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package devices
import (
"fmt"
"github.com/moby/sys/userns"
"golang.org/x/sys/unix"
"github.com/opencontainers/cgroups"
devices "github.com/opencontainers/cgroups/devices/config"
)
func isRWM(perms devices.Permissions) bool {
var r, w, m bool
for _, perm := range perms {
switch perm {
case 'r':
r = true
case 'w':
w = true
case 'm':
m = true
}
}
return r && w && m
}
// This is similar to the logic applied in crun for handling errors from bpf(2)
// <https://github.com/containers/crun/blob/0.17/src/libcrun/cgroup.c#L2438-L2470>.
func canSkipEBPFError(r *cgroups.Resources) bool {
// If we're running in a user namespace we can ignore eBPF rules because we
// usually cannot use bpf(2), as well as rootless containers usually don't
// have the necessary privileges to mknod(2) device inodes or access
// host-level instances (though ideally we would be blocking device access
// for rootless containers anyway).
if userns.RunningInUserNS() {
return true
}
// We cannot ignore an eBPF load error if any rule if is a block rule or it
// doesn't permit all access modes.
//
// NOTE: This will sometimes trigger in cases where access modes are split
// between different rules but to handle this correctly would require
// using ".../libcontainer/cgroup/devices".Emulator.
for _, dev := range r.Devices {
if !dev.Allow || !isRWM(dev.Permissions) {
return false
}
}
return true
}
func setV2(dirPath string, r *cgroups.Resources) error {
if r.SkipDevices {
return nil
}
insts, license, err := deviceFilter(r.Devices)
if err != nil {
return err
}
dirFD, err := unix.Open(dirPath, unix.O_DIRECTORY|unix.O_RDONLY, 0o600)
if err != nil {
return fmt.Errorf("cannot get dir FD for %s", dirPath)
}
defer unix.Close(dirFD)
if _, err := loadAttachCgroupDeviceFilter(insts, license, dirFD); err != nil {
if !canSkipEBPFError(r) {
return err
}
}
return nil
}
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