From e2970ea62d17ca98a3954c581523b8fa00a67bea Mon Sep 17 00:00:00 2001
From: Giuseppe Scrivano <gscrivan@redhat.com>
Date: Wed, 6 Feb 2019 15:29:33 +0100
Subject: rootless: do not override /dev/pts if not needed

when running in rootless mode we were unconditionally overriding
/dev/pts to take ride of gid=5.  This is not needed when multiple gids
are present in the namespace, which is always the case except when
running the tests suite with only one mapping.  So change it to check
how many gids are present before overriding the default mount.

Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>
---
 pkg/spec/spec.go | 34 +++++++++++++++++++++++++++-------
 1 file changed, 27 insertions(+), 7 deletions(-)

diff --git a/pkg/spec/spec.go b/pkg/spec/spec.go
index 46105af4a..76b8963ff 100644
--- a/pkg/spec/spec.go
+++ b/pkg/spec/spec.go
@@ -9,6 +9,7 @@ import (
 	"github.com/containers/storage/pkg/mount"
 	"github.com/docker/docker/daemon/caps"
 	"github.com/docker/go-units"
+	"github.com/opencontainers/runc/libcontainer/user"
 	spec "github.com/opencontainers/runtime-spec/specs-go"
 	"github.com/opencontainers/runtime-tools/generate"
 	"github.com/pkg/errors"
@@ -45,6 +46,18 @@ func supercedeUserMounts(mounts []spec.Mount, configMount []spec.Mount) []spec.M
 	return configMount
 }
 
+func getAvailableGids() (int64, error) {
+	idMap, err := user.ParseIDMapFile("/proc/self/gid_map")
+	if err != nil {
+		return 0, err
+	}
+	count := int64(0)
+	for _, r := range idMap {
+		count += r.Count
+	}
+	return count, nil
+}
+
 // CreateConfigToOCISpec parses information needed to create a container into an OCI runtime spec
 func CreateConfigToOCISpec(config *CreateConfig) (*spec.Spec, error) { //nolint
 	cgroupPerm := "ro"
@@ -91,14 +104,21 @@ func CreateConfigToOCISpec(config *CreateConfig) (*spec.Spec, error) { //nolint
 		g.AddMount(sysMnt)
 	}
 	if isRootless {
-		g.RemoveMount("/dev/pts")
-		devPts := spec.Mount{
-			Destination: "/dev/pts",
-			Type:        "devpts",
-			Source:      "devpts",
-			Options:     []string{"rprivate", "nosuid", "noexec", "newinstance", "ptmxmode=0666", "mode=0620"},
+		nGids, err := getAvailableGids()
+		if err != nil {
+			return nil, err
+		}
+		if nGids < 5 {
+			// If we have no GID mappings, the gid=5 default option would fail, so drop it.
+			g.RemoveMount("/dev/pts")
+			devPts := spec.Mount{
+				Destination: "/dev/pts",
+				Type:        "devpts",
+				Source:      "devpts",
+				Options:     []string{"rprivate", "nosuid", "noexec", "newinstance", "ptmxmode=0666", "mode=0620"},
+			}
+			g.AddMount(devPts)
 		}
-		g.AddMount(devPts)
 	}
 	if inUserNS && config.IpcMode.IsHost() {
 		g.RemoveMount("/dev/mqueue")
-- 
cgit v1.2.3-54-g00ecf