Add a 60s timeout to shell_command to prevent processes from building up (#38491)

If a process never ended, there was not timeout and they would
build up in the background until Home Assistant crashed.

homeassistant/components/shell_command/__init__.py

@@ -12,6 +12,8 @@ from homeassistant.helpers.typing import ConfigType, HomeAssistantType
 
 DOMAIN = "shell_command"
 
+COMMAND_TIMEOUT = 60
+
 _LOGGER = logging.getLogger(__name__)
 
 CONFIG_SCHEMA = vol.Schema(
@@ -74,7 +76,22 @@ async def async_setup(hass: HomeAssistantType, config: ConfigType) -> bool:
             )
 
         process = await create_process
-        stdout_data, stderr_data = await process.communicate()
+        try:
+            stdout_data, stderr_data = await asyncio.wait_for(
+                process.communicate(), COMMAND_TIMEOUT
+            )
+        except asyncio.TimeoutError:
+            _LOGGER.exception(
+                "Timed out running command: `%s`, after: %ss", cmd, COMMAND_TIMEOUT
+            )
+            if process:
+                try:
+                    await process.kill()
+                except TypeError:
+                    pass
+                del process
+
+            return
 
         if stdout_data:
             _LOGGER.debug(

tests/components/shell_command/test_init.py

@@ -6,7 +6,7 @@ from typing import Tuple
 import unittest
 
 from homeassistant.components import shell_command
-from homeassistant.setup import setup_component
+from homeassistant.setup import async_setup_component, setup_component
 
 from tests.async_mock import Mock, patch
 from tests.common import get_test_home_assistant
@@ -178,3 +178,23 @@ class TestShellCommand(unittest.TestCase):
         self.hass.block_till_done()
         assert mock_output.call_count == 1
         assert test_phrase.encode() + b"\n" == mock_output.call_args_list[0][0][-1]
+
+
+async def test_do_no_run_forever(hass, caplog):
+    """Test subprocesses terminate after the timeout."""
+
+    with patch.object(shell_command, "COMMAND_TIMEOUT", 0.001):
+        assert await async_setup_component(
+            hass,
+            shell_command.DOMAIN,
+            {shell_command.DOMAIN: {"test_service": "sleep 10000"}},
+        )
+        await hass.async_block_till_done()
+
+        await hass.services.async_call(
+            shell_command.DOMAIN, "test_service", blocking=True
+        )
+        await hass.async_block_till_done()
+
+    assert "Timed out" in caplog.text
+    assert "sleep 10000" in caplog.text