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Clears bits for mount flags incompatible with remount, Closes #6145 #6525

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Clears bits for mount flags incompatible with remount, Closes #6145 #6525

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12 changes: 7 additions & 5 deletions chroot/run_linux.go
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Original file line number Diff line number Diff line change
Expand Up @@ -88,6 +88,8 @@ var (
}
)

var makeFlags uintptr = uintptr(unix.MS_UNBINDABLE | unix.MS_PRIVATE | unix.MS_SLAVE | unix.MS_SHARED | unix.MS_REC)

func mountFlagNames(flags uintptr) []string {
var names []string
for flag, name := range mountFlagMap {
Expand Down Expand Up @@ -385,7 +387,7 @@ func makeReadOnly(mntpoint string, flags uintptr) error {
if fs.Flags&unix.ST_RDONLY == 0 {
// All callers currently pass MS_RDONLY in "flags", but in case they stop doing
// that at some point in the future...
if err := unix.Mount(mntpoint, mntpoint, "bind", flags|unix.MS_RDONLY|unix.MS_REMOUNT|unix.MS_BIND, ""); err != nil {
if err := unix.Mount(mntpoint, mntpoint, "bind", (flags|unix.MS_RDONLY|unix.MS_REMOUNT|unix.MS_BIND)&^makeFlags, ""); err != nil {
return fmt.Errorf("remounting %s in mount namespace read-only: %w", mntpoint, err)
}
}
Expand Down Expand Up @@ -440,7 +442,7 @@ func setupChrootBindMounts(spec *specs.Spec, bundlePath string) (undoBinds func(
return undoBinds, fmt.Errorf("checking if directory %q was bound read-only: %w", subDev, err)
}
if fs.Flags&unix.ST_RDONLY == 0 {
if err := unix.Mount(subDev, subDev, "bind", devFlags|unix.MS_REMOUNT|unix.MS_BIND, ""); err != nil {
if err := unix.Mount(subDev, subDev, "bind", (devFlags|unix.MS_REMOUNT|unix.MS_BIND)&^makeFlags, ""); err != nil {
return undoBinds, fmt.Errorf("remounting /dev in mount namespace read-only: %w", err)
}
}
Expand Down Expand Up @@ -642,7 +644,7 @@ func setupChrootBindMounts(spec *specs.Spec, bundlePath string) (undoBinds func(
if effectiveImportantFlags != expectedImportantFlags {
// Do a remount to try to get the desired flags to stick.
effectiveUnimportantFlags := uintptr(fs.Flags) & ^possibleImportantFlags
remountFlags := unix.MS_REMOUNT | bindFlags | requestFlags | mountFlagsForFSFlags(effectiveUnimportantFlags)
remountFlags := (unix.MS_REMOUNT | bindFlags | requestFlags | mountFlagsForFSFlags(effectiveUnimportantFlags)) &^ makeFlags
// If we are requesting a read-only mount, add any possibleImportantFlags present in fs.Flags to remountFlags.
if requestFlags&unix.ST_RDONLY == unix.ST_RDONLY {
remountFlags |= uintptr(fs.Flags) & possibleImportantFlags
Expand Down Expand Up @@ -701,7 +703,7 @@ func setupChrootBindMounts(spec *specs.Spec, bundlePath string) (undoBinds func(
return undoBinds, fmt.Errorf("checking if directory %q was bound read-only: %w", target, err)
}
if fs.Flags&unix.ST_RDONLY == 0 {
if err := unix.Mount(target, target, "", unix.MS_REMOUNT|unix.MS_RDONLY|bindFlags|mountFlagsForFSFlags(uintptr(fs.Flags)), ""); err != nil {
if err := unix.Mount(target, target, "", (unix.MS_REMOUNT|unix.MS_RDONLY|bindFlags|mountFlagsForFSFlags(uintptr(fs.Flags)))&^makeFlags, ""); err != nil {
return undoBinds, fmt.Errorf("remounting %q in mount namespace read-only: %w", target, err)
}
}
Expand Down Expand Up @@ -814,7 +816,7 @@ func setupChrootBindMounts(spec *specs.Spec, bundlePath string) (undoBinds func(
return undoBinds, fmt.Errorf("checking if masked directory %q was mounted read-only in mount namespace: %w", target, err)
}
if fs.Flags&unix.ST_RDONLY == 0 {
if err = unix.Mount(target, target, "", syscall.MS_REMOUNT|roFlags|mountFlagsForFSFlags(uintptr(fs.Flags)), ""); err != nil {
if err = unix.Mount(target, target, "", (syscall.MS_REMOUNT|roFlags|mountFlagsForFSFlags(uintptr(fs.Flags)))&^makeFlags, ""); err != nil {
return undoBinds, fmt.Errorf("making sure masked directory %q in mount namespace is read only: %w", target, err)
}
}
Expand Down