhead
  (compared to no cloning at all). (#4448)
• The original fix for CVE-2024-45310 was intentionally very
  limited in scope to make it easier to review, however it also did not handle
  all possible os.MkdirAll cases and thus could lead to regressions. We have
  switched to the more complete implementation in the newer versions of
  github.com/cyphar/filepath-securejoin. (#4393, #4400, #4421, #4430)
• In certain situations (a system with lots of mounts or racing mounts) we
  could accidentally end up leaking mounts from the container into the host.
  This has been fixed. (#4417)
• The fallback logic for O_TMPFILE clones of /proc/self/exe had a minor
  bug that would cause us to miss non-noexec directories and thus fail to
  start containers on some systems. (#4444)
• Sometimes the cloned /proc/self/exe file descriptor could be placed in a
  way that it would get clobbered by the Go runtime. We had a fix for this
  already but it turns out it could still break in rare circumstances, but it
  has now been fixed. (#4294, #4452)
• It is not possible for runc kill to work properly in some specific
  configurations (such as rootless containers with no cgroups and a shared pid
  namespace). We now output a warning for such configurations. (#4398)
• memfd-bind: update the documentation and make path handling with the systemd
  unit more idiomatic. (#4428)
• We now use v0.16 of Cilium's eBPF library, including fixes that quite a few
  downstreams asked for. (#4397, #4396)
• Some internal runc init synchronisation that was no longer necessary (due
  to the /proc/self/exe cloning move to Go) was removed. (#4441)

Static Linking Notices

The runc binary distributed with this release are statically linked with
the following GNU LGPL-2.1 licensed libraries, with runc acting
as a "work that uses the Library":

• libseccomp

The versions of these libraries were not modified from their upstream versions,
but in order to comply with the LGPL-2.1 (§6(a)), we have attached the
complete source code for those libraries which (when combined with the attached
runc source code) may be used to exercise your rights under the LGPL-2.1.

However we strongly suggest that you make use of your distribution's packages
or download them from the authoritative upstream sources, especially since
these libraries are related to the security of your containers.

---

Thanks to all of the contributors who made this release possible:

• Akhil Mohan akhilerm@gmail.com
• Akihiro Suda akihiro.suda.cz@hco.ntt.co.jp
• Aleksa Sarai cyphar@cyphar.com
• Amir M. Ghazanfari a.m.ghazanfari76@gmail.com
• Kir Kolyshkin kolyshkin@gmail.com
• Rafael Roquetto rafael.roquetto@grafana.com
• Rodrigo Campos rodrigoca@microsoft.com
• Sebastiaan van Stijn github@gone.nl
• Stavros Panakakis stavrospanakakis@gmail.com
• lifubang lifubang@acmcoder.com

Signed-off-by: Aleksa Sarai cyphar@cyphar.com

v1.1.15 -- "How, dear sir, did you cross the flood? By not stopping, friend, and by not straining I crossed the flood."

This is the fifteenth patch release in the 1.1.z release branch of runc.
It fixes a few issues with seccomp, leaked mounts, and system performance.

• The -ENOSYS seccomp stub is now always generated for the native
  architecture that runc is running on. This is needed to work around some
  arguably specification-incompliant behaviour from Docker on architectures
  such as ppc64le, where the allowed architecture list is set to null. This
  ensures that we always generate at least one -ENOSYS stub for the native
  architecture even with these weird configs. (#4391)
• On a system with older kernel, reading /proc/self/mountinfo may skip some
  entries, as a consequence runc may not properly set mount propagation,
  causing container mounts leak onto the host mount namespace. (#2404, #4425)
• In order to fix performance issues in the "lightweight" bindfd protection
  against [CVE-2019-5736], the temporary ro bind-mount of /proc/self/exe
  has been removed. runc now creates a binary copy in all cases. (#4392, #2532)

Static Linking Notices

The runc binary distributed with this release are statically linked with
the following GNU LGPL-2.1 licensed libraries, with runc acting
as a "work that uses the Library":

• libseccomp

The versions of these libraries were not modified from their upstream versions,
but in order to comply with the LGPL-2.1 (§6(a)), we have attached the
complete source code for those libraries which (when combined with the attached
runc source code) may be used to exercise your rights under the LGPL-2.1.

