Fix hanging on runc create.

This reverts commit 0ab61ae, and also
* changes ReadStandardStreams to use ioutils.ReadFile;
* changes the uuid module used by the code (see commit abcb94d).

Using bytes.Buffer instead of plain os.File results in go runtime
creating two sets of pipes and spawning two threads (for stdout and
stderr) that copy the data from the pipe to the buffers.

It is not working when we execute runc create, because it spawns a child
(runc init) whose stdout and stderr are kept connected to the write ends
of the above pipes. As a result, those copying routines never finish,
and cmd.Run() never returns as it waits for those routines.

Therefore, let's go back to using temporary files. Note that the new
code is using ioutil.ReadAll instead of reusing the opened file
descriptors, which seems a bit cleaner.

Signed-off-by: Kir Kolyshkin <[email protected]>

Author: kolyshkin

validation/util/container.go

@@ -1,15 +1,16 @@
 package util
 
 import (
-	"bytes"
 	"encoding/json"
 	"errors"
 	"fmt"
+	"io/ioutil"
 	"os"
 	"os/exec"
 	"path/filepath"
 	"time"
 
+	"github.com/google/uuid"
 	rspecs "github.com/opencontainers/runtime-spec/specs-go"
 	"github.com/opencontainers/runtime-tools/generate"
 	"github.com/opencontainers/runtime-tools/specerror"
@@ -21,8 +22,8 @@ type Runtime struct {
 	BundleDir      string
 	PidFile        string
 	ID             string
-	stdout         bytes.Buffer
-	stderr         bytes.Buffer
+	stdout         *os.File
+	stderr         *os.File
 }
 
 // DefaultSignal represents the default signal sends to a container
@@ -78,18 +79,25 @@ func (r *Runtime) Create() (err error) {
 		args = append(args, r.ID)
 	}
 	cmd := exec.Command(r.RuntimeCommand, args...)
-	r.stdout.Reset()
-	cmd.Stdout = &r.stdout
-	r.stderr.Reset()
-	cmd.Stderr = &r.stderr
+	id := uuid.NewString()
+	r.stdout, err = os.OpenFile(filepath.Join(r.bundleDir(), fmt.Sprintf("stdout-%s", id)), os.O_CREATE|os.O_EXCL|os.O_RDWR, 0600)
+	if err != nil {
+		return err
+	}
+	cmd.Stdout = r.stdout
+	r.stderr, err = os.OpenFile(filepath.Join(r.bundleDir(), fmt.Sprintf("stderr-%s", id)), os.O_CREATE|os.O_EXCL|os.O_RDWR, 0600)
+	if err != nil {
+		return err
+	}
+	cmd.Stderr = r.stderr
 
 	err = cmd.Run()
 	if err == nil {
 		return err
 	}
 
 	if e, ok := err.(*exec.ExitError); ok {
-		stdout, stderr := r.StandardStreams()
+		stdout, stderr, _ := r.ReadStandardStreams()
 		if len(stderr) == 0 {
 			stderr = stdout
 		}
@@ -99,9 +107,14 @@ func (r *Runtime) Create() (err error) {
 	return err
 }
 
-// StandardStreams returns content from the stdout and stderr buffers.
-func (r *Runtime) StandardStreams() (stdout, stderr []byte) {
-	return r.stdout.Bytes(), r.stderr.Bytes()
+// ReadStandardStreams collects content from the stdout and stderr buffers.
+func (r *Runtime) ReadStandardStreams() (stdout []byte, stderr []byte, err error) {
+	stdout, err = ioutil.ReadFile(r.stdout.Name())
+	stderr, err2 := ioutil.ReadFile(r.stderr.Name())
+	if err == nil && err2 != nil {
+		err = err2
+	}
+	return
 }
 
 // Start a container

validation/util/test.go

@@ -228,7 +228,16 @@ func RuntimeInsideValidate(g *generate.Generator, t *tap.T, f PreFunc) (err erro
 		return err
 	}
 
-	stdout, stderr := r.StandardStreams()
+	stdout, stderr, err := r.ReadStandardStreams()
+	if err != nil {
+		if len(stderr) == 0 {
+			stderr = stdout
+		}
+		os.Stderr.WriteString("failed to read standard streams\n")
+		os.Stderr.Write(stderr)
+		return err
+	}
+
 	// Write stdout in the outter TAP
 	if t != nil {
 		diagnostic := map[string]string{