Use fifo close to prevent leak of top level directory (#752)

Previously the vm agent did clean of fifos by removing each fifo;
however, this resulted in a leak of the top level directory of the fifos
until the task was deleted. For long running tasks, this resulted in
4096 byte leak on the microvm filesystem until the task was deleted.

Signed-off-by: Austin Vazquez <[email protected]>

Author: austinvazquez

agent/service.go

@@ -253,6 +253,9 @@ func (ts *TaskService) Create(requestCtx context.Context, req *taskAPI.CreateTas
 			logger.WithError(err).Error()
 			return nil, err
 		}
+		ts.addCleanup(taskExecID, func() error {
+			return fifoSet.Close()
+		})
 
 		var stdinConnectorPair *vm.IOConnectorPair
 		if req.Stdin != "" {
@@ -520,6 +523,9 @@ func (ts *TaskService) Exec(requestCtx context.Context, req *taskAPI.ExecProcess
 			logger.WithError(err).Error()
 			return nil, err
 		}
+		ts.addCleanup(taskExecID, func() error {
+			return fifoSet.Close()
+		})
 
 		var stdinConnectorPair *vm.IOConnectorPair
 		if req.Stdin != "" {
@@ -528,9 +534,6 @@ func (ts *TaskService) Exec(requestCtx context.Context, req *taskAPI.ExecProcess
 				ReadConnector:  vm.VSockAcceptConnector(extraData.StdinPort),
 				WriteConnector: vm.WriteFIFOConnector(fifoSet.Stdin),
 			}
-			ts.addCleanup(taskExecID, func() error {
-				return os.RemoveAll(req.Stdin)
-			})
 		}
 
 		var stdoutConnectorPair *vm.IOConnectorPair
@@ -540,9 +543,6 @@ func (ts *TaskService) Exec(requestCtx context.Context, req *taskAPI.ExecProcess
 				ReadConnector:  vm.ReadFIFOConnector(fifoSet.Stdout),
 				WriteConnector: vm.VSockAcceptConnector(extraData.StdoutPort),
 			}
-			ts.addCleanup(taskExecID, func() error {
-				return os.RemoveAll(req.Stdout)
-			})
 		}
 
 		var stderrConnectorPair *vm.IOConnectorPair
@@ -552,9 +552,6 @@ func (ts *TaskService) Exec(requestCtx context.Context, req *taskAPI.ExecProcess
 				ReadConnector:  vm.ReadFIFOConnector(fifoSet.Stderr),
 				WriteConnector: vm.VSockAcceptConnector(extraData.StderrPort),
 			}
-			ts.addCleanup(taskExecID, func() error {
-				return os.RemoveAll(req.Stderr)
-			})
 		}
 
 		ioConnectorSet = vm.NewIOConnectorProxy(stdinConnectorPair, stdoutConnectorPair, stderrConnectorPair)