From d9d2fecdf47d6ac48e08d57f0a2b825331b43e18 Mon Sep 17 00:00:00 2001
From: Spike Curtis <spike@coder.com>
Date: Thu, 18 Jan 2024 16:05:52 +0400
Subject: [PATCH] fix: use raw syscalls to write binary we execute

---
 provisioner/terraform/executor.go       |  8 ++++++++
 provisioner/terraform/provision_test.go | 13 ++++++++++++-
 2 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/provisioner/terraform/executor.go b/provisioner/terraform/executor.go
index 3917e4ca154fd..0a6c1df943595 100644
--- a/provisioner/terraform/executor.go
+++ b/provisioner/terraform/executor.go
@@ -123,6 +123,10 @@ func (e *executor) execParseJSON(ctx, killCtx context.Context, args, env []strin
 	cmd.Stdout = out
 	cmd.Stderr = stdErr
 
+	e.server.logger.Debug(ctx, "executing terraform command with JSON result",
+		slog.F("binary_path", e.binaryPath),
+		slog.F("args", args),
+	)
 	err := cmd.Start()
 	if err != nil {
 		return err
@@ -348,6 +352,10 @@ func (e *executor) graph(ctx, killCtx context.Context) (string, error) {
 	cmd.Dir = e.workdir
 	cmd.Env = e.basicEnv()
 
+	e.server.logger.Debug(ctx, "executing terraform command graph",
+		slog.F("binary_path", e.binaryPath),
+		slog.F("args", "graph"),
+	)
 	err := cmd.Start()
 	if err != nil {
 		return "", err
diff --git a/provisioner/terraform/provision_test.go b/provisioner/terraform/provision_test.go
index 4c2187ced7bb4..85868fe6112df 100644
--- a/provisioner/terraform/provision_test.go
+++ b/provisioner/terraform/provision_test.go
@@ -14,6 +14,7 @@ import (
 	"runtime"
 	"sort"
 	"strings"
+	"syscall"
 	"testing"
 	"time"
 
@@ -165,8 +166,18 @@ func TestProvision_Cancel(t *testing.T) {
 
 			// Example: exec /path/to/terrafork_fake_cancel.sh 1.2.1 apply "$@"
 			content := fmt.Sprintf("#!/bin/sh\nexec %q %s %s \"$@\"\n", fakeBin, terraform.TerraformVersion.String(), tt.mode)
-			err := os.WriteFile(binPath, []byte(content), 0o755) //#nosec
+
+			// golang's standard OS library can sometimes leave the file descriptor open even after
+			// "Closing" the file (which can then lead to a "text file busy" error, so we bypass this
+			// and use syscall directly).
+			fd, err := syscall.Open(binPath, syscall.O_WRONLY|syscall.O_CREAT, 0o755)
+			require.NoError(t, err)
+			n, err := syscall.Write(fd, []byte(content))
+			require.NoError(t, err)
+			require.Equal(t, len(content), n)
+			err = syscall.Close(fd)
 			require.NoError(t, err)
+			t.Logf("wrote fake terraform script to %s", binPath)
 
 			ctx, api := setupProvisioner(t, &provisionerServeOptions{
 				binaryPath: binPath,