From bc0de86b495ae014b209431ed7cb90fc3d5e4d1f Mon Sep 17 00:00:00 2001
From: Kir Kolyshkin <kolyshkin@gmail.com>
Date: Mon, 9 Apr 2018 15:58:40 -0700
Subject: [PATCH] archive/tar: do not populate user/group names

This reverts part of commit 29a18899379c ("archive/tar: populate
uname/gname/devmajor/devminor in FileInfoHeader"). The reason is
using os/user functions to resolved uids/gids to names breaks
the static build for Linux/glibc case (the resulting binary panics
on NULL pointer dereference).

For much more details, see https://github.com/golang/go/issues/23265

This is ultimately fixed in Go 1.11 (provided that "osusergo" build tag
is set (see https://github.com/golang/go/commit/62f0127d81). In the
meantime, let's use this fork.

Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
---
 src/archive/tar/stat_unix.go | 26 +++-----------------------
 1 file changed, 3 insertions(+), 23 deletions(-)

diff --git a/src/archive/tar/stat_unix.go b/src/archive/tar/stat_unix.go
index 868105f338..9640ed4bab 100644
--- a/src/archive/tar/stat_unix.go
+++ b/src/archive/tar/stat_unix.go
@@ -8,10 +8,7 @@ package tar
 
 import (
 	"os"
-	"os/user"
 	"runtime"
-	"strconv"
-	"sync"
 	"syscall"
 )
 
@@ -19,10 +16,6 @@ func init() {
 	sysStat = statUnix
 }
 
-// userMap and groupMap caches UID and GID lookups for performance reasons.
-// 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 os.FileInfo, h *Header) error {
 	sys, ok := fi.Sys().(*syscall.Stat_t)
 	if !ok {
@@ -31,22 +24,9 @@ func statUnix(fi os.FileInfo, h *Header) error {
 	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)
-	}
-
+	// TODO(bradfitz): populate username & group.  os/user
+	// doesn't cache LookupId lookups, and lacks group
+	// lookup functions.
 	h.AccessTime = statAtime(sys)
 	h.ChangeTime = statCtime(sys)
 

base-commit: 4af1337d1e9eb9e7b766c9deb787c78413bb25c4
-- 
2.24.1