From 9133caa6d3ad9abc4e21a3bbb719d4334efc6791 Mon Sep 17 00:00:00 2001
From: Bernerd Schaefer <bj.schaefer@gmail.com>
Date: Mon, 12 May 2014 14:41:07 +0200
Subject: [PATCH] Setup standard /dev symlinks

After copying allowed device nodes, set up "/dev/fd", "/dev/stdin",
"/dev/stdout", and "/dev/stderr" symlinks.

Docker-DCO-1.1-Signed-off-by: Bernerd Schaefer <bj.schaefer@gmail.com> (github: bernerdschaefer)
[rebased by @crosbymichael]
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
---
 libcontainer/mount/init.go | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/libcontainer/mount/init.go b/libcontainer/mount/init.go
index e5f2b43..6f3080c 100644
--- a/libcontainer/mount/init.go
+++ b/libcontainer/mount/init.go
@@ -54,6 +54,9 @@ func InitializeMountNamespace(rootfs, console string, container *libcontainer.Co
 	if err := SetupPtmx(rootfs, console, container.Context["mount_label"]); err != nil {
 		return err
 	}
+	if err := setupDevSymlinks(rootfs); err != nil {
+		return fmt.Errorf("dev symlinks %s", err)
+	}
 	if err := system.Chdir(rootfs); err != nil {
 		return fmt.Errorf("chdir into %s %s", rootfs, err)
 	}
@@ -114,6 +117,34 @@ func createIfNotExists(path string, isDir bool) error {
 	return nil
 }
 
+func setupDevSymlinks(rootfs string) error {
+	var links = [][2]string{
+		{"/proc/self/fd", "/dev/fd"},
+		{"/proc/self/fd/0", "/dev/stdin"},
+		{"/proc/self/fd/1", "/dev/stdout"},
+		{"/proc/self/fd/2", "/dev/stderr"},
+	}
+
+	// kcore support can be toggled with CONFIG_PROC_KCORE; only create a symlink
+	// in /dev if it exists in /proc.
+	if _, err := os.Stat("/proc/kcore"); err == nil {
+		links = append(links, [2]string{"/proc/kcore", "/dev/kcore"})
+	}
+
+	for _, link := range links {
+		var (
+			src = link[0]
+			dst = filepath.Join(rootfs, link[1])
+		)
+
+		if err := os.Symlink(src, dst); err != nil && !os.IsExist(err) {
+			return fmt.Errorf("symlink %s %s %s", src, dst, err)
+		}
+	}
+
+	return nil
+}
+
 func setupBindmounts(rootfs string, bindMounts libcontainer.Mounts) error {
 	for _, m := range bindMounts.OfType("bind") {
 		var (