diff --git a/libcontainer/rootfs_linux.go b/libcontainer/rootfs_linux.go index c302be086..ef764df5f 100644 --- a/libcontainer/rootfs_linux.go +++ b/libcontainer/rootfs_linux.go @@ -241,8 +241,8 @@ func prepareRootfs(pipe *syncSocket, iConfig *initConfig) (err error) { // to the current root ("/"), and not to the old rootfs before it becomes "/". Applying the // flag in prepareRoot would affect the host mount namespace if the container's // root mount is shared. - // MS_PRIVATE is skipped as rootfsParentMountPrivate() is already called. - if config.RootPropagation != 0 && config.RootPropagation&unix.MS_PRIVATE == 0 { + // MS_PRIVATE or MS_SLAVE is skipped as rootfsParentMountPropagation() is already called. + if config.RootPropagation != 0 && config.RootPropagation&(unix.MS_PRIVATE|unix.MS_SLAVE) == 0 { if err := mount("", "/", "", uintptr(config.RootPropagation), ""); err != nil { return fmt.Errorf("unable to apply root propagation flags: %w", err) } @@ -1061,19 +1061,27 @@ func mknodDevice(destDir *os.File, destName string, node *devices.Device) error return nil } -// rootfsParentMountPrivate ensures rootfs parent mount is private. +func rootfsParentMountPropagationFlags(rootPropagation int) uintptr { + if rootPropagation&unix.MS_SLAVE != 0 { + return unix.MS_SLAVE + } + return unix.MS_PRIVATE +} + +// rootfsParentMountPropagation ensures rootfs parent mount is not shared. // This is needed for two reasons: // - pivot_root() will fail if parent mount is shared; -// - when we bind mount rootfs, if its parent is not private, the new mount +// - when we bind mount rootfs, if its parent is (r)shared, the new mount // will propagate (leak!) to parent namespace and we don't want that. -func rootfsParentMountPrivate(path string) error { +func rootfsParentMountPropagation(path string, rootPropagation int) error { var err error + flags := rootfsParentMountPropagationFlags(rootPropagation) // Assuming path is absolute and clean (this is checked in // libcontainer/validate). Any error other than EINVAL means we failed, // 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 = unix.Mount("", path, "", flags, "") if err == nil { return nil } @@ -1083,9 +1091,9 @@ func rootfsParentMountPrivate(path string) error { path = filepath.Dir(path) } return &mountError{ - op: "remount-private", + op: "remount-propagation", target: path, - flags: unix.MS_PRIVATE, + flags: flags, err: err, } } @@ -1099,7 +1107,7 @@ func prepareRoot(config *configs.Config) error { return err } - if err := rootfsParentMountPrivate(config.Rootfs); err != nil { + if err := rootfsParentMountPropagation(config.Rootfs, config.RootPropagation); err != nil { return err }