From 32268456d6494483f9a737dc7c32bbbf1eceab8c Mon Sep 17 00:00:00 2001
From: Marti Raudsepp <marti@juffo.org>
Date: Tue, 13 Dec 2022 11:20:25 +0200
Subject: [PATCH] Fixed #34209 -- Prevented FileBasedCache.has_key() crash
 caused by a race condition.

---
 django/core/cache/backends/filebased.py | 5 +++--
 tests/cache/tests.py                    | 6 ++++++
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/django/core/cache/backends/filebased.py b/django/core/cache/backends/filebased.py
index 631da49444..215fefbcc0 100644
--- a/django/core/cache/backends/filebased.py
+++ b/django/core/cache/backends/filebased.py
@@ -90,10 +90,11 @@ class FileBasedCache(BaseCache):
 
     def has_key(self, key, version=None):
         fname = self._key_to_file(key, version)
-        if os.path.exists(fname):
+        try:
             with open(fname, "rb") as f:
                 return not self._is_expired(f)
-        return False
+        except FileNotFoundError:
+            return False
 
     def _cull(self):
         """
diff --git a/tests/cache/tests.py b/tests/cache/tests.py
index 937a55acc5..c4d4522514 100644
--- a/tests/cache/tests.py
+++ b/tests/cache/tests.py
@@ -1762,6 +1762,12 @@ class FileBasedCacheTests(BaseCacheTests, TestCase):
         with open(cache_file, "rb") as fh:
             self.assertIs(cache._is_expired(fh), True)
 
+    def test_has_key_race_handling(self):
+        self.assertIs(cache.add("key", "value"), True)
+        with mock.patch("builtins.open", side_effect=FileNotFoundError) as mocked_open:
+            self.assertIs(cache.has_key("key"), False)
+            mocked_open.assert_called_once()
+
 
 @unittest.skipUnless(RedisCache_params, "Redis backend not configured")
 @override_settings(