However we strongly suggest that you make use of your distribution's packages
or download them from the authoritative upstream sources, especially since
these libraries are related to the security of your containers.

---

Thanks to all of the contributors who made this release possible:

• Akihiro Suda akihiro.suda.cz@hco.ntt.co.jp
• Aleksa Sarai cyphar@cyphar.com
• Kir Kolyshkin kolyshkin@gmail.com
• lifubang lifubang@acmcoder.com
• Rodrigo Campos rodrigoca@microsoft.com

runc v1.2.0-rc.3 -- "The supreme happiness of life is the conviction that we are loved."

This is the third release candidate for the 1.2.0 branch of runc. It includes
all patches and bugfixes included in runc 1.1 patch releases (up to and
including 1.1.14) and also includes a fix for a low severity security issue
(CVE-2024-45310).

• Fix CVE-2024-45310, a low-severity attack that allowed
  maliciously configured containers to create empty files and directories on
  the host.
• Document build prerequisites for different platforms. (#4353)
• Try to delete exec fifo file when failure in creation. (#4319)
• Revert "libcontainer: seccomp: pass around *os.File for notifyfd". (#4337)
• Fix link to gvariant documentation in systemd docs. (#4369)
• Remove pre-go1.17 build-tags. (#4329)
• libct/userns: assorted (godoc) improvements. (#4330)
• libct/userns: split userns detection from internal userns code. (#4331)
• rootfs: consolidate mountpoint creation logic. (#4359)
• Add Go 1.23, drop 1.21. (#4360)
• Revert "allow overriding VERSION value in Makefile" and add EXTRA_VERSION.
  (#4370)
• Mv contrib/cmd tests/cmd (except memfd-bind). (#4377)
• Makefile: Don't read COMMIT, BUILDTAGS, EXTRA_BUILDTAGS from env vars.
  (#4380)

Static Linking Notices

The runc binary distributed with this release are statically linked with
the following GNU LGPL-2.1 licensed libraries, with runc acting
as a "work that uses the Library":

• libseccomp

The versions of these libraries were not modified from their upstream versions,
but in order to comply with the LGPL-2.1 (§6(a)), we have attached the
complete source code for those libraries which (when combined with the attached
runc source code) may be used to exercise your rights under the LGPL-2.1.

However we strongly suggest that you make use of your distribution's packages
or download them from the authoritative upstream sources, especially since
these libraries are related to the security of your containers.

---

Thanks to all of the contributors who made this release possible:

• Akihiro Suda akihiro.suda.cz@hco.ntt.co.jp
• Aleksa Sarai cyphar@cyphar.com
• Avi Deitcher avi@deitcher.net
• Kir Kolyshkin kolyshkin@gmail.com
• Rodrigo Campos rodrigoca@microsoft.com
• Sebastiaan van Stijn github@gone.nl
• lifubang lifubang@acmcoder.com
• ver4a verca@uncontrol.me

Signed-off-by: Aleksa Sarai cyphar@cyphar.com

runc v1.1.14 -- "年を取っていいことは、驚かなくなることね。"

This is the fourteenth patch release in the 1.1.z release branch of
runc. It includes a fix for a low severity security issue
(CVE-2024-45310) as well as some minor build-related fixes (including Go
1.23 support).

• Fix CVE-2024-45310, a low-severity attack that allowed
  maliciously configured containers to create empty files and directories on
  the host.
• Add support for Go 1.23. (#4360, #4372)
• Revert "allow overriding VERSION value in Makefile" and add EXTRA_VERSION.
  (#4370, #4382)
• rootfs: consolidate mountpoint creation logic. (#4359)

Static Linking Notices

The runc binary distributed with this release are statically linked with
the following GNU LGPL-2.1 licensed libraries, with runc acting
as a "work that uses the Library":

• libseccomp

The versions of these libraries were not modified from their upstream versions,
but in order to comply with the LGPL-2.1 (§6(a)), we have attached the
complete source code for those libraries which (when combined with the attached
runc source code) may be used to exercise your rights under the LGPL-2.1.

