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test(unikontainers): add unit tests for mount and shared_fs utilities #815

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53548eb
refactor(unikontainers): make mount utilities mockable
Nachiket-Roy Jul 10, 2026
e4a4ea0
refactor(unikontainers): make shared_fs spawning mockable
Nachiket-Roy Jul 10, 2026
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57 changes: 35 additions & 22 deletions pkg/unikontainers/mount.go
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Original file line number Diff line number Diff line change
Expand Up @@ -33,6 +33,19 @@ import (

var ErrCopyDir = errors.New("can not copy a directory")

var (
mountSyscall = unix.Mount
mknodSyscall = unix.Mknod
statSyscall = unix.Stat
chmodSyscall = unix.Chmod
openSyscall = unix.Open
closeSyscall = unix.Close
chownSyscall = os.Chown
runningInUserNSHook = userns.RunningInUserNS
osChmodHook = os.Chmod
mkdirAllHook = os.MkdirAll
)

type mountFlagStruct struct {
clear bool
flag int
Expand All @@ -47,25 +60,25 @@ func createTmpfs(monRootfs string, path string, flags uint64, mode string, size
mountType := "tmpfs"
data := "mode=" + mode + ",size=" + size

err := os.MkdirAll(dstPath, 0755)
err := mkdirAllHook(dstPath, 0755)
if err != nil {
return fmt.Errorf("failed to create %s dir: %w", path, err)
}

err = unix.Mount(mountType, dstPath, mountType, uintptr(flags), data)
err = mountSyscall(mountType, dstPath, mountType, uintptr(flags), data)
if err != nil {
return fmt.Errorf("failed to mount %s tmpfs: %w", path, err)
}

// Remove propagation
err = unix.Mount("", dstPath, "", unix.MS_PRIVATE, "")
err = mountSyscall("", dstPath, "", unix.MS_PRIVATE, "")
if err != nil {
return fmt.Errorf("failed to create %s tmpfs: %w", path, err)
}

if mode == "1777" {
// sonarcloud:go:S2612 -- This is a tmpfs mount point, sticky bit 1777 is required (like /tmp), controlled path, safe by design
err := os.Chmod(dstPath, 01777) // NOSONAR
err := osChmodHook(dstPath, 01777) // NOSONAR
if err != nil {
return fmt.Errorf("failed to chmod %s: %w", path, err)
}
Expand All @@ -83,13 +96,13 @@ func createTmpfs(monRootfs string, path string, flags uint64, mode string, size
func setupDev(monRootfs string, devPath string) error {
// In a user namespace, always bind-mount the existing host device node.
// Only MS_BIND is used here (no extra flags) to mirror runc's device handling.
if userns.RunningInUserNS() {
if runningInUserNSHook() {
return fileFromHost(monRootfs, devPath, "", unix.MS_BIND, false)
}

// Get info of the original file
var devStat unix.Stat_t
err := unix.Stat(devPath, &devStat)
err := statSyscall(devPath, &devStat)
if err != nil {
return fmt.Errorf("failed to stat dev %s: %w", devPath, err)
}
Expand All @@ -116,14 +129,14 @@ func setupDev(monRootfs string, devPath string) error {
// the necessary directories
if filepath.Dir(devPath) != "/dev" {
dstDir := filepath.Dir(dstPath)
err = os.MkdirAll(dstDir, 0755)
err = mkdirAllHook(dstDir, 0755)
if err != nil {
return fmt.Errorf("failed to create directory %s: %w", dstDir, err)
}
}

// Create the new device node
err = unix.Mknod(dstPath, devStat.Mode, int(newDev)) //nolint: gosec
err = mknodSyscall(dstPath, devStat.Mode, int(newDev)) //nolint: gosec
if err != nil {
return fmt.Errorf("failed to make device node %s: %w", dstPath, err)
}
Expand All @@ -133,13 +146,13 @@ func setupDev(monRootfs string, devPath string) error {
// removes the burdain of getting kvm/block group id
permBits := devStat.Mode & 0o777
permBits |= 0o006
err = unix.Chmod(dstPath, permBits)
err = chmodSyscall(dstPath, permBits)
if err != nil {
return fmt.Errorf("failed to chmod %s: %w", dstPath, err)
}

