*: kill one's own connection doesn't require SUPER privilege (#6954)

`kill tidb connID`, if the user is the owner of that connection, there
is no need to check the SUPER privilege.
SessionManager interface is slightly modified.

executor/executor_pkg_test.go

@@ -41,8 +41,12 @@ type mockSessionManager struct {
 }
 
 // ShowProcessList implements the SessionManager.ShowProcessList interface.
-func (msm *mockSessionManager) ShowProcessList() []util.ProcessInfo {
-	return msm.PS
+func (msm *mockSessionManager) ShowProcessList() map[uint64]util.ProcessInfo {
+	ret := make(map[uint64]util.ProcessInfo)
+	for _, item := range msm.PS {
+		ret[item.ID] = item
+	}
+	return ret
 }
 
 // Kill implements the SessionManager.Kill interface.

executor/show_test.go

@@ -417,8 +417,9 @@ type mockSessionManager struct {
 }
 
 // ShowProcessList implements the SessionManager.ShowProcessList interface.
-func (msm *mockSessionManager) ShowProcessList() []util.ProcessInfo {
-	return []util.ProcessInfo{msm.ShowProcess()}
+func (msm *mockSessionManager) ShowProcessList() map[uint64]util.ProcessInfo {
+	ps := msm.ShowProcess()
+	return map[uint64]util.ProcessInfo{ps.ID: ps}
 }
 
 // Kill implements the SessionManager.Kill interface.

plan/planbuilder.go

@@ -783,8 +783,21 @@ func (b *planBuilder) buildSimple(node ast.StmtNode) Plan {
 		b.visitInfo = appendVisitInfo(b.visitInfo, mysql.CreateUserPriv, "", "", "")
 	case *ast.GrantStmt:
 		b.visitInfo = collectVisitInfoFromGrantStmt(b.visitInfo, raw)
-	case *ast.SetPwdStmt, *ast.RevokeStmt, *ast.KillStmt:
+	case *ast.SetPwdStmt, *ast.RevokeStmt:
 		b.visitInfo = appendVisitInfo(b.visitInfo, mysql.SuperPriv, "", "", "")
+	case *ast.KillStmt:
+		// If you have the SUPER privilege, you can kill all threads and statements.
+		// Otherwise, you can kill only your own threads and statements.
+		sm := b.ctx.GetSessionManager()
+		if sm != nil {
+			processList := sm.ShowProcessList()
+			if pi, ok := processList[raw.ConnectionID]; ok {
+				loginUser := b.ctx.GetSessionVars().User
+				if pi.User != loginUser.Username {
+					b.visitInfo = appendVisitInfo(b.visitInfo, mysql.SuperPriv, "", "", "")
+				}
+			}
+		}
 	}
 	return p
 }

server/server.go

@@ -321,14 +321,15 @@ func (s *Server) onConn(c net.Conn) {
 }
 
 // ShowProcessList implements the SessionManager interface.
-func (s *Server) ShowProcessList() []util.ProcessInfo {
-	var rs []util.ProcessInfo
+func (s *Server) ShowProcessList() map[uint64]util.ProcessInfo {
 	s.rwlock.RLock()
+	rs := make(map[uint64]util.ProcessInfo, len(s.clients))
 	for _, client := range s.clients {
 		if atomic.LoadInt32(&client.status) == connStatusWaitShutdown {
 			continue
 		}
-		rs = append(rs, client.ctx.ShowProcess())
+		pi := client.ctx.ShowProcess()
+		rs[pi.ID] = pi
 	}
 	s.rwlock.RUnlock()
 	return rs

util/processinfo.go

@@ -33,6 +33,7 @@ type ProcessInfo struct {
 // SessionManager is an interface for session manage. Show processlist and
 // kill statement rely on this interface.
 type SessionManager interface {
-	ShowProcessList() []ProcessInfo
+	// ShowProcessList returns map[connectionID]ProcessInfo
+	ShowProcessList() map[uint64]ProcessInfo
 	Kill(connectionID uint64, query bool)
 }