Merge pull request #3954 from kinvolk/rata/idmap-tests

contrib/fs-idmap: Minor cleanups

Author: kolyshkin

contrib/cmd/fs-idmap/fs-idmap.go

@@ -2,7 +2,6 @@ package main
 
 import (
 	"fmt"
-	"log"
 	"os"
 	"os/exec"
 	"syscall"
@@ -11,40 +10,52 @@ import (
 )
 
 func main() {
-	if len(os.Args) < 2 {
-		log.Fatalf("usage: %s path_to_mount_set_attr", os.Args[0])
+	if len(os.Args) != 2 {
+		fmt.Fprintln(os.Stderr, "usage:", os.Args[0], "path_to_mount_set_attr")
+		os.Exit(1)
 	}
-
 	src := os.Args[1]
-	treeFD, err := unix.OpenTree(-1, src, uint(unix.OPEN_TREE_CLONE|unix.OPEN_TREE_CLOEXEC|unix.AT_EMPTY_PATH|unix.AT_RECURSIVE))
+	if err := supportsIDMap(src); err != nil {
+		fmt.Fprintln(os.Stderr, "fatal error:", err)
+		os.Exit(1)
+	}
+}
+
+func supportsIDMap(src string) error {
+	treeFD, err := unix.OpenTree(unix.AT_FDCWD, src, uint(unix.OPEN_TREE_CLONE|unix.OPEN_TREE_CLOEXEC|unix.AT_EMPTY_PATH))
 	if err != nil {
-		log.Fatalf("error calling open_tree %q: %v", src, err)
+		return fmt.Errorf("error calling open_tree %q: %w", src, err)
 	}
 	defer unix.Close(treeFD)
 
-	cmd := exec.Command("/usr/bin/sleep", "5")
+	cmd := exec.Command("sleep", "5")
 	cmd.SysProcAttr = &syscall.SysProcAttr{
 		Cloneflags:  syscall.CLONE_NEWUSER,
 		UidMappings: []syscall.SysProcIDMap{{ContainerID: 0, HostID: 65536, Size: 65536}},
 		GidMappings: []syscall.SysProcIDMap{{ContainerID: 0, HostID: 65536, Size: 65536}},
 	}
 	if err := cmd.Start(); err != nil {
-		log.Fatalf("failed to run the helper binary: %v", err)
+		return fmt.Errorf("failed to run the helper binary: %w", err)
 	}
+	defer func() {
+		_ = cmd.Process.Kill()
+		_ = cmd.Wait()
+	}()
 
 	path := fmt.Sprintf("/proc/%d/ns/user", cmd.Process.Pid)
 	var userNsFile *os.File
 	if userNsFile, err = os.Open(path); err != nil {
-		log.Fatalf("unable to get user ns file descriptor: %v", err)
-		return
+		return fmt.Errorf("unable to get user ns file descriptor: %w", err)
 	}
 	defer userNsFile.Close()
 
 	attr := unix.MountAttr{
 		Attr_set:  unix.MOUNT_ATTR_IDMAP,
 		Userns_fd: uint64(userNsFile.Fd()),
 	}
-	if err := unix.MountSetattr(treeFD, "", unix.AT_EMPTY_PATH|unix.AT_RECURSIVE, &attr); err != nil {
-		log.Fatalf("error calling mount_setattr: %v", err)
+	if err := unix.MountSetattr(treeFD, "", unix.AT_EMPTY_PATH, &attr); err != nil {
+		return fmt.Errorf("error calling mount_setattr: %w", err)
 	}
+
+	return nil
 }