However we strongly suggest that you make use of your distribution's packages
or download them from the authoritative upstream sources, especially since
these libraries are related to the security of your containers.

---

Thanks to all of the contributors who made this release possible:

• Akihiro Suda akihiro.suda.cz@hco.ntt.co.jp
• Aleksa Sarai cyphar@cyphar.com
• Kir Kolyshkin kolyshkin@gmail.com
• Rodrigo Campos rodrigoca@microsoft.com
• Sebastiaan van Stijn thaJeztah@users.noreply.github.com
• lifubang lifubang@acmcoder.com

Signed-off-by: Aleksa Sarai cyphar@cyphar.com

runc v1.2.0-rc.2 -- "TRUE or FALSE, it's a problem!"

This is the second release candidate for the 1.2.0 branch of runc. It includes
all patches and bugfixes included in runc 1.1 patch releases (up to and
including 1.1.13). A fair few new features have been added, and some changes
have been made which may affect users. Please help us thoroughly test this
release candidate before we release 1.2.0.

Breaking

• runc now requires a minimum of Go 1.20 to compile. If building with
  Go 1.22, make sure to use 1.22.4 or later version (#4233).
• libcontainer/cgroups users who want to manage cgroup devices need to
  explicitly import libcontainer/cgroups/devices. (#3452, #4248)

Security

• The runc binaries provided here were built with go1.21.11, which includes a
  security fix for os.RemoveAll to fix a bug that would allow an attacker to
  trick runc into deleting a directory on the host. We encourage users to update,
  and if they build runc themselves, make sure they build their binaries using
  go1.21.11 or later, or go1.22.4 or later.

Added

• CI: add actuated-arm64. (#4142, #4252, #4276)

Fixed

• cgroup v2: do not set swap to 0 or unlimited when it's not available. (#4188)
• Set the default value of CpuBurst to nil instead of 0. (#4210, #4211)
• libct/cg: write unified resources line by line. (#4186)
• libct.Start: fix locking, do not allow a second container init. (#4271)
• Fix tests in debian testing (mount_sshfs.bats). (#4245)
• libct/cg/dev: fix TestSetV1Allow panic. (#4295)
• tests/int/scheduler: require smp. (#4298)

Changed

• libct/cg/fs: don't write cpu_burst twice on ENOENT. (#4259)
• Make trimpath optional. (#3908)
• Remove unused system.Execv. (#4268)
• Stop blacklisting Go 1.22+, drop Go < 1.21 support, use Go 1.22 in CI. (#4292)
• Improve some error messages for runc exec. (#4320)
• ci/gha: bump golangci-lint[-action]. (#4255)
• tests/int/tty: increase the timeout. (#4260)
• [ci] use go mod instead of go get in spec.bats. (#4264)
• tests/int/checkpoint: rm double logging. (#4251)
• ci/gha: bump golangci-lint-action from 5 to 6. (#4275)
• .cirrus.yml: rm FIXME from rootless fs on CentOS 7. (#4279)
• Dockerfile: bump Debian to 12, Go to 1.21. (#4296)
• ci/gha: switch to ubuntu 24.04. (#4286)
• Vagrantfile.fedora: bump to F40. (#4285)

Static Linking Notices

The runc binary distributed with this release are statically linked with
the following GNU LGPL-2.1 licensed libraries, with runc acting
as a "work that uses the Library":

• libseccomp

The versions of these libraries were not modified from their upstream versions,
but in order to comply with the LGPL-2.1 (§6(a)), we have attached the
complete source code for those libraries which (when combined with the attached
runc source code) may be used to exercise your rights under the LGPL-2.1.

