diff --git a/libcontainer/rootfs_linux.go b/libcontainer/rootfs_linux.go index 89ce38e8d48..aa061ab0817 100644 --- a/libcontainer/rootfs_linux.go +++ b/libcontainer/rootfs_linux.go @@ -18,6 +18,7 @@ import ( "github.com/opencontainers/runc/libcontainer/cgroups" "github.com/opencontainers/runc/libcontainer/configs" "github.com/opencontainers/runc/libcontainer/label" + "github.com/opencontainers/runc/libcontainer/system" ) const defaultMountFlags = syscall.MS_NOEXEC | syscall.MS_NOSUID | syscall.MS_NODEV @@ -383,11 +384,12 @@ func reOpenDevNull() error { // Create the device nodes in the container. func createDevices(config *configs.Config) error { + useBindMount := system.RunningInUserNS() || config.Namespaces.Contains(configs.NEWUSER) oldMask := syscall.Umask(0000) for _, node := range config.Devices { // containers running in a user namespace are not allowed to mknod // devices so we can just bind mount it from the host. - if err := createDeviceNode(config.Rootfs, node, config.Namespaces.Contains(configs.NEWUSER)); err != nil { + if err := createDeviceNode(config.Rootfs, node, useBindMount); err != nil { syscall.Umask(oldMask) return err } diff --git a/libcontainer/system/linux.go b/libcontainer/system/linux.go index 2cc3ef803a3..6c835e68ec2 100644 --- a/libcontainer/system/linux.go +++ b/libcontainer/system/linux.go @@ -3,6 +3,9 @@ package system import ( + "bufio" + "fmt" + "os" "os/exec" "syscall" "unsafe" @@ -75,3 +78,37 @@ func Setctty() error { } return nil } + +/* + * Detect whether we are currently running in a user namespace. + * Copied from github.com/lxc/lxd/shared/util.go + */ +func RunningInUserNS() bool { + file, err := os.Open("/proc/self/uid_map") + if err != nil { + /* + * This kernel-provided file only exists if user namespaces are + * supported + */ + return false + } + defer file.Close() + + buf := bufio.NewReader(file) + l, _, err := buf.ReadLine() + if err != nil { + return false + } + + line := string(l) + var a, b, c int64 + fmt.Sscanf(line, "%d %d %d", &a, &b, &c) + /* + * We assume we are in the initial user namespace if we have a full + * range - 4294967295 uids starting at uid 0. + */ + if a == 0 && b == 0 && c == 4294967295 { + return false + } + return true +}