Set Setpgid on child git processes (#19865)

When Gitea is running as PID 1 git will occassionally orphan child processes leading
to (defunct) processes. This PR simply sets Setpgid to true on these child processes
meaning that these defunct processes will also be correctly reaped.

Fix #19077

Signed-off-by: Andrew Thornton <art27@cantab.net>

cmd/serv.go

@@ -24,6 +24,7 @@ import (
 	"code.gitea.io/gitea/modules/log"
 	"code.gitea.io/gitea/modules/pprof"
 	"code.gitea.io/gitea/modules/private"
+	"code.gitea.io/gitea/modules/process"
 	repo_module "code.gitea.io/gitea/modules/repository"
 	"code.gitea.io/gitea/modules/setting"
 	"code.gitea.io/gitea/services/lfs"
@@ -306,6 +307,7 @@ func runServ(c *cli.Context) error {
 		}
 	}
 
+	process.SetSysProcAttribute(gitcmd)
 	gitcmd.Dir = setting.RepoRootPath
 	gitcmd.Stdout = os.Stdout
 	gitcmd.Stdin = os.Stdin

modules/git/blame.go

@@ -124,6 +124,7 @@ func createBlameReader(ctx context.Context, dir string, command ...string) (*Bla
 	cmd := exec.CommandContext(ctx, command[0], command[1:]...)
 	cmd.Dir = dir
 	cmd.Stderr = os.Stderr
+	process.SetSysProcAttribute(cmd)
 
 	stdout, err := cmd.StdoutPipe()
 	if err != nil {

modules/git/command.go

@@ -157,6 +157,7 @@ func (c *Command) Run(opts *RunOpts) error {
 		"GIT_NO_REPLACE_OBJECTS=1",
 	)
 
+	process.SetSysProcAttribute(cmd)
 	cmd.Dir = opts.Dir
 	cmd.Stdout = opts.Stdout
 	cmd.Stderr = opts.Stderr

modules/markup/external/external.go

@@ -124,6 +124,8 @@ func (p *Renderer) Render(ctx *markup.RenderContext, input io.Reader, output io.
 		cmd.Stdin = input
 	}
 	cmd.Stdout = output
+	process.SetSysProcAttribute(cmd)
+
 	if err := cmd.Run(); err != nil {
 		return fmt.Errorf("%s render run command %s %v failed: %v", p.Name(), commands[0], args, err)
 	}

modules/process/manager_exec.go

@@ -58,6 +58,7 @@ func (pm *Manager) ExecDirEnvStdIn(ctx context.Context, timeout time.Duration, d
 	if stdIn != nil {
 		cmd.Stdin = stdIn
 	}
+	SetSysProcAttribute(cmd)
 
 	if err := cmd.Start(); err != nil {
 		return "", "", err

modules/process/manager_unix.go

@@ -0,0 +1,18 @@
+// Copyright 2022 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+//go:build !windows
+
+package process
+
+import (
+	"os/exec"
+	"syscall"
+)
+
+// SetSysProcAttribute sets the common SysProcAttrs for commands
+func SetSysProcAttribute(cmd *exec.Cmd) {
+	// When Gitea runs SubProcessA -> SubProcessB and SubProcessA gets killed by context timeout, use setpgid to make sure the sub processes can be reaped instead of leaving defunct(zombie) processes.
+	cmd.SysProcAttr = &syscall.SysProcAttr{Setpgid: true}
+}

modules/process/manager_windows.go

@@ -0,0 +1,16 @@
+// Copyright 2022 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+//go:build windows
+
+package process
+
+import (
+	"os/exec"
+)
+
+// SetSysProcAttribute sets the common SysProcAttrs for commands
+func SetSysProcAttribute(cmd *exec.Cmd) {
+	// Do nothing
+}

modules/ssh/ssh.go

@@ -102,6 +102,8 @@ func sessionHandler(session ssh.Session) {
 	}
 	defer stdin.Close()
 
+	process.SetSysProcAttribute(cmd)
+
 	wg := &sync.WaitGroup{}
 	wg.Add(2)
 

services/mailer/mailer.go

@@ -281,6 +281,7 @@ func (s *sendmailSender) Send(from string, to []string, msg io.WriterTo) error {
 	if err != nil {
 		return err
 	}
+	process.SetSysProcAttribute(cmd)
 
 	if err = cmd.Start(); err != nil {
 		_ = pipe.Close()