Fixed #26691 -- Removed checking for a file's existence before deleting.

File operations always raise a ENOENT error when a file doesn't exist.
Checking the file exists before the operation adds a race condition
condition where the file could be removed between operations. As the
operation already raises an error on a missing file, avoid this race and
avoid checking the file exists twice. Instead only check a file exists
by catching the ENOENT error.

1 files changed, 7 insertions, 8 deletions

diff --git a/django/core/cache/backends/filebased.py b/django/core/cache/backends/filebased.py
index 2a8b24ddfc..bff912d85d 100644
--- a/django/core/cache/backends/filebased.py
+++ b/django/core/cache/backends/filebased.py
@@ -35,14 +35,13 @@ class FileBasedCache(BaseCache):
 
     def get(self, key, default=None, version=None):
         fname = self._key_to_file(key, version)
-        if os.path.exists(fname):
-            try:
-                with io.open(fname, 'rb') as f:
-                    if not self._is_expired(f):
-                        return pickle.loads(zlib.decompress(f.read()))
-            except IOError as e:
-                if e.errno == errno.ENOENT:
-                    pass  # Cache file was removed after the exists check
+        try:
+            with io.open(fname, 'rb') as f:
+                if not self._is_expired(f):
+                    return pickle.loads(zlib.decompress(f.read()))
+        except IOError as e:
+            if e.errno == errno.ENOENT:
+                pass  # Cache file doesn't exist.
         return default
 
     def set(self, key, value, timeout=DEFAULT_TIMEOUT, version=None):