etcdclient: check mutex state in Unlock method of concurrency.Mutex

Check the values of myKey and myRev first in Unlock method to prevent calling Unlock without Lock. Because this may cause the value of pfx to be deleted by mistake.

Signed-off-by: chenyahui <cyhone@qq.com>

client/v3/concurrency/mutex.go

@@ -18,6 +18,7 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"strings"
 	"sync"
 
 	pb "go.etcd.io/etcd/api/v3/etcdserverpb"
@@ -27,6 +28,7 @@ import (
 // ErrLocked is returned by TryLock when Mutex is already locked by another session.
 var ErrLocked = errors.New("mutex: Locked by another session")
 var ErrSessionExpired = errors.New("mutex: session is expired")
+var ErrLockReleased = errors.New("mutex: lock has already been released")
 
 // Mutex implements the sync Locker interface with etcd
 type Mutex struct {
@@ -128,6 +130,14 @@ func (m *Mutex) tryAcquire(ctx context.Context) (*v3.TxnResponse, error) {
 }
 
 func (m *Mutex) Unlock(ctx context.Context) error {
+	if m.myKey == "" || m.myRev <= 0 || m.myKey == "\x00" {
+		return ErrLockReleased
+	}
+
+	if !strings.HasPrefix(m.myKey, m.pfx) {
+		return fmt.Errorf("invalid key %q, it should have prefix %q", m.myKey, m.pfx)
+	}
+
 	client := m.s.Client()
 	if _, err := client.Delete(ctx, m.myKey); err != nil {
 		return err

tests/integration/clientv3/concurrency/mutex_test.go

@@ -16,6 +16,7 @@ package concurrency_test
 
 import (
 	"context"
+	"errors"
 	"testing"
 
 	"go.etcd.io/etcd/client/v3"
@@ -70,3 +71,42 @@ func TestMutexLockSessionExpired(t *testing.T) {
 
 	<-m2Locked
 }
+
+func TestMutexUnlock(t *testing.T) {
+	cli, err := integration2.NewClient(t, clientv3.Config{Endpoints: exampleEndpoints()})
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer cli.Close()
+
+	s1, err := concurrency.NewSession(cli)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer s1.Close()
+
+	m1 := concurrency.NewMutex(s1, "/my-lock/")
+	err = m1.Unlock(context.TODO())
+	if err == nil {
+		t.Fatal("expect lock released error")
+	}
+	if !errors.Is(err, concurrency.ErrLockReleased) {
+		t.Fatal(err)
+	}
+
+	if err := m1.Lock(context.TODO()); err != nil {
+		t.Fatal(err)
+	}
+
+	if err := m1.Unlock(context.TODO()); err != nil {
+		t.Fatal(err)
+	}
+
+	err = m1.Unlock(context.TODO())
+	if err == nil {
+		t.Fatal("expect lock released error")
+	}
+	if !errors.Is(err, concurrency.ErrLockReleased) {
+		t.Fatal(err)
+	}
+}