// Set the owner as in the original file
err = os.Chown(dstPath, int(devStat.Uid), int(devStat.Gid))
err = chownSyscall(dstPath, int(devStat.Uid), int(devStat.Gid))
if err != nil {
return fmt.Errorf("failed to chown %s: %w", dstPath, err)
}
Expand All @@ -159,7 +172,7 @@ func setupDev(monRootfs string, devPath string) error {
func fileFromHost(monRootfs string, hostPath string, target string, mFlags int, withCopy bool) error {
// Get the info of the original file
var fileInfo unix.Stat_t
err := unix.Stat(hostPath, &fileInfo)
err := statSyscall(hostPath, &fileInfo)
if err != nil {
return err
}
Expand Down Expand Up @@ -200,12 +213,12 @@ func fileFromHost(monRootfs string, hostPath string, target string, mFlags int,
// If a copy is created, set up the permissions and ownership to match the original file.
// For bind mounts the host inode attributes remain unchanged.
if withCopy {
err = unix.Chmod(dstPath, fileInfo.Mode)
err = chmodSyscall(dstPath, fileInfo.Mode)
if err != nil {
return fmt.Errorf("failed to chmod %s: %w", dstPath, err)
}

err = os.Chown(dstPath, int(fileInfo.Uid), int(fileInfo.Gid))
err = chownSyscall(dstPath, int(fileInfo.Uid), int(fileInfo.Gid))
if err != nil {
return fmt.Errorf("failed to chown %s: %w", dstPath, err)
}
Expand All @@ -218,7 +231,7 @@ func fileFromHost(monRootfs string, hostPath string, target string, mFlags int,
// mount flags.
if mFlags & ^(unix.MS_BIND|unix.MS_REC|unix.MS_REMOUNT) != 0 {
flags := mFlags | unix.MS_BIND | unix.MS_REMOUNT
err = unix.Mount(dstPath, dstPath, "", uintptr(flags), "")
err = mountSyscall(dstPath, dstPath, "", uintptr(flags), "")
if err != nil {
return fmt.Errorf("failed to set mount flags for %s: %w", dstPath, err)
}
Expand All @@ -230,23 +243,23 @@ func fileFromHost(monRootfs string, hostPath string, target string, mFlags int,
// bindMountFile bind mounts a file/directory to a new path
func bindMountFile(hostPath string, dstDir string, dstPath string, perm uint32, mFlags int, isDir bool) error {
var mountTarget string
err := os.MkdirAll(dstDir, 0755)
err := mkdirAllHook(dstDir, 0755)
if err != nil {
return fmt.Errorf("failed to create directory %s: %w", dstDir, err)
}

if !isDir {
dstFile, err1 := unix.Open(dstPath, unix.O_CREAT, perm)
dstFile, err1 := openSyscall(dstPath, unix.O_CREAT, perm)
if err1 != nil {
return fmt.Errorf("failed to create file %s: %w", dstPath, err1)
}
unix.Close(dstFile)
closeSyscall(dstFile)
mountTarget = dstPath
} else {
mountTarget = dstDir
}

err = unix.Mount(hostPath, mountTarget, "", uintptr(mFlags), "")
err = mountSyscall(hostPath, mountTarget, "", uintptr(mFlags), "")
if err != nil {
return fmt.Errorf("failed to bind mount %s: %w", mountTarget, err)
}
Expand Down Expand Up @@ -288,7 +301,7 @@ func rootfsParentMountPrivate(path string) error {
// and EINVAL means this is not a mount point, so traverse up until we
// find one.
for {
err = unix.Mount("", path, "", unix.MS_PRIVATE, "")
err = mountSyscall("", path, "", unix.MS_PRIVATE, "")
if err == nil {
return nil
}
Expand All @@ -314,7 +327,7 @@ func prepareRoot(path string, rootfsPropagation string) error {
}
}

err := unix.Mount("", "/", "", uintptr(flag), "")
err := mountSyscall("", "/", "", uintptr(flag), "")
if err != nil {
return err
}
Expand All @@ -324,7 +337,7 @@ func prepareRoot(path string, rootfsPropagation string) error {
return err
}

return unix.Mount(path, path, "bind", unix.MS_BIND|unix.MS_REC, "")
return mountSyscall(path, path, "bind", unix.MS_BIND|unix.MS_REC, "")
}

func mountVolumes(rootfsPath string, mounts []specs.Mount) error {
Expand Down Expand Up @@ -366,7 +379,7 @@ func mountVolumes(rootfsPath string, mounts []specs.Mount) error {

dstPath := filepath.Join(rootfsPath, m.Destination)
for _, pFlag := range propFlag {
err = unix.Mount(dstPath, dstPath, "", uintptr(pFlag), "")
err = mountSyscall(dstPath, dstPath, "", uintptr(pFlag), "")
if err != nil {
return fmt.Errorf("failed to set propagation flag for %s: %w", m.Source, err)
}
Expand Down
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