bugfix: sort mounts according to the depth of destination path

daemon/mgr/spec_mount.go

@@ -4,6 +4,8 @@ import (
 	"context"
 	"fmt"
 	"os"
+	"path/filepath"
+	"sort"
 	"strconv"
 
 	"github.com/alibaba/pouch/apis/types"
@@ -108,7 +110,7 @@ func setupMounts(ctx context.Context, c *Container, s *specs.Spec) error {
 		mounts = append(mounts, generateNetworkMounts(c)...)
 	}
 
-	s.Mounts = mounts
+	s.Mounts = sortMounts(mounts)
 
 	if c.HostConfig.Privileged {
 		if !s.Root.Readonly {
@@ -175,3 +177,30 @@ func trySetupNetworkMount(mount *types.MountPoint, c *Container) bool {
 
 	return false
 }
+
+// mounts defines how to sort specs.Mount.
+type mounts []specs.Mount
+
+// Len returns the number of mounts.
+func (m mounts) Len() int {
+	return len(m)
+}
+
+// Less returns true if the destination of mount i < destination of mount j
+// in lexicographic order.
+func (m mounts) Less(i, j int) bool {
+	return filepath.Clean(m[i].Destination) < filepath.Clean(m[j].Destination)
+}
+
+// Swap swaps two items in an array of mounts.
+func (m mounts) Swap(i, j int) {
+	m[i], m[j] = m[j], m[i]
+}
+
+// sortMounts sorts an array of mounts in lexicographic order. This ensure that
+// the mount like /etc/resolv.conf will not mount before /etc, so /etc will
+// not shadow /etc/resolv.conf
+func sortMounts(m []specs.Mount) []specs.Mount {
+	sort.Stable(mounts(m))
+	return m
+}

daemon/mgr/spec_mount_test.go

@@ -0,0 +1,41 @@
+package mgr
+
+import (
+	"reflect"
+	"testing"
+
+	specs "github.com/opencontainers/runtime-spec/specs-go"
+)
+
+func Test_sortMounts(t *testing.T) {
+	tests := []struct {
+		name string
+		args []specs.Mount
+		want []specs.Mount
+	}{
+		{
+			"Mounts is nil case",
+			nil,
+			nil,
+		},
+		{
+			"Normal Mounts",
+			[]specs.Mount{
+				{Destination: "/etc/resolv.conf"},
+				{Destination: "/etc"},
+			},
+			[]specs.Mount{
+				{Destination: "/etc"},
+				{Destination: "/etc/resolv.conf"},
+			},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := sortMounts(tt.args)
+			if !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("sortMounts() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}