However we strongly suggest that you make use of your distribution's packages
or download them from the authoritative upstream sources, especially since
these libraries are related to the security of your containers.

---

Thanks to the following contributors for making this release possible:

• Akhil Mohan akhilerm@gmail.com
• Akihiro Suda akihiro.suda.cz@hco.ntt.co.jp
• Aleksa Sarai cyphar@cyphar.com
• Austin Vazquez macedonv@amazon.com
• Avi Deitcher avi@deitcher.net
• Kir Kolyshkin kolyshkin@gmail.com
• Rodrigo Campos rodrigoca@microsoft.com
• Sebastiaan van Stijn thaJeztah@users.noreply.github.com
• Sohan Kunkerkar sohank2602@gmail.com
• lifubang lifubang@acmcoder.com
• ls-ggg 335814617@qq.com

runc 1.1.13 -- "There is no certainty in the world. This is the only certainty I have."

This is the thirteenth patch release in the 1.1.z release branch of runc. It
brings in Go 1.22.x compatibility and fixes a few issues, including an
occasional wrong nofile rlimit in runc exec, and a race between runc list and
runc delete.

NOTE that if using Go 1.22.x to build runc, make sure to use 1.22.4 or a later version.
For more details, see issue #4233.

• Support go 1.22.4+. (#4313)
• runc list: fix race with runc delete. (#4231)
• Fix set nofile rlimit error. (#4277, #4299)
• libct/cg/fs: fix setting rt_period vs rt_runtime. (#4284)
• Fix a debug msg for user ns in nsexec. (#4315)
• script/*: fix gpg usage wrt keyboxd. (#4316)
• CI fixes and misc backports. (#4241)
• Fix codespell warnings. (#4300)
• Silence security false positives from golang/net. (#4244)
• libcontainer: allow containers to make apps think fips is enabled/disabled for testing. (#4257)
• allow overriding VERSION value in Makefile. (#4270)
• Vagrantfile.fedora: bump Fedora to 39. (#4261)
• ci/cirrus: rm centos stream 8. (#4305, #4308)

Security

• The runc binaries provided here were built with go1.21.11, which includes a
  security fix for os.RemoveAll to fix a bug that would allow an attacker to
  trick runc into deleting a directory on the host. We encourage users to update,
  and if they build runc themselves, make sure they build their binaries using
  go1.21.11 or later, or go1.22.4 or later.

Static Linking Notices

The runc binary distributed with this release are statically linked with
the following GNU LGPL-2.1 licensed libraries, with runc acting
as a "work that uses the Library":

• libseccomp

The versions of these libraries were not modified from their upstream versions,
but in order to comply with the LGPL-2.1 (§6(a)), we have attached the
complete source code for those libraries which (when combined with the attached
runc source code) may be used to exercise your rights under the LGPL-2.1.

However we strongly suggest that you make use of your distribution's packages
or download them from the authoritative upstream sources, especially since
these libraries are related to the security of your containers.

---

Thanks to all of the contributors who made this release possible:

• Akhil Mohan akhilerm@gmail.com
• Akihiro Suda akihiro.suda.cz@hco.ntt.co.jp
• Aleksa Sarai cyphar@cyphar.com
• Kir Kolyshkin kolyshkin@gmail.com
• Sohan Kunkerkar sohank2602@gmail.com
• TTFISH jiongchiyu@gmail.com
• kychen kychen@alauda.io
• lifubang lifubang@acmcoder.com
• ls-ggg 335814617@qq.com

Signed-off-by: Kir Kolyshkin kolyshkin@gmail.com

runc 1.2.0-rc.1 -- "There's a frood who really knows where his towel is."

This is the first release candidate for the 1.2.0 branch of runc. It includes
all patches and bugfixes included in runc 1.1 patch releases (up to and
including 1.1.12). A fair few new features have been added, and some changes
have been made which may affect users. Please help us thoroughly test this
release before we release 1.2.0.

runc now requires a minimum of Go 1.20 to compile.

