test access stdio in userns container

Signed-off-by: lifubang <[email protected]>

tests/integration/userns.bats

@@ -36,6 +36,26 @@ function teardown() {
 	fi
 }
 
+@test "runc check stdio permission in userns [terminal=false]" {
+	update_config ' (.. | select(.terminal? != null)) .terminal |= false
+			| (.. | select(.[]? == "sh")) += ["-c", "echo errormsg > /dev/stderr"]'
+
+	touch log
+	__runc create test_busybox >log 2>&1
+
+	runc start test_busybox
+	[ "$status" -eq 0 ]
+
+	out=$(cat log)
+	# Keep this to debug is useful once we have a regression about this.
+	echo "$out" >&2
+
+	# We should let stdio could be accessed in user ns container.
+	# Please see https://github.com/opencontainers/runc/issues/4475
+	# We should not get error: touch: /dev/stderr: Permission denied.
+	[[ "$out" = "errormsg" ]]
+}
+
 @test "userns with simple mount" {
 	update_config ' .process.args += ["-c", "stat /tmp/mount-1/foo.txt"]
 		| .mounts += [{"source": "source-accessible/dir", "destination": "/tmp/mount-1", "options": ["bind"]}] '