use statUnix

Fixes #50102

Change-Id: I8ec67a56f2ab61d78ae5890e5a80cd2e8acd9a38

Author: qiulaidongfeng

src/archive/tar/common.go

@@ -612,7 +612,7 @@ func (fi headerFileInfo) String() string {
 }
 
 // sysStat, if non-nil, populates h from system-dependent fields of fi.
-var sysStat func(fi fs.FileInfo, h *Header) error
+var sysStat func(fi fs.FileInfo, h *Header, useFileInfoNames bool) error
 
 const (
 	// Mode constants from the USTAR spec:
@@ -715,7 +715,9 @@ func FileInfoHeader(fi fs.FileInfo, link string) (*Header, error) {
 			}
 		}
 	}
+	var useFileInfoNames = false
 	if iface, ok := fi.(FileInfoNames); ok {
+		useFileInfoNames = true
 		var err error
 		h.Gname, err = iface.Gname()
 		if err != nil {
@@ -733,10 +735,9 @@ func FileInfoHeader(fi fs.FileInfo, link string) (*Header, error) {
 		if err != nil {
 			return nil, err
 		}
-		return h, nil
 	}
 	if sysStat != nil {
-		return h, sysStat(fi, h)
+		return h, sysStat(fi, h, useFileInfoNames)
 	}
 	return h, nil
 }

src/archive/tar/stat_unix.go

@@ -23,28 +23,30 @@ func init() {
 // The downside is that renaming uname or gname by the OS never takes effect.
 var userMap, groupMap sync.Map // map[int]string
 
-func statUnix(fi fs.FileInfo, h *Header) error {
-	sys, ok := fi.Sys().(*syscall.Stat_t)
-	if !ok {
-		return nil
-	}
-	h.Uid = int(sys.Uid)
-	h.Gid = int(sys.Gid)
+func statUnix(fi fs.FileInfo, h *Header, useFileInfoNames bool) error {
+	if !useFileInfoNames {
+		sys, ok := fi.Sys().(*syscall.Stat_t)
+		if !ok {
+			return nil
+		}
+		h.Uid = int(sys.Uid)
+		h.Gid = int(sys.Gid)
 
-	// Best effort at populating Uname and Gname.
-	// The os/user functions may fail for any number of reasons
-	// (not implemented on that platform, cgo not enabled, etc).
-	if u, ok := userMap.Load(h.Uid); ok {
-		h.Uname = u.(string)
-	} else if u, err := user.LookupId(strconv.Itoa(h.Uid)); err == nil {
-		h.Uname = u.Username
-		userMap.Store(h.Uid, h.Uname)
-	}
-	if g, ok := groupMap.Load(h.Gid); ok {
-		h.Gname = g.(string)
-	} else if g, err := user.LookupGroupId(strconv.Itoa(h.Gid)); err == nil {
-		h.Gname = g.Name
-		groupMap.Store(h.Gid, h.Gname)
+		// Best effort at populating Uname and Gname.
+		// The os/user functions may fail for any number of reasons
+		// (not implemented on that platform, cgo not enabled, etc).
+		if u, ok := userMap.Load(h.Uid); ok {
+			h.Uname = u.(string)
+		} else if u, err := user.LookupId(strconv.Itoa(h.Uid)); err == nil {
+			h.Uname = u.Username
+			userMap.Store(h.Uid, h.Uname)
+		}
+		if g, ok := groupMap.Load(h.Gid); ok {
+			h.Gname = g.(string)
+		} else if g, err := user.LookupGroupId(strconv.Itoa(h.Gid)); err == nil {
+			h.Gname = g.Name
+			groupMap.Store(h.Gid, h.Gname)
+		}
 	}
 
 	h.AccessTime = statAtime(sys)