mirror of
https://github.com/opencontainers/runc.git
synced 2026-07-11 06:03:57 +08:00
Kir Kolyshkin
3f65946756
A cgroup manager's Set method sets cgroup resources, but historically it was accepting configs.Cgroups. Refactor it to accept resources only. This is an improvement from the API point of view, as the method can not change cgroup configuration (such as path to the cgroup etc), it can only set (modify) its resources/limits. This also lays the foundation for complicated resource updates, as now Set has two sets of resources -- the one that was previously specified during cgroup manager creation (or the previous Set), and the one passed in the argument, so it could deduce the difference between these. This is a long term goal though. Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
91 lines
3.0 KiB
Go
91 lines
3.0 KiB
Go
// +build linux
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package fs2
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import (
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"github.com/opencontainers/runc/libcontainer/cgroups/ebpf"
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"github.com/opencontainers/runc/libcontainer/cgroups/ebpf/devicefilter"
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"github.com/opencontainers/runc/libcontainer/configs"
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"github.com/opencontainers/runc/libcontainer/devices"
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"github.com/opencontainers/runc/libcontainer/userns"
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"github.com/pkg/errors"
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"golang.org/x/sys/unix"
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)
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func isRWM(perms devices.Permissions) bool {
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var r, w, m bool
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for _, perm := range perms {
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switch perm {
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case 'r':
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r = true
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case 'w':
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w = true
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case 'm':
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m = true
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}
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}
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return r && w && m
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}
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// This is similar to the logic applied in crun for handling errors from bpf(2)
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// <https://github.com/containers/crun/blob/0.17/src/libcrun/cgroup.c#L2438-L2470>.
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func canSkipEBPFError(r *configs.Resources) bool {
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// If we're running in a user namespace we can ignore eBPF rules because we
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// usually cannot use bpf(2), as well as rootless containers usually don't
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// have the necessary privileges to mknod(2) device inodes or access
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// host-level instances (though ideally we would be blocking device access
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// for rootless containers anyway).
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if userns.RunningInUserNS() {
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return true
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}
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// We cannot ignore an eBPF load error if any rule if is a block rule or it
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// doesn't permit all access modes.
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//
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// NOTE: This will sometimes trigger in cases where access modes are split
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// between different rules but to handle this correctly would require
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// using ".../libcontainer/cgroup/devices".Emulator.
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for _, dev := range r.Devices {
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if !dev.Allow || !isRWM(dev.Permissions) {
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return false
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}
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}
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return true
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}
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func setDevices(dirPath string, r *configs.Resources) error {
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if r.SkipDevices {
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return nil
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}
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// XXX: This is currently a white-list (but all callers pass a blacklist of
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// devices). This is bad for a whole variety of reasons, but will need
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// to be fixed with co-ordinated effort with downstreams.
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insts, license, err := devicefilter.DeviceFilter(r.Devices)
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if err != nil {
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return err
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}
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dirFD, err := unix.Open(dirPath, unix.O_DIRECTORY|unix.O_RDONLY, 0600)
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if err != nil {
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return errors.Errorf("cannot get dir FD for %s", dirPath)
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}
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defer unix.Close(dirFD)
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// XXX: This code is currently incorrect when it comes to updating an
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// existing cgroup with new rules (new rulesets are just appended to
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// the program list because this uses BPF_F_ALLOW_MULTI). If we didn't
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// use BPF_F_ALLOW_MULTI we could actually atomically swap the
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// programs.
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//
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// The real issue is that BPF_F_ALLOW_MULTI makes it hard to have a
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// race-free blacklist because it acts as a whitelist by default, and
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// having a deny-everything program cannot be overridden by other
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// programs. You could temporarily insert a deny-everything program
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// but that would result in spurrious failures during updates.
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if _, err := ebpf.LoadAttachCgroupDeviceFilter(insts, license, dirFD); err != nil {
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if !canSkipEBPFError(r) {
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return err
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}
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}
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return nil
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}
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