runc exec: fail with exit code of 255

exec.go

@@ -101,7 +101,8 @@ following will output a list of processes running in the container:
 		if err == nil {
 			os.Exit(status)
 		}
-		return fmt.Errorf("exec failed: %w", err)
+		fatalWithCode(fmt.Errorf("exec failed: %w", err), 255)
+		return nil // to satisfy the linter
 	},
 	SkipArgReorder: true,
 }

man/runc-exec.8.md

@@ -59,6 +59,11 @@ multiple times.
 : Pass _N_ additional file descriptors to the container (**stdio** +
 **$LISTEN_FDS** + _N_ in total). Default is **0**.
 
+# EXIT STATUS
+
+Exits with a status of _command_ (unless **-d** is used), or **255** if
+an error occurred.
+
 # EXAMPLES
 If the container can run **ps**(1) command, the following
 will output a list of processes running in the container:

tests/integration/exec.bats

@@ -21,6 +21,26 @@ function teardown() {
 	[[ "${output}" == *"Hello from exec"* ]]
 }
 
+@test "runc exec [exit codes]" {
+	runc run -d --console-socket "$CONSOLE_SOCKET" test_busybox
+	[ "$status" -eq 0 ]
+
+	runc exec test_busybox false
+	[ "$status" -eq 1 ]
+
+	runc exec test_busybox sh -c "exit 42"
+	[ "$status" -eq 42 ]
+
+	runc exec --pid-file /non-existent/directory test_busybox true
+	[ "$status" -eq 255 ]
+
+	runc exec test_busybox no-such-binary
+	[ "$status" -eq 255 ]
+
+	runc exec no_such_container true
+	[ "$status" -eq 255 ]
+}
+
 @test "runc exec --pid-file" {
 	# run busybox detached
 	runc run -d --console-socket "$CONSOLE_SOCKET" test_busybox

utils.go

@@ -53,13 +53,17 @@ func logrusToStderr() bool {
 // fatal prints the error's details if it is a libcontainer specific error type
 // then exits the program with an exit status of 1.
 func fatal(err error) {
-	// make sure the error is written to the logger
+	fatalWithCode(err, 1)
+}
+
+func fatalWithCode(err error, ret int) {
+	// Make sure the error is written to the logger.
 	logrus.Error(err)
 	if !logrusToStderr() {
 		fmt.Fprintln(os.Stderr, err)
 	}
 
-	os.Exit(1)
+	os.Exit(ret)
 }
 
 // setupSpec performs initial setup based on the cli.Context for the container