Privileged containers can now restart if the host devices change

If a privileged container is running, stops, and the devices on the host
change, such as a USB device is unplugged, then a container would no
longer start. Previously, the devices from the host were only being
added to the container once: when the container was created. Now, this
happens every time the container starts.

I did this by adding a boolean to the container config that indicates
whether to mount all of the devices or not, which can be set via an option.

During spec generation, if the `MountAllDevices` option is set in the
container config, all host devices are added to the container.

Additionally, a couple of functions from `pkg/specgen/generate/config_linux.go`
were moved into `pkg/util/utils_linux.go` as they were needed in
multiple packages.

Closes #13899

Signed-off-by: Jake Correnti <jcorrenti13@gmail.com>

pkg/util/utils_linux.go

@@ -3,13 +3,24 @@ package util
 import (
 	"fmt"
 	"io/fs"
+	"io/ioutil"
 	"os"
 	"path/filepath"
+	"strings"
 	"syscall"
 
+	"github.com/containers/podman/v4/libpod/define"
+	"github.com/containers/podman/v4/pkg/rootless"
 	"github.com/containers/psgo"
+	spec "github.com/opencontainers/runtime-spec/specs-go"
+	"github.com/opencontainers/runtime-tools/generate"
 	"github.com/pkg/errors"
 	"github.com/sirupsen/logrus"
+	"golang.org/x/sys/unix"
+)
+
+var (
+	errNotADevice = errors.New("not a device node")
 )
 
 // GetContainerPidInformationDescriptors returns a string slice of all supported
@@ -59,3 +70,134 @@ func FindDeviceNodes() (map[string]string, error) {
 
 	return nodes, nil
 }
+
+func AddPrivilegedDevices(g *generate.Generator) error {
+	hostDevices, err := getDevices("/dev")
+	if err != nil {
+		return err
+	}
+	g.ClearLinuxDevices()
+
+	if rootless.IsRootless() {
+		mounts := make(map[string]interface{})
+		for _, m := range g.Mounts() {
+			mounts[m.Destination] = true
+		}
+		newMounts := []spec.Mount{}
+		for _, d := range hostDevices {
+			devMnt := spec.Mount{
+				Destination: d.Path,
+				Type:        define.TypeBind,
+				Source:      d.Path,
+				Options:     []string{"slave", "nosuid", "noexec", "rw", "rbind"},
+			}
+			if d.Path == "/dev/ptmx" || strings.HasPrefix(d.Path, "/dev/tty") {
+				continue
+			}
+			if _, found := mounts[d.Path]; found {
+				continue
+			}
+			newMounts = append(newMounts, devMnt)
+		}
+		g.Config.Mounts = append(newMounts, g.Config.Mounts...)
+		if g.Config.Linux.Resources != nil {
+			g.Config.Linux.Resources.Devices = nil
+		}
+	} else {
+		for _, d := range hostDevices {
+			g.AddDevice(d)
+		}
+		// Add resources device - need to clear the existing one first.
+		if g.Config.Linux.Resources != nil {
+			g.Config.Linux.Resources.Devices = nil
+		}
+		g.AddLinuxResourcesDevice(true, "", nil, nil, "rwm")
+	}
+
+	return nil
+}
+
+// based on getDevices from runc (libcontainer/devices/devices.go)
+func getDevices(path string) ([]spec.LinuxDevice, error) {
+	files, err := ioutil.ReadDir(path)
+	if err != nil {
+		if rootless.IsRootless() && os.IsPermission(err) {
+			return nil, nil
+		}
+		return nil, err
+	}
+	out := []spec.LinuxDevice{}
+	for _, f := range files {
+		switch {
+		case f.IsDir():
+			switch f.Name() {
+			// ".lxc" & ".lxd-mounts" added to address https://github.com/lxc/lxd/issues/2825
+			case "pts", "shm", "fd", "mqueue", ".lxc", ".lxd-mounts":
+				continue
+			default:
+				sub, err := getDevices(filepath.Join(path, f.Name()))
+				if err != nil {
+					return nil, err
+				}
+				if sub != nil {
+					out = append(out, sub...)
+				}
+				continue
+			}
+		case f.Name() == "console":
+			continue
+		case f.Mode()&os.ModeSymlink != 0:
+			continue
+		}
+
+		device, err := DeviceFromPath(filepath.Join(path, f.Name()))
+		if err != nil {
+			if err == errNotADevice {
+				continue
+			}
+			if os.IsNotExist(err) {
+				continue
+			}
+			return nil, err
+		}
+		out = append(out, *device)
+	}
+	return out, nil
+}
+
+// Copied from github.com/opencontainers/runc/libcontainer/devices
+// Given the path to a device look up the information about a linux device
+func DeviceFromPath(path string) (*spec.LinuxDevice, error) {
+	var stat unix.Stat_t
+	err := unix.Lstat(path, &stat)
+	if err != nil {
+		return nil, err
+	}
+	var (
+		devType   string
+		mode      = stat.Mode
+		devNumber = uint64(stat.Rdev) // nolint: unconvert
+		m         = os.FileMode(mode)
+	)
+
+	switch {
+	case mode&unix.S_IFBLK == unix.S_IFBLK:
+		devType = "b"
+	case mode&unix.S_IFCHR == unix.S_IFCHR:
+		devType = "c"
+	case mode&unix.S_IFIFO == unix.S_IFIFO:
+		devType = "p"
+	default:
+		return nil, errNotADevice
+	}
+
+	return &spec.LinuxDevice{
+		Type:     devType,
+		Path:     path,
+		FileMode: &m,
+		UID:      &stat.Uid,
+		GID:      &stat.Gid,
+		Major:    int64(unix.Major(devNumber)),
+		Minor:    int64(unix.Minor(devNumber)),
+	}, nil
+}