pkg/osutil: introduce TempFile helper

Introduce TempFile helper and use it in several packages.

4 files changed, 34 insertions, 39 deletions

diff --git a/pkg/csource/build.go b/pkg/csource/build.go
index c0fc86078..cd67aa4f3 100644
--- a/pkg/csource/build.go
+++ b/pkg/csource/build.go
@@ -19,21 +19,19 @@ import (
 // Build builds a C/C++ program from source src and returns name of the resulting binary.
 // lang can be "c" or "c++".
 func Build(target *prog.Target, lang, src string) (string, error) {
-	// We call the binary syz-executor because it sometimes shows in bug titles,
-	// and we don't want 2 different bugs for when a crash is triggered during fuzzing and during repro.
-	bin, err := ioutil.TempFile("", "syz-executor")
-	if err != nil {
-		return "", fmt.Errorf("failed to create temp file: %v", err)
-	}
-	bin.Close()
 	sysTarget := targets.List[target.OS][target.Arch]
 	compiler := sysTarget.CCompilerPrefix + "gcc"
 	if _, err := exec.LookPath(compiler); err != nil {
 		return "", ErrNoCompiler
 	}
+	// We call the binary syz-executor because it sometimes shows in bug titles,
+	// and we don't want 2 different bugs for when a crash is triggered during fuzzing and during repro.
+	bin, err := osutil.TempFile("syz-executor")
+	if err != nil {
+		return "", err
+	}
 	flags := []string{
-		"-x", lang, "-Wall", "-Werror", "-O1", "-g", "-o", bin.Name(),
-		src, "-pthread",
+		"-x", lang, "-Wall", "-Werror", "-O1", "-g", "-o", bin, src, "-pthread",
 	}
 	flags = append(flags, sysTarget.CrossCFlags...)
 	if sysTarget.PtrSize == 4 {
@@ -46,12 +44,12 @@ func Build(target *prog.Target, lang, src string) (string, error) {
 		out, err = osutil.Command(compiler, flags...).CombinedOutput()
 	}
 	if err != nil {
-		os.Remove(bin.Name())
+		os.Remove(bin)
 		data, _ := ioutil.ReadFile(src)
 		return "", fmt.Errorf("failed to build program:\n%s\n%s\ncompiler invocation: %v %v",
 			data, out, compiler, flags)
 	}
-	return bin.Name(), nil
+	return bin, nil
 }
 
 var ErrNoCompiler = errors.New("no target compiler")
diff --git a/pkg/db/db_test.go b/pkg/db/db_test.go
index 538544c60..38456eb17 100644
--- a/pkg/db/db_test.go
+++ b/pkg/db/db_test.go
@@ -5,11 +5,12 @@ package db
 
 import (
 	"fmt"
-	"io/ioutil"
 	"math/rand"
 	"os"
 	"reflect"
 	"testing"
+
+	"github.com/google/syzkaller/pkg/osutil"
 )
 
 func TestBasic(t *testing.T) {
@@ -118,10 +119,9 @@ func TestLarge(t *testing.T) {
 }
 
 func tempFile(t *testing.T) string {
-	f, err := ioutil.TempFile("", "syzkaller.test.db")
+	fn, err := osutil.TempFile("syzkaller.test.db")
 	if err != nil {
-		t.Fatalf("failed to create temp file: %v", err)
+		t.Fatal(err)
 	}
-	f.Close()
-	return f.Name()
+	return fn
 }
diff --git a/pkg/osutil/osutil.go b/pkg/osutil/osutil.go
index 6f06fb4a4..a1d65e835 100644
--- a/pkg/osutil/osutil.go
+++ b/pkg/osutil/osutil.go
@@ -141,6 +141,17 @@ func WriteExecFile(filename string, data []byte) error {
 	return ioutil.WriteFile(filename, data, DefaultExecPerm)
 }
 
+// TempFile creates a unique temp filename.
+// Note: the file already exists when the function returns.
+func TempFile(prefix string) (string, error) {
+	f, err := ioutil.TempFile("", prefix)
+	if err != nil {
+		return "", fmt.Errorf("failed to create temp file: %v", err)
+	}
+	f.Close()
+	return f.Name(), nil
+}
+
 // Return all files in a directory.
 func ListDir(dir string) ([]string, error) {
 	f, err := os.Open(dir)
diff --git a/sys/syz-extract/fetch.go b/sys/syz-extract/fetch.go
index 47b6db8d3..db37fe4ab 100644
--- a/sys/syz-extract/fetch.go
+++ b/sys/syz-extract/fetch.go
@@ -6,7 +6,6 @@ package main
 import (
 	"bytes"
 	"fmt"
-	"io/ioutil"
 	"os"
 	"regexp"
 	"strconv"
@@ -98,39 +97,26 @@ type CompileData struct {
 }
 
 func compile(cc string, args []string, data *CompileData) (bin string, out []byte, err error) {
-	srcFile, err := ioutil.TempFile("", "")
-	if err != nil {
-		return "", nil, fmt.Errorf("failed to create temp file: %v", err)
-	}
-	srcFile.Close()
-	os.Remove(srcFile.Name())
-	srcName := srcFile.Name() + ".c"
-	defer os.Remove(srcName)
 	src := new(bytes.Buffer)
 	if err := srcTemplate.Execute(src, data); err != nil {
 		return "", nil, fmt.Errorf("failed to generate source: %v", err)
 	}
-	if err := ioutil.WriteFile(srcName, src.Bytes(), 0600); err != nil {
-		return "", nil, fmt.Errorf("failed to write source file: %v", err)
-	}
-
-	binFile, err := ioutil.TempFile("", "")
+	binFile, err := osutil.TempFile("syz-extract-bin")
 	if err != nil {
-		return "", nil, fmt.Errorf("failed to create temp file: %v", err)
+		return "", nil, err
 	}
-	binFile.Close()
-
 	args = append(args, []string{
-		srcName,
-		"-o", binFile.Name(),
+		"-x", "c", "-",
+		"-o", binFile,
 		"-w",
 	}...)
-	out, err = osutil.Command(cc, args...).CombinedOutput()
-	if err != nil {
-		os.Remove(binFile.Name())
+	cmd := osutil.Command(cc, args...)
+	cmd.Stdin = src
+	if out, err := cmd.CombinedOutput(); err != nil {
+		os.Remove(binFile)
 		return "", out, err
 	}
-	return binFile.Name(), nil, nil
+	return binFile, nil, nil
 }
 
 var srcTemplate = template.Must(template.New("").Parse(`