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Ignore isnotexist errors for restrict paths 

Handle the error when remounting certain files and paths as readonly if
they do not exist.
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@docker.com> (github: crosbymichael)
This commit is contained in:
Michael Crosby 2014-06-16 12:32:15 -07:00
parent 4145356abe
commit 874953d781
1 changed files with 5 additions and 2 deletions
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7
security/restrict/restrict.go
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@ -15,13 +15,14 @@ const defaultMountFlags = syscall.MS_NOEXEC | syscall.MS_NOSUID | syscall.MS_NOD
func mountReadonly(path string) error {
for i := 0; i < 5; i++ {
if err := system.Mount("", path, "", syscall.MS_REMOUNT|syscall.MS_RDONLY, ""); err != nil {
if err := system.Mount("", path, "", syscall.MS_REMOUNT|syscall.MS_RDONLY, ""); err != nil && !os.IsNotExist(err) {
switch err {
case syscall.EINVAL:
// Probably not a mountpoint, use bind-mount
if err := system.Mount(path, path, "", syscall.MS_BIND, ""); err != nil {
return err
}
return system.Mount(path, path, "", syscall.MS_BIND|syscall.MS_REMOUNT|syscall.MS_RDONLY|syscall.MS_REC|defaultMountFlags, "")
case syscall.EBUSY:
time.Sleep(100 * time.Millisecond)
@ -30,15 +31,16 @@ func mountReadonly(path string) error {
return err
}
}
return nil
}
return fmt.Errorf("unable to mount %s as readonly max retries reached", path)
}
// This has to be called while the container still has CAP_SYS_ADMIN (to be able to perform mounts).
// However, afterwards, CAP_SYS_ADMIN should be dropped (otherwise the user will be able to revert those changes).
func Restrict(mounts ...string) error {
// remount proc and sys as readonly
for _, dest := range mounts {
if err := mountReadonly(dest); err != nil {
return fmt.Errorf("unable to remount %s readonly: %s", dest, err)
@ -48,5 +50,6 @@ func Restrict(mounts ...string) error {
if err := system.Mount("/dev/null", "/proc/kcore", "", syscall.MS_BIND, ""); err != nil && !os.IsNotExist(err) {
return fmt.Errorf("unable to bind-mount /dev/null over /proc/kcore: %s", err)
}
return nil
}