Bump oc/cgroups to v0.1.0, improve sub-cgroup checks - #5403
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Because of opencontainers/cgroups#69 I want to backport this to at least 1.5 but maybe also 1.4. I mean, a buffer overrun from the kernel is no joke. |
This was referenced Aug 17, 2026
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See https://github.com/opencontainers/cgroups/releases/tag/v0.1.0 Notably, it no longer uses the high-level cilium/ebpf API (btf, link, and the ELF loader) to manage cgroup v2 device rules, which makes the runc binary about 1 MiB (7.5%) smaller on amd64, removes ~20K lines of vendored code, and drops five transitive dependencies (josharian/native, jsimonetti/rtnetlink, mdlayher/netlink, mdlayher/socket, golang.org/x/sync). Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
The check that a sub-cgroup path (as set by runc exec --cgroup, or libcontainer's Process.SubCgroupPaths) does not escape the container's cgroup was too lax: a plain prefix check also accepts a sibling cgroup whose name starts with the container cgroup name (say, "../foo-suffix" for a container cgroup named "foo"). For addIntoCgroupV1 (used for per-controller sub-cgroup paths, which AddPid does not support) the resulting path is passed to WriteCgroupProc as is, so the pid did end up in the sibling cgroup. For prepareCgroupFD the subsequent cgroups.OpenFile call cleans the path, so nothing escaped in practice, but the check was wrong nevertheless. Use the same check as opencontainers/cgroups v0.0.9 does in AddPid, and add test cases for both code paths. Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com> Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
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For oc/cgroups release notes, see
Notably, v0.1.0 no longer uses the high-level cilium/ebpf API (
btf,link,and the ELF loader) to manage cgroup v2 device rules. For runc, this means:
a
seccomp libpathrsbuild with go1.26.5 on amd64;jsimonetti/rtnetlink, mdlayher/netlink, mdlayher/socket, and
golang.org/x/sync;
This PR also improves the
runc exec --cgroupsub-cgroup path check (see thesecond commit).