never send procError after the socket closed

libcontainer/init_linux.go

@@ -107,7 +107,11 @@ func startInitialization() (retErr error) {
 
 	defer func() {
 		// If this defer is ever called, this means initialization has failed.
-		// Send the error back to the parent process in the form of an initError.
+		// Send the error back to the parent process in the form of an initError
+		// if the sync socket has not been closed.
+		if syncPipe.isClosed() {
+			return
+		}
 		ierr := initError{Message: retErr.Error()}
 		if err := writeSyncArg(syncPipe, procError, ierr); err != nil {
 			fmt.Fprintln(os.Stderr, err)

libcontainer/sync_unix.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"io"
 	"os"
+	"sync/atomic"
 
 	"golang.org/x/sys/unix"
 )
@@ -14,7 +15,8 @@ import (
 // which ends up making things like json.Decoder hang forever if the packet is
 // bigger than the internal read buffer.
 type syncSocket struct {
-	f *os.File
+	f      *os.File
+	closed atomic.Bool
 }
 
 func newSyncSocket(f *os.File) *syncSocket {
@@ -26,9 +28,15 @@ func (s *syncSocket) File() *os.File {
 }
 
 func (s *syncSocket) Close() error {
+	// Even with errors from Close(), we have to assume the pipe was closed.
+	s.closed.Store(true)
 	return s.f.Close()
 }
 
+func (s *syncSocket) isClosed() bool {
+	return s.closed.Load()
+}
+
 func (s *syncSocket) WritePacket(b []byte) (int, error) {
 	return s.f.Write(b)
 }

tests/integration/exec.bats

@@ -322,3 +322,21 @@ function check_exec_debug() {
 	runc exec --cgroup second test_busybox grep -w second /proc/self/cgroup
 	[ "$status" -eq 0 ]
 }
+
+@test "RUNC_DMZ=legacy runc exec [execve error]" {
+	cat <<EOF >rootfs/run.sh
+#!/mmnnttbb foo bar
+sh
+EOF
+	chmod +x rootfs/run.sh
+	RUNC_DMZ=legacy runc run -d --console-socket "$CONSOLE_SOCKET" test_busybox
+	RUNC_DMZ=legacy runc exec -t test_busybox /run.sh
+	[ "$status" -ne 0 ]
+
+	# After the sync socket closed, we should not send error to parent
+	# process, or else we will get a unnecessary error log(#4171).
+	# Although we never close the sync socket when doing exec,
+	# but we need to keep this test to ensure this behavior is always right.
+	[ ${#lines[@]} -eq 1 ]
+	[[ ${lines[0]} = *"exec failed: unable to start container process: exec /run.sh: no such file or directory"* ]]
+}

tests/integration/run.bats

@@ -247,3 +247,19 @@ EOF
 	[ "$status" -ne 0 ]
 	[[ "$output" = *"exec /run.sh: "* ]]
 }
+
+@test "RUNC_DMZ=legacy runc run [execve error]" {
+	cat <<EOF >rootfs/run.sh
+#!/mmnnttbb foo bar
+sh
+EOF
+	chmod +x rootfs/run.sh
+	update_config '.process.args = [ "/run.sh" ]'
+	RUNC_DMZ=legacy runc run test_hello
+	[ "$status" -ne 0 ]
+
+	# After the sync socket closed, we should not send error to parent
+	# process, or else we will get a unnecessary error log(#4171).
+	[ ${#lines[@]} -eq 1 ]
+	[[ ${lines[0]} = "exec /run.sh: no such file or directory" ]]
+}