overlay: chown()ing the upper dir: ignore EINVAL on overflow IDs

When chown()ing the upper directory to match the lower directory, if the
ownership of the lower directory is the overflow UID:GID, ignore EINVAL.

Signed-off-by: Nalin Dahyabhai <[email protected]>

Author: nalind

pkg/overlay/overlay_linux.go

@@ -1,9 +1,11 @@
 package overlay
 
 import (
+	"errors"
 	"fmt"
 	"os"
 	"path/filepath"
+	"strconv"
 	"strings"
 	"syscall"
 
@@ -60,7 +62,22 @@ func MountWithOptions(contentDir, source, dest string, opts *Options) (mount spe
 			}
 			if stat, ok := st.Sys().(*syscall.Stat_t); ok {
 				if err := os.Chown(upperDir, int(stat.Uid), int(stat.Gid)); err != nil {
-					return mount, err
+					if !errors.Is(err, syscall.EINVAL) {
+						return mount, err
+					}
+					overflowed := false
+					overflowUIDText, uerr := os.ReadFile("/proc/sys/kernel/overflowuid")
+					overflowGIDText, gerr := os.ReadFile("/proc/sys/kernel/overflowgid")
+					if uerr == nil && gerr == nil {
+						overflowUID, uerr := strconv.Atoi(strings.TrimSpace(string(overflowUIDText)))
+						overflowGID, gerr := strconv.Atoi(strings.TrimSpace(string(overflowGIDText)))
+						if uerr == nil && gerr == nil && int(stat.Uid) == overflowUID && int(stat.Gid) == overflowGID {
+							overflowed = true
+						}
+					}
+					if !overflowed {
+						return mount, err
+					}
 				}
 				times := []syscall.Timespec{
 					stat.Atim,