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Merged
AkihiroSuda merged 1 commit into from
Dec 31, 2019
Merged

Switch from mount(8) to mount(2) syscall #92

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34 changes: 14 additions & 20 deletions pkg/child/child.go
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Original file line number Diff line number Diff line change
Expand Up @@ -43,39 +43,33 @@ func mountSysfs() error {
return errors.Wrap(err, "creating a directory under /tmp")
}
defer os.RemoveAll(tmp)
cmds := [][]string{{"mount", "--rbind", "/sys/fs/cgroup", tmp}}
if err := common.Execs(os.Stderr, os.Environ(), cmds); err != nil {
return errors.Wrapf(err, "executing %v", cmds)
cgroupDir := "/sys/fs/cgroup"
if err := unix.Mount(cgroupDir, tmp, "", uintptr(unix.MS_BIND|unix.MS_REC), ""); err != nil {
return errors.Wrapf(err, "failed to create bind mount on %s", cgroupDir)
}
cmds = [][]string{{"mount", "-t", "sysfs", "none", "/sys"}}
if err := common.Execs(os.Stderr, os.Environ(), cmds); err != nil {

if err := unix.Mount("", "/sys", "sysfs", 0, ""); err != nil {
// when the sysfs in the parent namespace is RO,
// we can't mount RW sysfs even in the child namespace.
// https://github.com/rootless-containers/rootlesskit/pull/23#issuecomment-429292632
// https://github.com/torvalds/linux/blob/9f203e2f2f065cd74553e6474f0ae3675f39fb0f/fs/namespace.c#L3326-L3328
cmdsRo := [][]string{{"mount", "-t", "sysfs", "-o", "ro", "none", "/sys"}}
logrus.Warnf("failed to mount sysfs (%v), falling back to read-only mount (%v): %v",
cmds, cmdsRo, err)
if err := common.Execs(os.Stderr, os.Environ(), cmdsRo); err != nil {
logrus.Warnf("failed to mount sysfs, falling back to read-only mount: %v", err)
if err := unix.Mount("", "/sys", "sysfs", uintptr(unix.MS_RDONLY), ""); err != nil {
// when /sys/firmware is masked, even RO sysfs can't be mounted
logrus.Warnf("failed to mount sysfs (%v): %v", cmdsRo, err)
logrus.Warnf("failed to mount sysfs: %v", err)
}
}
cmds = [][]string{{"mount", "-n", "--move", tmp, "/sys/fs/cgroup"}}
if err := common.Execs(os.Stderr, os.Environ(), cmds); err != nil {
return errors.Wrapf(err, "executing %v", cmds)
if err := unix.Mount(tmp, cgroupDir, "", uintptr(unix.MS_MOVE), ""); err != nil {
return errors.Wrapf(err, "failed to move mount point from %s to %s", tmp, cgroupDir)
}
return nil
}

func mountProcfs() error {
cmds := [][]string{{"mount", "-t", "proc", "none", "/proc"}}
if err := common.Execs(os.Stderr, os.Environ(), cmds); err != nil {
cmdsRo := [][]string{{"mount", "-t", "proc", "-o", "ro", "none", "/proc"}}
logrus.Warnf("failed to mount procfs (%v), falling back to read-only mount (%v): %v",
cmds, cmdsRo, err)
if err := common.Execs(os.Stderr, os.Environ(), cmdsRo); err != nil {
logrus.Warnf("failed to mount procfs (%v): %v", cmdsRo, err)
if err := unix.Mount("", "/proc", "proc", 0, ""); err != nil {
logrus.Warnf("failed to mount procfs, falling back to read-only mount: %v", err)
if err := unix.Mount("", "/proc", "proc", uintptr(unix.MS_RDONLY), ""); err != nil {
logrus.Warnf("failed to mount procfs: %v", err)
}
}
return nil
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