NOTE: runc currently will not work properly when compiled with Go 1.22 or
newer. This is due to some unfortunate glibc behaviour that Go 1.22
exacerbates in a way that results in containers not being able to start on
some systems. See this issue for more information.

Breaking

• Several aspects of how mount options work has been adjusted in a way that
  could theoretically break users that have very strange mount option strings.
  This was necessary to fix glaring issues in how mount options were being
  treated. The key changes are:

  • Mount options on bind-mounts that clear a mount flag are now always
    applied. Previously, if a user requested a bind-mount with only clearing
    options (such as rw,exec,dev) the options would be ignored and the
    original bind-mount options would be set. Unfortunately this also means
    that container configurations which specified only clearing mount options
    will now actually get what they asked for, which could break existing
    containers (though it seems unlikely that a user who requested a specific
    mount option would consider it "broken" to get the mount options they
    asked foruser who requested a specific mount option would consider it
    "broken" to get the mount options they asked for). This also allows us to
    silently add locked mount flags the user did not explicitly request to be
    cleared in rootless mode, allowing for easier use of bind-mounts for
    rootless containers. (#3967)

  • Container configurations using bind-mounts with superblock mount flags
    (i.e. filesystem-specific mount flags, referred to as "data" in
    mount(2), as opposed to VFS generic mount flags like MS_NODEV) will
    now return an error. This is because superblock mount flags will also
    affect the host mount (as the superblock is shared when bind-mounting),
    which is obviously not acceptable. Previously, these flags were silently
    ignored so this change simply tells users that runc cannot fulfil their
    request rather than just ignoring it. (#3990)

  If any of these changes cause problems in real-world workloads, please open
  an issue so we
  can adjust the behaviour to avoid compatibility issues.

Added

• runc has been updated to OCI runtime-spec 1.2.0, and supports all Linux
  features with a few minor exceptions. See
  docs/spec-conformance.md
  for more details.
• runc now supports id-mapped mounts for bind-mounts (with no restrictions on
  the mapping used for each mount). Other mount types are not currently
  supported. This feature requires MOUNT_ATTR_IDMAP kernel support (Linux
  5.12 or newer) as well as kernel support for the underlying filesystem used
  for the bind-mount. See mount_setattr(2) for a list of
  supported filesystems and other restrictions. (#3717, #3985, #3993)
• Two new mechanisms for reducing the memory usage of our protections against
  CVE-2019-5736 have been introduced:
  • runc-dmz is a minimal binary (~8K) which acts as an additional execve
    stage, allowing us to only need to protect the smaller binary. It should
    be noted that there have been several compatibility issues reported with
    the usage of runc-dmz (namely related to capabilities and SELinux). As
    such, this mechanism is opt-in and can be enabled by running runc
    with the environment variable RUNC_DMZ=true (setting this environment
    variable in config.json will have no effect). This feature can be
    disabled at build time using the runc_nodmz build tag. (#3983, #3987)
  • contrib/memfd-bind is a helper daemon which will bind-mount a memfd copy
    of /usr/bin/runc on top of /usr/bin/runc. This entirely eliminates
    per-container copies of the binary, but requires care to ensure that
    upgrades to runc are handled properly, and requires a long-running daemon
    (unfortunately memfds cannot be bind-mounted directly and thus require a
    daemon to keep them alive). (#3987)
• runc will now use cgroup.kill if available to kill all processes in a
  container (such as when doing runc kill). (#3135, #3825)
• Add support for setting the umask for runc exec. (#3661)
• libct/cg: support SCHED_IDLE for runc cgroupfs. (#3377)
• checkpoint/restore: implement --manage-cgroups-mode=ignore. (#3546)
• seccomp: refactor flags support; add flags to features, set SPEC_ALLOW by
  default. (#3588)
• libct/cg/sd: use systemd v240+ new MAJOR:* syntax. (#3843)
• Support CFS bandwidth burst for CPU. (#3749, #3145)
• Support time namespaces. (#3876)
• Reduce the runc binary size by ~11% by updating
  github.com/checkpoint-restore/go-criu. (#3652)
• Add --pidfd-socket to runc run and runc exec to allow for management
  processes to receive a pidfd for the new process, allowing them to avoid pid
  reuse attacks. (#4045)

