src/os/pidfd_linux_test.go

// Copyright 2023 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package os_test

import (
	"errors"
	"internal/syscall/unix"
	"internal/testenv"
	"os"
	"os/exec"
	"syscall"
	"testing"
	"time"
)

func TestFindProcessViaPidfd(t *testing.T) {
	testenv.MustHaveGoBuild(t)
	t.Parallel()

	if err := os.CheckPidfdOnce(); err != nil {
		// Non-pidfd code paths tested in exec_unix_test.go.
		t.Skipf("skipping: pidfd not available: %v", err)
	}

	p, err := os.StartProcess(testenv.GoToolPath(t), []string{"go"}, &os.ProcAttr{})
	if err != nil {
		t.Fatalf("starting test process: %v", err)
	}
	p.Wait()

	// Use pid of a non-existing process.
	proc, err := os.FindProcess(p.Pid)
	// FindProcess should never return errors on Unix.
	if err != nil {
		t.Fatalf("FindProcess: got error %v, want <nil>", err)
	}
	// FindProcess should never return nil Process.
	if proc == nil {
		t.Fatal("FindProcess: got nil, want non-nil")
	}
	if proc.Status() != os.StatusDone {
		t.Fatalf("got process status: %v, want %d", proc.Status(), os.StatusDone)
	}

	// Check that all Process' public methods work as expected with
	// "done" Process.
	if err := proc.Kill(); err != os.ErrProcessDone {
		t.Errorf("Kill: got %v, want %v", err, os.ErrProcessDone)
	}
	if err := proc.Signal(os.Kill); err != os.ErrProcessDone {
		t.Errorf("Signal: got %v, want %v", err, os.ErrProcessDone)
	}
	if _, err := proc.Wait(); !errors.Is(err, syscall.ECHILD) {
		t.Errorf("Wait: got %v, want %v", err, os.ErrProcessDone)
	}
	// Release never returns errors on Unix.
	if err := proc.Release(); err != nil {
		t.Fatalf("Release: got %v, want <nil>", err)
	}
}

func TestStartProcessWithPidfd(t *testing.T) {
	testenv.MustHaveGoBuild(t)
	t.Parallel()

	if err := os.CheckPidfdOnce(); err != nil {
		// Non-pidfd code paths tested in exec_unix_test.go.
		t.Skipf("skipping: pidfd not available: %v", err)
	}

	var pidfd int
	p, err := os.StartProcess(testenv.GoToolPath(t), []string{"go"}, &os.ProcAttr{
		Sys: &syscall.SysProcAttr{
			PidFD: &pidfd,
		},
	})
	if err != nil {
		t.Fatalf("starting test process: %v", err)
	}
	defer syscall.Close(pidfd)

	if _, err := p.Wait(); err != nil {
		t.Fatalf("Wait: got %v, want <nil>", err)
	}

	// Check the pidfd is still valid
	err = unix.PidFDSendSignal(uintptr(pidfd), syscall.Signal(0))
	if !errors.Is(err, syscall.ESRCH) {
		t.Errorf("SendSignal: got %v, want %v", err, syscall.ESRCH)
	}
}

// Issue #69284
func TestPidfdLeak(t *testing.T) {
	exe := testenv.Executable(t)

	// Find the next 10 descriptors.
	// We need to get more than one descriptor in practice;
	// the pidfd winds up not being the next descriptor.
	const count = 10
	want := make([]int, count)
	for i := range count {
		var err error
		want[i], err = syscall.Open(exe, syscall.O_RDONLY, 0)
		if err != nil {
			t.Fatal(err)
		}
	}

	// Close the descriptors.
	for _, d := range want {
		syscall.Close(d)
	}

	// Start a process 10 times.
	for range 10 {
		// For testing purposes this has to be an absolute path.
		// Otherwise we will fail finding the executable
		// and won't start a process at all.
		cmd := exec.Command("/noSuchExecutable")
		cmd.Run()
	}

	// Open the next 10 descriptors again.
	got := make([]int, count)
	for i := range count {
		var err error
		got[i], err = syscall.Open(exe, syscall.O_RDONLY, 0)
		if err != nil {
			t.Fatal(err)
		}
	}

	// Close the descriptors
	for _, d := range got {
		syscall.Close(d)
	}

	t.Logf("got %v", got)
	t.Logf("want %v", want)

	// Allow some slack for runtime epoll descriptors and the like.
	if got[count-1] > want[count-1]+5 {
		t.Errorf("got descriptor %d, want %d", got[count-1], want[count-1])
	}
}

func TestProcessWithHandleLinux(t *testing.T) {
	t.Parallel()
	havePidfd := os.CheckPidfdOnce() == nil

	const envVar = "OSTEST_PROCESS_WITH_HANDLE"
	if os.Getenv(envVar) != "" {
		time.Sleep(1 * time.Minute)
		return
	}

	cmd := testenv.CommandContext(t, t.Context(), testenv.Executable(t), "-test.run=^"+t.Name()+"$")
	cmd = testenv.CleanCmdEnv(cmd)
	cmd.Env = append(cmd.Env, envVar+"=1")
	if err := cmd.Start(); err != nil {
		t.Fatal(err)
	}
	defer func() {
		cmd.Process.Kill()
		cmd.Wait()
	}()

	const sig = syscall.SIGINT
	called := false
	err := cmd.Process.WithHandle(func(pidfd uintptr) {
		called = true
		// Check the provided pidfd is valid, and terminate the child.
		err := unix.PidFDSendSignal(pidfd, sig)
		if err != nil {
			t.Errorf("PidFDSendSignal: got error %v, want nil", err)
		}
	})
	// If pidfd is not supported, WithHandle should fail.
	if !havePidfd && err == nil {
		t.Fatal("WithHandle: got nil, want error")
	}
	// If pidfd is supported, WithHandle should succeed.
	if havePidfd && err != nil {
		t.Fatalf("WithHandle: got error %v, want nil", err)
	}
	// If pidfd is supported, function should have been called, and vice versa.
	if havePidfd != called {
		t.Fatalf("WithHandle: havePidfd is %v, but called is %v", havePidfd, called)
	}
	// If pidfd is supported, wait on the child process to check it worked as intended.
	if called {
		err := cmd.Wait()
		if err == nil {
			t.Fatal("Wait: want error, got nil")
		}
		st := cmd.ProcessState.Sys().(syscall.WaitStatus)
		if !st.Signaled() {
			t.Fatal("ProcessState: want Signaled, got", err)
		}
		if gotSig := st.Signal(); sig != gotSig {
			t.Fatalf("ProcessState.Signal: want %v, got %v", sig, gotSig)
		}
		// Finally, check that WithHandle now returns ErrProcessDone.
		called = false
		err = cmd.Process.WithHandle(func(_ uintptr) {
			called = true
		})
		if err != os.ErrProcessDone {
			t.Fatalf("WithHandle: want os.ErrProcessDone, got %v", err)
		}
		if called {
			t.Fatal("called: want false, got true")
		}
	}
}