Deprecated

• runc option --criu is now ignored (with a warning), and the option will
  be removed entirely in a future release. Users who need a non-standard
  criu binary should rely on the standard way of looking up binaries in
  $PATH. (#3316)
• runc kill option -a is now deprecated. Previously, it had to be specified
  to kill a container (with SIGKILL) which does not have its own private PID
  namespace (so that runc would send SIGKILL to all processes). Now, this is
  done automatically. (#3864, #3825)
• github.com/opencontainers/runc/libcontainer/user is now deprecated, please
  use github.com/moby/sys/user instead. It will be removed in a future
  release. (#4017)

Changed

• When Intel RDT feature is not available, its initialization is skipped,
  resulting in slightly faster runc exec and runc run. (#3306)
• runc features is no longer experimental. (#3861)
• libcontainer users that create and kill containers from a daemon process
  (so that the container init is a child of that process) must now implement
  a proper child reaper in case a container does not have its own private PID
  namespace, as documented in container.Signal. (#3825)
• Sum anon and file from memory.stat for cgroupv2 root usage,
  as the root does not have memory.current for cgroupv2.
  This aligns cgroupv2 root usage more closely with cgroupv1 reporting.
  Additionally, report root swap usage as sum of swap and memory usage,
  aligned with v1 and existing non-root v2 reporting. (#3933)
• Add swapOnlyUsage in MemoryStats. This field reports swap-only usage.
  For cgroupv1, Usage and Failcnt are set by subtracting memory usage
  from memory+swap usage. For cgroupv2, Usage, Limit, and MaxUsage
  are set. (#4010)
• libcontainer users that create and kill containers from a daemon process
  (so that the container init is a child of that process) must now implement
  a proper child reaper in case a container does not have its own private PID
  namespace, as documented in container.Signal. (#3825)
• libcontainer: container.Signal no longer takes an all argument. Whether
  or not it is necessary to kill all processes in the container individually
  is now determined automatically. (#3825, #3885)
• seccomp: enable seccomp binary tree optimization. (#3405)
• runc run/runc exec: ignore SIGURG. (#3368)
• Remove tun/tap from the default device allowlist. (#3468)
• runc --root non-existent-dir list now reports an error for non-existent
  root directory. (#3374)

Fixed

• In case the runc binary resides on tmpfs, runc init no longer re-execs
  itself twice. (#3342)
• Our seccomp -ENOSYS stub now correctly handles multiplexed syscalls on
  s390 and s390x. This solves the issue where syscalls the host kernel did not
  support would return -EPERM despite the existence of the -ENOSYS stub
  code (this was due to how s390x does syscall multiplexing). (#3474)
• Remove tun/tap from the default device rules. (#3468)
• specconv: avoid mapping "acl" to MS_POSIXACL. (#3739)
• libcontainer: fix private PID namespace detection when killing the
  container. (#3866, #3825)
• systemd socket notification: fix race where runc exited before systemd
  properly handled the READY notification. (#3291, #3293)
• The -ENOSYS seccomp stub is now always generated for the native
  architecture that runc is running on. This is needed to work around some
  arguably specification-incompliant behaviour from Docker on architectures
  such as ppc64le, where the allowed architecture list is set to null. This
  ensures that we always generate at least one -ENOSYS stub for the native
  architecture even with these weird configs. (#4219)

Removed

• In order to fix performance issues in the "lightweight" bindfd protection
  against CVE-2019-5736, the temporary ro bind-mount of
  /proc/self/exe has been removed. runc now creates a binary copy in all
  cases. See the above notes about memfd-bind and runc-dmz as well as
  `contrib/cmd/memfd-bin...